antliscence/src/main/org/apache/tools/ant/IntrospectionHelper.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.tools.ant;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import org.apache.tools.ant.types.EnumeratedAttribute;
import org.apache.tools.ant.taskdefs.PreSetDef;
import org.apache.tools.ant.util.StringUtils;

/**
 * Helper class that collects the methods a task or nested element
 * holds to set attributes, create nested elements or hold PCDATA
 * elements.
 *
 * It contains hashtables containing classes that use introspection
 * to handle all the invocation of the project-component specific methods.
 *
 * This class is somewhat complex, as it implements the O/X mapping between
 * Ant XML and Java class instances. This is not the best place for someone new
 * to Ant to start contributing to the codebase, as a change here can break the
 * entire system in interesting ways. Always run a full test of Ant before checking
 * in/submitting changes to this file.
 *
 * The class is final and has a private constructor.
 * To get an instance for a specific (class,project) combination,
 * use {@link #getHelper(Project,Class)}.
 * This may return an existing version, or a new one
 * ...do not make any assumptions about its uniqueness, or its validity after the Project
 * instance has finished its build.
 *
 */
public final class IntrospectionHelper  {

    /**
     * Helper instances we've already created (Class.getName() to IntrospectionHelper).
     */
    private static final Map HELPERS = new Hashtable();

    /**
     * Map from primitive types to wrapper classes for use in
     * createAttributeSetter (Class to Class). Note that char
     * and boolean are in here even though they get special treatment
     * - this way we only need to test for the wrapper class.
     */
    private static final Map PRIMITIVE_TYPE_MAP = new HashMap(8);

    // Set up PRIMITIVE_TYPE_MAP
    static {
        Class[] primitives = {Boolean.TYPE, Byte.TYPE, Character.TYPE, Short.TYPE,
                              Integer.TYPE, Long.TYPE, Float.TYPE, Double.TYPE};
        Class[] wrappers = {Boolean.class, Byte.class, Character.class, Short.class,
                            Integer.class, Long.class, Float.class, Double.class};
        for (int i = 0; i < primitives.length; i++) {
            PRIMITIVE_TYPE_MAP.put (primitives[i], wrappers[i]);
        }
    }

    private static final int MAX_REPORT_NESTED_TEXT = 20;
    private static final String ELLIPSIS = "...";

    /**
     * Map from attribute names to attribute types
     * (String to Class).
     */
    private Hashtable attributeTypes = new Hashtable();

    /**
     * Map from attribute names to attribute setter methods
     * (String to AttributeSetter).
     */
    private Hashtable attributeSetters = new Hashtable();

    /**
     * Map from attribute names to nested types
     * (String to Class).
     */
    private Hashtable nestedTypes = new Hashtable();

    /**
     * Map from attribute names to methods to create nested types
     * (String to NestedCreator).
     */
    private Hashtable nestedCreators = new Hashtable();

    /**
     * Vector of methods matching add[Configured](Class) pattern.
     */
    private List addTypeMethods = new ArrayList();

    /**
     * The method to invoke to add PCDATA.
     */
    private Method addText = null;

    /**
     * The class introspected by this instance.
     */
    private Class bean;

    /**
     * Sole constructor, which is private to ensure that all
     * IntrospectionHelpers are created via {@link #getHelper(Class) getHelper}.
     * Introspects the given class for bean-like methods.
     * Each method is examined in turn, and the following rules are applied:
     * <p>
     * <ul>
     * <li>If the method is <code>Task.setLocation(Location)</code>,
     * <code>Task.setTaskType(String)</code>
     * or <code>TaskContainer.addTask(Task)</code>, it is ignored. These
     * methods are handled differently elsewhere.
     * <li><code>void addText(String)</code> is recognised as the method for
     * adding PCDATA to a bean.
     * <li><code>void setFoo(Bar)</code> is recognised as a method for
     * setting the value of attribute <code>foo</code>, so long as
     * <code>Bar</code> is non-void and is not an array type. Non-String
     * parameter types always overload String parameter types, but that is
     * the only guarantee made in terms of priority.
     * <li><code>Foo createBar()</code> is recognised as a method for
     * creating a nested element called <code>bar</code> of type
     * <code>Foo</code>, so long as <code>Foo</code> is not a primitive or
     * array type.
     * <li><code>void addConfiguredFoo(Bar)</code> is recognised as a
     * method for storing a pre-configured element called
     * <code>foo</code> and of type <code>Bar</code>, so long as
     * <code>Bar</code> is not an array, primitive or String type.
     * <code>Bar</code> must have an accessible constructor taking no
     * arguments.
     * <li><code>void addFoo(Bar)</code> is recognised as a method for storing
     * an element called <code>foo</code> and of type <code>Bar</code>, so
     * long as <code>Bar</code> is not an array, primitive or String type.
     * <code>Bar</code> must have an accessible constructor taking no
     * arguments. This is distinct from the 'addConfigured' idiom in that
     * the nested element is added to the parent immediately after it is
     * constructed; in practice this means that <code>addFoo(Bar)</code> should
     * do little or nothing with its argument besides storing it for later use.
     * </ul>
     * Note that only one method is retained to create/set/addConfigured/add
     * any element or attribute.
     *
     * @param bean The bean type to introspect.
     *             Must not be <code>null</code>.
     *
     * @see #getHelper(Class)
     */
    private IntrospectionHelper(final Class bean) {
        this.bean = bean;
        Method[] methods = bean.getMethods();
        for (int i = 0; i < methods.length; i++) {
            final Method m = methods[i];
            final String name = m.getName();
            Class returnType = m.getReturnType();
            Class[] args = m.getParameterTypes();

            // check of add[Configured](Class) pattern
            if (args.length == 1 && java.lang.Void.TYPE.equals(returnType)
                    && ("add".equals(name) || "addConfigured".equals(name))) {
                insertAddTypeMethod(m);
                continue;
            }
            // not really user settable properties on tasks/project components
            if (org.apache.tools.ant.ProjectComponent.class.isAssignableFrom(bean)
                    && args.length == 1 && isHiddenSetMethod(name, args[0])) {
                continue;
            }
            // hide addTask for TaskContainers
            if (isContainer() && args.length == 1 && "addTask".equals(name)
                    && org.apache.tools.ant.Task.class.equals(args[0])) {
                continue;
            }
            if ("addText".equals(name) && java.lang.Void.TYPE.equals(returnType)
                    && args.length == 1 && java.lang.String.class.equals(args[0])) {
                addText = methods[i];
            } else if (name.startsWith("set") && java.lang.Void.TYPE.equals(returnType)
                    && args.length == 1 && !args[0].isArray()) {
                String propName = getPropertyName(name, "set");
                if (attributeSetters.get(propName) != null) {
                    if (java.lang.String.class.equals(args[0])) {
                        /*
                            Ignore method m, as there is an overloaded
                            form of this method that takes in a
                            non-string argument, which gains higher
                            priority.
                        */
                        continue;
                    }
                    /*
                        If the argument is not a String and if there
                        is an overloaded form of this method already defined,
                        we just override that with the new one.
                        This mechanism does not guarantee any specific order
                        in which the methods will be selected: so any code
                        that depends on the order in which "set" methods have
                        been defined, is not guaranteed to be selected in any
                        particular order.
                    */
                }
                AttributeSetter as = createAttributeSetter(m, args[0], propName);
                if (as != null) {
                    attributeTypes.put(propName, args[0]);
                    attributeSetters.put(propName, as);
                }
            } else if (name.startsWith("create") && !returnType.isArray()
                    && !returnType.isPrimitive() && args.length == 0) {

                String propName = getPropertyName(name, "create");
                // Check if a create of this property is already present
                // add takes preference over create for CB purposes
                if (nestedCreators.get(propName) == null) {
                    nestedTypes.put(propName, returnType);
                    nestedCreators.put(propName, new CreateNestedCreator(m));
                }
            } else if (name.startsWith("addConfigured")
                    && java.lang.Void.TYPE.equals(returnType) && args.length == 1
                    && !java.lang.String.class.equals(args[0])
                    && !args[0].isArray() && !args[0].isPrimitive()) {
                try {
                    Constructor constructor = null;
                    try {
                        constructor = args[0].getConstructor(new Class[] {});
                    } catch (NoSuchMethodException ex) {
                        constructor = args[0].getConstructor(new Class[] {Project.class});
                    }
                    String propName = getPropertyName(name, "addConfigured");
                    nestedTypes.put(propName, args[0]);
                    nestedCreators.put(propName, new AddNestedCreator(m,
                        constructor, AddNestedCreator.ADD_CONFIGURED));
                } catch (NoSuchMethodException nse) {
                    // ignore
                }
            } else if (name.startsWith("add")
                    && java.lang.Void.TYPE.equals(returnType) && args.length == 1
                    && !java.lang.String.class.equals(args[0])
                    && !args[0].isArray() && !args[0].isPrimitive()) {
                try {
                    Constructor constructor = null;
                    try {
                        constructor = args[0].getConstructor(new Class[] {});
                    } catch (NoSuchMethodException ex) {
                        constructor = args[0].getConstructor(new Class[] {Project.class});
                    }
                    String propName = getPropertyName(name, "add");
                    if (nestedTypes.get(propName) != null) {
                        /*
                         *  Ignore this method as there is an addConfigured
                         *  form of this method that has a higher
                         *  priority
                         */
                        continue;
                    }
                    nestedTypes.put(propName, args[0]);
                    nestedCreators.put(propName, new AddNestedCreator(m,
                            constructor, AddNestedCreator.ADD));
                } catch (NoSuchMethodException nse) {
                    // ignore
                }
            }
        }
    }

    /**
     * Certain set methods are part of the Ant core interface to tasks and
     * therefore not to be considered for introspection
     *
     * @param name the name of the set method
     * @param type the type of the set method's parameter
     * @return true if the given set method is to be hidden.
     */
    private boolean isHiddenSetMethod(String name, Class type) {
        if ("setLocation".equals(name) && org.apache.tools.ant.Location.class.equals(type)) {
            return true;
        }
        if ("setTaskType".equals(name) && java.lang.String.class.equals(type)) {
            return true;
        }
        return false;
    }

    /**
     * Returns a helper for the given class, either from the cache
     * or by creating a new instance.
     *
     * @param c The class for which a helper is required.
     *          Must not be <code>null</code>.
     *
     * @return a helper for the specified class
     */
    public static synchronized IntrospectionHelper getHelper(Class c) {
        return getHelper(null, c);
    }

    /**
     * Returns a helper for the given class, either from the cache
     * or by creating a new instance.
     *
     * The method will make sure the helper will be cleaned up at the end of
     * the project, and only one instance will be created for each class.
     *
     * @param p the project instance. Can be null, in which case the helper is not cached.
     * @param c The class for which a helper is required.
     *          Must not be <code>null</code>.
     *
     * @return a helper for the specified class
     */
    public static IntrospectionHelper getHelper(Project p, Class c) {
        IntrospectionHelper ih = (IntrospectionHelper) HELPERS.get(c.getName());
        // If a helper cannot be found, or if the helper is for another
        // classloader, create a new IH
        if (ih == null || ih.bean != c) {
            ih = new IntrospectionHelper(c);
            if (p != null) {
                // #30162: do *not* cache this if there is no project, as we
                // cannot guarantee that the cache will be cleared.
                HELPERS.put(c.getName(), ih);
            }
        }
        return ih;
    }

    /**
     * Sets the named attribute in the given element, which is part of the
     * given project.
     *
     * @param p The project containing the element. This is used when files
     *          need to be resolved. Must not be <code>null</code>.
     * @param element The element to set the attribute in. Must not be
     *                <code>null</code>.
     * @param attributeName The name of the attribute to set. Must not be
     *                      <code>null</code>.
     * @param value The value to set the attribute to. This may be interpreted
     *              or converted to the necessary type if the setter method
     *              doesn't accept an object of the supplied type.
     *
     * @exception BuildException if the introspected class doesn't support
     *                           the given attribute, or if the setting
     *                           method fails.
     */
    public void setAttribute(Project p, Object element, String attributeName,
            Object value) throws BuildException {
        AttributeSetter as = (AttributeSetter) attributeSetters.get(
                attributeName.toLowerCase(Locale.US));
        if (as == null && value != null) {
            if (element instanceof DynamicAttributeNS) {
                DynamicAttributeNS dc = (DynamicAttributeNS) element;
                String uriPlusPrefix = ProjectHelper.extractUriFromComponentName(attributeName);
                String uri = ProjectHelper.extractUriFromComponentName(uriPlusPrefix);
                String localName = ProjectHelper.extractNameFromComponentName(attributeName);
                String qName = "".equals(uri) ? localName : uri + ":" + localName;
                dc.setDynamicAttribute(uri, localName, qName, value.toString());
                return;
            }
            if (element instanceof DynamicAttribute) {
                DynamicAttribute dc = (DynamicAttribute) element;
                dc.setDynamicAttribute(attributeName.toLowerCase(Locale.US), value.toString());
                return;
            }
            if (attributeName.indexOf(':') >= 0) {
                return; // Ignore attribute from unknown uri's
            }
            String msg = getElementName(p, element)
                    + " doesn't support the \"" + attributeName + "\" attribute.";
            throw new UnsupportedAttributeException(msg, attributeName);
        }
        try {
            as.setObject(p, element, value);
        } catch (IllegalAccessException ie) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ie);
        } catch (InvocationTargetException ite) {
            throw extractBuildException(ite);
        }
    }

    /**
     * Sets the named attribute in the given element, which is part of the
     * given project.
     *
     * @param p The project containing the element. This is used when files
     *          need to be resolved. Must not be <code>null</code>.
     * @param element The element to set the attribute in. Must not be
     *                <code>null</code>.
     * @param attributeName The name of the attribute to set. Must not be
     *                      <code>null</code>.
     * @param value The value to set the attribute to. This may be interpreted
     *              or converted to the necessary type if the setter method
     *              doesn't just take a string. Must not be <code>null</code>.
     *
     * @exception BuildException if the introspected class doesn't support
     *                           the given attribute, or if the setting
     *                           method fails.
     */
    public void setAttribute(Project p, Object element, String attributeName,
                             String value) throws BuildException {
        setAttribute(p, element, attributeName, (Object) value);
    }

    /**
     * Adds PCDATA to an element, using the element's
     * <code>void addText(String)</code> method, if it has one. If no
     * such method is present, a BuildException is thrown if the
     * given text contains non-whitespace.
     *
     * @param project The project which the element is part of.
     *                Must not be <code>null</code>.
     * @param element The element to add the text to.
     *                Must not be <code>null</code>.
     * @param text    The text to add.
     *                Must not be <code>null</code>.
     *
     * @exception BuildException if non-whitespace text is provided and no
     *                           method is available to handle it, or if
     *                           the handling method fails.
     */
    public void addText(Project project, Object element, String text)
        throws BuildException {
        if (addText == null) {
            text = text.trim();
            // Element doesn't handle text content
            if (text.length() == 0) {
                // Only whitespace - ignore
                return;
            }
            // Not whitespace - fail
            throw new BuildException(project.getElementName(element)
                    + " doesn't support nested text data (\"" + condenseText(text) + "\").");
        }
        try {
            addText.invoke(element, new Object[] {text});
        } catch (IllegalAccessException ie) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ie);
        } catch (InvocationTargetException ite) {
            throw extractBuildException(ite);
        }
    }

    /**
     * Utility method to throw a NotSupported exception
     *
     * @param project the Project instance.
     * @param parent the object which doesn't support a requested element
     * @param elementName the name of the Element which is trying to be created.
     */
    public void throwNotSupported(Project project, Object parent, String elementName) {
        String msg = project.getElementName(parent)
                + " doesn't support the nested \"" + elementName + "\" element.";
        throw new UnsupportedElementException(msg, elementName);
    }

    /**
     * Get the specific NestedCreator for a given project/parent/element combination
     * @param project ant project
     * @param parentUri URI of the parent.
     * @param parent the parent class
     * @param elementName element to work with. This can contain
     *  a URI,localname tuple of of the form uri:localname
     * @param child the bit of XML to work with
     * @return a nested creator that can handle the child elements.
     * @throws BuildException if the parent does not support child elements of that name
     */
    private NestedCreator getNestedCreator(
        Project project, String parentUri, Object parent,
        String elementName, UnknownElement child) throws BuildException {

        String uri = ProjectHelper.extractUriFromComponentName(elementName);
        String name = ProjectHelper.extractNameFromComponentName(elementName);

        if (uri.equals(ProjectHelper.ANT_CORE_URI)) {
            uri = "";
        }
        if (parentUri.equals(ProjectHelper.ANT_CORE_URI)) {
            parentUri = "";
        }
        NestedCreator nc = null;
        if (uri.equals(parentUri) || uri.length() == 0) {
            nc = (NestedCreator) nestedCreators.get(name.toLowerCase(Locale.US));
        }
        if (nc == null) {
            nc = createAddTypeCreator(project, parent, elementName);
        }
        if (nc == null && parent instanceof DynamicElementNS) {
            DynamicElementNS dc = (DynamicElementNS) parent;
            String qName = child == null ? name : child.getQName();
            final Object nestedElement = dc.createDynamicElement(
                    child == null ? "" : child.getNamespace(), name, qName);
            if (nestedElement != null) {
                nc = new NestedCreator(null) {
                    Object create(Project project, Object parent, Object ignore) {
                        return nestedElement;
                    }
                };
            }
        }
        if (nc == null && parent instanceof DynamicElement) {
            DynamicElement dc = (DynamicElement) parent;
            final Object nestedElement = dc.createDynamicElement(name.toLowerCase(Locale.US));
            if (nestedElement != null) {
                nc = new NestedCreator(null) {
                    Object create(Project project, Object parent, Object ignore) {
                        return nestedElement;
                    }
                };
            }
        }
        if (nc == null) {
            throwNotSupported(project, parent, elementName);
        }
        return nc;
    }

    /**
     * Creates a named nested element. Depending on the results of the
     * initial introspection, either a method in the given parent instance
     * or a simple no-arg constructor is used to create an instance of the
     * specified element type.
     *
     * @param project Project to which the parent object belongs.
     *                Must not be <code>null</code>. If the resulting
     *                object is an instance of ProjectComponent, its
     *                Project reference is set to this parameter value.
     * @param parent  Parent object used to create the instance.
     *                Must not be <code>null</code>.
     * @param elementName Name of the element to create an instance of.
     *                    Must not be <code>null</code>.
     *
     * @return an instance of the specified element type
     * @deprecated since 1.6.x.
     *             This is not a namespace aware method.
     *
     * @exception BuildException if no method is available to create the
     *                           element instance, or if the creating method fails.
     */
    public Object createElement(Project project, Object parent, String elementName)
            throws BuildException {
        NestedCreator nc = getNestedCreator(project, "", parent, elementName, null);
        try {
            Object nestedElement = nc.create(project, parent, null);
            if (project != null) {
                project.setProjectReference(nestedElement);
            }
            return nestedElement;
        } catch (IllegalAccessException ie) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ie);
        } catch (InstantiationException ine) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ine);
        } catch (InvocationTargetException ite) {
            throw extractBuildException(ite);
        }
    }

    /**
     * returns an object that creates and stores an object
     * for an element of a parent.
     *
     * @param project      Project to which the parent object belongs.
     * @param parentUri    The namespace uri of the parent object.
     * @param parent       Parent object used to create the creator object to
     *                     create and store and instance of a subelement.
     * @param elementName  Name of the element to create an instance of.
     * @param ue           The unknown element associated with the element.
     * @return a creator object to create and store the element instance.
     */
    public Creator getElementCreator(
        Project project, String parentUri, Object parent, String elementName, UnknownElement ue) {
        NestedCreator nc = getNestedCreator(project, parentUri, parent, elementName, ue);
        return new Creator(project, parent, nc);
    }

    /**
     * Indicates whether the introspected class is a dynamic one,
     * supporting arbitrary nested elements and/or attributes.
     *
     * @return <code>true<code> if the introspected class is dynamic;
     *         <code>false<code> otherwise.
     * @since Ant 1.6.3
     *
     * @see DynamicElement
     * @see DynamicElementNS
     */
    public boolean isDynamic() {
        return DynamicElement.class.isAssignableFrom(bean)
                || DynamicElementNS.class.isAssignableFrom(bean);
    }

    /**
     * Indicates whether the introspected class is a task container,
     * supporting arbitrary nested tasks/types.
     *
     * @return <code>true<code> if the introspected class is a container;
     *         <code>false<code> otherwise.
     * @since Ant 1.6.3
     *
     * @see TaskContainer
     */
    public boolean isContainer() {
        return TaskContainer.class.isAssignableFrom(bean);
    }

    /**
     * Indicates if this element supports a nested element of the
     * given name.
     *
     * @param elementName the name of the nested element being checked
     *
     * @return true if the given nested element is supported
     */
    public boolean supportsNestedElement(String elementName) {
        return supportsNestedElement("", elementName);
    }

    /**
     * Indicate if this element supports a nested element of the
     * given name.
     *
     * @param parentUri   the uri of the parent
     * @param elementName the name of the nested element being checked
     *
     * @return true if the given nested element is supported
     */
    public boolean supportsNestedElement(String parentUri, String elementName) {
        if (isDynamic() || addTypeMethods.size() > 0) {
            return true;
        }
        String name = ProjectHelper.extractNameFromComponentName(elementName);
        if (!nestedCreators.containsKey(name.toLowerCase(Locale.US))) {
            return false;
        }
        String uri = ProjectHelper.extractUriFromComponentName(elementName);
        if (uri.equals(ProjectHelper.ANT_CORE_URI)) {
            uri = "";
        }
        if ("".equals(uri)) {
            return true;
        }
        if (parentUri.equals(ProjectHelper.ANT_CORE_URI)) {
            parentUri = "";
        }
        return uri.equals(parentUri);
    }

    /**
     * Stores a named nested element using a storage method determined
     * by the initial introspection. If no appropriate storage method
     * is available, this method returns immediately.
     *
     * @param project Ignored in this implementation.
     *                May be <code>null</code>.
     *
     * @param parent  Parent instance to store the child in.
     *                Must not be <code>null</code>.
     *
     * @param child   Child instance to store in the parent.
     *                Should not be <code>null</code>.
     *
     * @param elementName  Name of the child element to store.
     *                     May be <code>null</code>, in which case
     *                     this method returns immediately.
     *
     * @exception BuildException if the storage method fails.
     */
    public void storeElement(Project project, Object parent, Object child,
        String elementName) throws BuildException {
        if (elementName == null) {
            return;
        }
        NestedCreator ns = (NestedCreator) nestedCreators.get(elementName.toLowerCase(Locale.US));
        if (ns == null) {
            return;
        }
        try {
            ns.store(parent, child);
        } catch (IllegalAccessException ie) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ie);
        } catch (InstantiationException ine) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ine);
        } catch (InvocationTargetException ite) {
            throw extractBuildException(ite);
        }
    }

    /**
     * Helper method to extract the inner fault from an {@link InvocationTargetException}, and turn
     * it into a BuildException. If it is already a BuildException, it is type cast and returned; if
     * not a new BuildException is created containing the child as nested text.
     * @param ite
     * @return the nested exception
     */
    private static BuildException extractBuildException(InvocationTargetException ite) {
        Throwable t = ite.getTargetException();
        if (t instanceof BuildException) {
            return (BuildException) t;
        }
        return new BuildException(t);
    }

    /**
     * Returns the type of a named nested element.
     *
     * @param elementName The name of the element to find the type of.
     *                    Must not be <code>null</code>.
     *
     * @return the type of the nested element with the specified name.
     *         This will never be <code>null</code>.
     *
     * @exception BuildException if the introspected class does not
     *                           support the named nested element.
     */
    public Class getElementType(String elementName) throws BuildException {
        Class nt = (Class) nestedTypes.get(elementName);
        if (nt == null) {
            throw new UnsupportedElementException("Class "
                    + bean.getName() + " doesn't support the nested \""
                    + elementName + "\" element.", elementName);
        }
        return nt;
    }

    /**
     * Returns the type of a named attribute.
     *
     * @param attributeName The name of the attribute to find the type of.
     *                      Must not be <code>null</code>.
     *
     * @return the type of the attribute with the specified name.
     *         This will never be <code>null</code>.
     *
     * @exception BuildException if the introspected class does not
     *                           support the named attribute.
     */
    public Class getAttributeType(String attributeName) throws BuildException {
        Class at = (Class) attributeTypes.get(attributeName);
        if (at == null) {
            throw new UnsupportedAttributeException("Class "
                    + bean.getName() + " doesn't support the \""
                    + attributeName + "\" attribute.", attributeName);
        }
        return at;
    }

    /**
     * Returns the addText method when the introspected
     * class supports nested text.
     *
     * @return the method on this introspected class that adds nested text.
     *         Cannot be <code>null</code>.
     * @throws BuildException if the introspected class does not
     *         support the nested text.
     * @since Ant 1.6.3
     */
    public Method getAddTextMethod() throws BuildException {
        if (!supportsCharacters()) {
            throw new BuildException("Class " + bean.getName()
                    + " doesn't support nested text data.");
        }
        return addText;
    }

    /**
     * Returns the adder or creator method of a named nested element.
     *
     * @param  elementName The name of the attribute to find the setter
     *         method of. Must not be <code>null</code>.
     * @return the method on this introspected class that adds or creates this
     *         nested element. Can be <code>null</code> when the introspected
     *         class is a dynamic configurator!
     * @throws BuildException if the introspected class does not
     *         support the named nested element.
     * @since Ant 1.6.3
     */
    public Method getElementMethod(String elementName) throws BuildException {
        Object creator = nestedCreators.get(elementName);
        if (creator == null) {
            throw new UnsupportedElementException("Class "
                    + bean.getName() + " doesn't support the nested \""
                    + elementName + "\" element.", elementName);
        }
        return ((NestedCreator) creator).method;
    }

    /**
     * Returns the setter method of a named attribute.
     *
     * @param  attributeName The name of the attribute to find the setter
     *         method of. Must not be <code>null</code>.
     * @return the method on this introspected class that sets this attribute.
     *         This will never be <code>null</code>.
     * @throws BuildException if the introspected class does not
     *         support the named attribute.
     * @since Ant 1.6.3
     */
    public Method getAttributeMethod(String attributeName) throws BuildException {
        Object setter = attributeSetters.get(attributeName);
        if (setter == null) {
            throw new UnsupportedAttributeException("Class "
                    + bean.getName() + " doesn't support the \""
                    + attributeName + "\" attribute.", attributeName);
        }
        return ((AttributeSetter) setter).method;
    }

    /**
     * Returns whether or not the introspected class supports PCDATA.
     *
     * @return whether or not the introspected class supports PCDATA.
     */
    public boolean supportsCharacters() {
        return addText != null;
    }

    /**
     * Returns an enumeration of the names of the attributes supported by the introspected class.
     *
     * @return an enumeration of the names of the attributes supported by the introspected class.
     * @see #getAttributeMap
     */
    public Enumeration getAttributes() {
        return attributeSetters.keys();
    }

    /**
     * Returns a read-only map of attributes supported by the introspected class.
     *
     * @return an attribute name to attribute <code>Class</code>
     *         unmodifiable map. Can be empty, but never <code>null</code>.
     * @since Ant 1.6.3
     */
    public Map getAttributeMap() {
        return attributeTypes.isEmpty()
            ? Collections.EMPTY_MAP : Collections.unmodifiableMap(attributeTypes);
    }

    /**
     * Returns an enumeration of the names of the nested elements supported
     * by the introspected class.
     *
     * @return an enumeration of the names of the nested elements supported
     *         by the introspected class.
     * @see #getNestedElementMap
     */
    public Enumeration getNestedElements() {
        return nestedTypes.keys();
    }

    /**
     * Returns a read-only map of nested elements supported
     * by the introspected class.
     *
     * @return a nested-element name to nested-element <code>Class</code>
     *         unmodifiable map. Can be empty, but never <code>null</code>.
     * @since Ant 1.6.3
     */
    public Map getNestedElementMap() {
        return nestedTypes.isEmpty()
            ? Collections.EMPTY_MAP : Collections.unmodifiableMap(nestedTypes);
    }

    /**
     * Returns a read-only list of extension points supported
     * by the introspected class.
     * <p>
     * A task/type or nested element with void methods named <code>add()<code>
     * or <code>addConfigured()</code>, taking a single class or interface
     * argument, supports extensions point. This method returns the list of
     * all these <em>void add[Configured](type)</em> methods.
     *
     * @return a list of void, single argument add() or addConfigured()
     *         <code>Method<code>s of all supported extension points.
     *         These methods are sorted such that if the argument type of a
     *         method derives from another type also an argument of a method
     *         of this list, the method with the most derived argument will
     *         always appear first. Can be empty, but never <code>null</code>.
     * @since Ant 1.6.3
     */
    public List getExtensionPoints() {
        return addTypeMethods.isEmpty()
                ? Collections.EMPTY_LIST : Collections.unmodifiableList(addTypeMethods);
    }

    /**
     * Creates an implementation of AttributeSetter for the given
     * attribute type. Conversions (where necessary) are automatically
     * made for the following types:
     * <ul>
     * <li>String (left as it is)
     * <li>Character/char (first character is used)
     * <li>Boolean/boolean
     * ({@link Project#toBoolean(String) Project.toBoolean(String)} is used)
     * <li>Class (Class.forName is used)
     * <li>File (resolved relative to the appropriate project)
     * <li>Path (resolve relative to the appropriate project)
     * <li>EnumeratedAttribute (uses its own
     * {@link EnumeratedAttribute#setValue(String) setValue} method)
     * <li>Other primitive types (wrapper classes are used with constructors
     * taking String)
     * </ul>
     *
     * If none of the above covers the given parameters, a constructor for the
     * appropriate class taking a String parameter is used if it is available.
     *
     * @param m The method to invoke on the bean when the setter is invoked.
     *          Must not be <code>null</code>.
     * @param arg The type of the single argument of the bean's method.
     *            Must not be <code>null</code>.
     * @param attrName the name of the attribute for which the setter is being
     *                 created.
     *
     * @return an appropriate AttributeSetter instance, or <code>null</code>
     *         if no appropriate conversion is available.
     */
    private AttributeSetter createAttributeSetter(final Method m,
                                                  Class arg,
                                                  final String attrName) {
        // use wrappers for primitive classes, e.g. int and
        // Integer are treated identically
        final Class reflectedArg = PRIMITIVE_TYPE_MAP.containsKey(arg)
            ? (Class) PRIMITIVE_TYPE_MAP.get(arg) : arg;

        // simplest case - setAttribute expects String
        if (java.lang.String.class.equals(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                    m.invoke(parent, (Object[]) new String[] {value});
                }
            };
        }
        // char and Character get special treatment - take the first character
        if (java.lang.Character.class.equals(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                    if (value.length() == 0) {
                        throw new BuildException("The value \"\" is not a "
                                + "legal value for attribute \"" + attrName + "\"");
                    }
                    m.invoke(parent, (Object[]) new Character[] {new Character(value.charAt(0))});
                }
            };
        }
        // boolean and Boolean get special treatment because we have a nice method in Project
        if (java.lang.Boolean.class.equals(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                    m.invoke(parent, (Object[]) new Boolean[] {
                            Project.toBoolean(value) ? Boolean.TRUE : Boolean.FALSE });
                }
            };
        }
        // Class doesn't have a String constructor but a decent factory method
        if (java.lang.Class.class.equals(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException, BuildException {
                    try {
                        m.invoke(parent, new Object[] {Class.forName(value)});
                    } catch (ClassNotFoundException ce) {
                        throw new BuildException(ce);
                    }
                }
            };
        }
        // resolve relative paths through Project
        if (java.io.File.class.equals(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                    m.invoke(parent, new Object[] {p.resolveFile(value)});
                }
            };
        }
        // EnumeratedAttributes have their own helper class
        if (EnumeratedAttribute.class.isAssignableFrom(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException, BuildException {
                    try {
                        EnumeratedAttribute ea = (EnumeratedAttribute) reflectedArg.newInstance();
                        ea.setValue(value);
                        m.invoke(parent, new Object[] {ea});
                    } catch (InstantiationException ie) {
                        throw new BuildException(ie);
                    }
                }
            };
        }

        AttributeSetter setter = getEnumSetter(reflectedArg, m, arg);
        if (setter != null) {
            return setter;
        }

        if (java.lang.Long.class.equals(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException, BuildException {
                    try {
                        m.invoke(parent, new Object[] {
                                new Long(StringUtils.parseHumanSizes(value)) });
                    } catch (InvocationTargetException e) {
                        throw e;
                    } catch (IllegalAccessException e) {
                        throw e;
                    } catch (Exception e) {
                        throw new BuildException(e);
                    }
                }
            };
        }
        // worst case. look for a public String constructor and use it
        // also supports new Whatever(Project, String) as for Path or Reference
        // This is used (deliberately) for all primitives/wrappers other than
        // char, boolean, and long.
        boolean includeProject;
        Constructor c;
        try {
            // First try with Project.
            c = reflectedArg.getConstructor(new Class[] {Project.class, String.class});
            includeProject = true;
        } catch (NoSuchMethodException nme) {
            // OK, try without.
            try {
                c = reflectedArg.getConstructor(new Class[] {String.class});
                includeProject = false;
            } catch (NoSuchMethodException nme2) {
                // Well, no matching constructor.
                return null;
            }
        }
        final boolean finalIncludeProject = includeProject;
        final Constructor finalConstructor = c;

        return new AttributeSetter(m, arg) {
            public void set(Project p, Object parent, String value)
                    throws InvocationTargetException, IllegalAccessException, BuildException {
                try {
                    Object[] args = finalIncludeProject
                            ? new Object[] {p, value} : new Object[] {value};

                    Object attribute = finalConstructor.newInstance(args);
                    if (p != null) {
                        p.setProjectReference(attribute);
                    }
                    m.invoke(parent, new Object[] {attribute});
                } catch (InstantiationException ie) {
                    throw new BuildException(ie);
                }
            }
        };
    }

    private AttributeSetter getEnumSetter(
        final Class reflectedArg, final Method m, Class arg) {
        Class enumClass = null;
        try {
            enumClass = Class.forName("java.lang.Enum");
        } catch (ClassNotFoundException e) {
            //ignore
        }
        if (enumClass != null && enumClass.isAssignableFrom(reflectedArg)) {
            return new AttributeSetter(m, arg) {
                public void set(Project p, Object parent, String value)
                    throws InvocationTargetException, IllegalAccessException,
                    BuildException {
                    try {
                        m.invoke(
                            parent, new Object[] {
                                reflectedArg.getMethod(
                                    "valueOf", new Class[] {String.class}).
                                invoke(null, new Object[] {value})});
                    } catch (InvocationTargetException x) {
                        //there is specific logic here for the value
                        // being out of the allowed set of enumerations.
                        if (x.getTargetException() instanceof IllegalArgumentException) {
                            throw new BuildException(
                                "'" + value + "' is not a permitted value for "
                                + reflectedArg.getName());
                        }
                        //only if the exception is not an IllegalArgument do we
                        // request the
                        //BuildException via extractBuildException():
                        throw extractBuildException(x);
                    } catch (Exception x) {
                        //any other failure of invoke() to work.
                        throw new BuildException(x);
                    }
                }
            };
        }
        return null;
    }

    /**
     * Returns a description of the type of the given element in
     * relation to a given project. This is used for logging purposes
     * when the element is asked to cope with some data it has no way of handling.
     *
     * @param project The project the element is defined in. Must not be <code>null</code>.
     *
     * @param element The element to describe. Must not be <code>null</code>.
     *
     * @return a description of the element type
     */
    private String getElementName(Project project, Object element) {
        return project.getElementName(element);
    }

    /**
     * Extracts the name of a property from a method name by subtracting
     * a given prefix and converting into lower case. It is up to calling
     * code to make sure the method name does actually begin with the
     * specified prefix - no checking is done in this method.
     *
     * @param methodName The name of the method in question. Must not be <code>null</code>.
     * @param prefix     The prefix to remove. Must not be <code>null</code>.
     *
     * @return the lower-cased method name with the prefix removed.
     */
    private static String getPropertyName(String methodName, String prefix) {
        return methodName.substring(prefix.length()).toLowerCase(Locale.US);
    }

    /**
     * creator - allows use of create/store external
     * to IntrospectionHelper.
     * The class is final as it has a private constructor.
     */
    public static final class Creator {
        private NestedCreator nestedCreator;
        private Object parent;
        private Project project;
        private Object nestedObject;
        private String polyType;

        /**
         * Creates a new Creator instance.
         * This object is given to the UnknownElement to create
         * objects for sub-elements. UnknownElement calls
         * create to create an object, the object then gets
         * configured and then UnknownElement calls store.
         * SetPolyType may be used to override the type used
         * to create the object with. SetPolyType gets called before create.
         *
         * @param project the current project
         * @param parent  the parent object to create the object in
         * @param nestedCreator the nested creator object to use
         */
        private Creator(Project project, Object parent, NestedCreator nestedCreator) {
            this.project = project;
            this.parent = parent;
            this.nestedCreator = nestedCreator;
        }

        /**
         * Used to override the class used to create the object.
         *
         * @param polyType a ant component type name
         */
        public void setPolyType(String polyType) {
            this.polyType = polyType;
        }

        /**
         * Create an object using this creator, which is determined by introspection.
         *
         * @return the created object
         */
        public Object create() {
            if (polyType != null) {
                if (!nestedCreator.isPolyMorphic()) {
                    throw new BuildException(
                            "Not allowed to use the polymorphic form for this element");
                }
                ComponentHelper helper = ComponentHelper.getComponentHelper(project);
                nestedObject = helper.createComponent(polyType);
                if (nestedObject == null) {
                    throw new BuildException("Unable to create object of type " + polyType);
                }
            }
            try {
                nestedObject = nestedCreator.create(project, parent, nestedObject);
                if (project != null) {
                    project.setProjectReference(nestedObject);
                }
                return nestedObject;
            } catch (IllegalAccessException ex) {
                throw new BuildException(ex);
            } catch (InstantiationException ex) {
                throw new BuildException(ex);
            } catch (IllegalArgumentException ex) {
                if (polyType == null) {
                    throw ex;
                }
                throw new BuildException("Invalid type used " + polyType);
            } catch (InvocationTargetException ex) {
                throw extractBuildException(ex);
            }
        }

        /**
         * @return the real object (used currently only for presetdef).
         */
        public Object getRealObject() {
            return nestedCreator.getRealObject();
        }

        /**
         * Stores the nested element object using a storage method determined by introspection.
         *
         */
        public void store() {
            try {
                nestedCreator.store(parent, nestedObject);
            } catch (IllegalAccessException ex) {
                throw new BuildException(ex);
            } catch (InstantiationException ex) {
                throw new BuildException(ex);
            } catch (IllegalArgumentException ex) {
                if (polyType == null) {
                    throw ex;
                }
                throw new BuildException("Invalid type used " + polyType);
            } catch (InvocationTargetException ex) {
                throw extractBuildException(ex);
            }
        }
    }

    /**
     * Internal interface used to create nested elements. Not documented
     * in detail for reasons of source code readability.
     */
    private abstract static class NestedCreator {
        private Method method; // the method called to add/create the nested element

        protected NestedCreator(Method m) {
            method = m;
        }
        Method getMethod() {
            return method;
        }
        boolean isPolyMorphic() {
            return false;
        }
        Object getRealObject() {
            return null;
        }
        abstract Object create(Project project, Object parent, Object child)
                throws InvocationTargetException, IllegalAccessException, InstantiationException;

        void store(Object parent, Object child)
                 throws InvocationTargetException, IllegalAccessException, InstantiationException {
            // DO NOTHING
        }
    }

    private static class CreateNestedCreator extends NestedCreator {
        CreateNestedCreator(Method m) {
            super(m);
        }

        Object create(Project project, Object parent, Object ignore)
                throws InvocationTargetException, IllegalAccessException {
            return getMethod().invoke(parent, new Object[] {});
        }
    }

    /** Version to use for addXXX and addConfiguredXXX */
    private static class AddNestedCreator extends NestedCreator {

        static final int ADD = 1;
        static final int ADD_CONFIGURED = 2;

        private Constructor constructor;
        private int behavior; // ADD or ADD_CONFIGURED

        AddNestedCreator(Method m, Constructor c, int behavior) {
            super(m);
            this.constructor = c;
            this.behavior = behavior;
        }

        boolean isPolyMorphic() {
            return true;
        }

        Object create(Project project, Object parent, Object child)
                throws InvocationTargetException, IllegalAccessException, InstantiationException {
            if (child == null) {
                child = constructor.newInstance(
                        constructor.getParameterTypes().length == 0
                                ? new Object[] {} : new Object[] {project});
            }
            if (child instanceof PreSetDef.PreSetDefinition) {
                child = ((PreSetDef.PreSetDefinition) child).createObject(project);
            }
            if (behavior == ADD) {
                istore(parent, child);
            }
            return child;
        }

        void store(Object parent, Object child)
                throws InvocationTargetException, IllegalAccessException, InstantiationException {
            if (behavior == ADD_CONFIGURED) {
                istore(parent, child);
            }
        }

        private void istore(Object parent, Object child)
                throws InvocationTargetException, IllegalAccessException, InstantiationException {
            getMethod().invoke(parent, new Object[] {child});
        }
    }

    /**
     * Internal interface used to setting element attributes. Not documented
     * in detail for reasons of source code readability.
     */
    private abstract static class AttributeSetter {
        private Method method; // the method called to set the attribute
        private Class type;
        protected AttributeSetter(Method m, Class type) {
            method = m;
            this.type = type;
        }
        void setObject(Project p, Object parent, Object value)
                throws InvocationTargetException, IllegalAccessException, BuildException {
            if (type != null) {
                Class useType = type;
                if (type.isPrimitive()) {
                    if (value == null) {
                        throw new BuildException(
                            "Attempt to set primitive "
                            + getPropertyName(method.getName(), "set")
                            + " to null on " + parent);
                    }
                    useType = (Class) PRIMITIVE_TYPE_MAP.get(type);
                }
                if (value == null || useType.isInstance(value)) {
                    method.invoke(parent, new Object[] {value});
                    return;
                }
            }
            set(p, parent, value.toString());
        }
        abstract void set(Project p, Object parent, String value)
                throws InvocationTargetException, IllegalAccessException, BuildException;
    }

    /**
     * Clears the static cache of on build finished.
     */
    public static void clearCache() {
        HELPERS.clear();
    }

    /**
     * Create a NestedCreator for the given element.
     * @param project owning project
     * @param parent Parent object used to create the instance.
     * @param elementName name of the element
     * @return a nested creator, or null if there is no component of the given name, or it
     *        has no matching add type methods
     * @throws BuildException
     */
    private NestedCreator createAddTypeCreator(
            Project project, Object parent, String elementName) throws BuildException {
        if (addTypeMethods.size() == 0) {
            return null;
        }
        ComponentHelper helper = ComponentHelper.getComponentHelper(project);

        MethodAndObject restricted =  createRestricted(
            helper, elementName, addTypeMethods);
        MethodAndObject topLevel = createTopLevel(
            helper, elementName, addTypeMethods);

        if (restricted == null && topLevel == null) {
            return null;
        }

        if (restricted != null && topLevel != null) {
            throw new BuildException(
                "ambiguous: type and component definitions for "
                + elementName);
        }

        MethodAndObject methodAndObject
            = restricted != null ? restricted : topLevel;

        Object rObject = methodAndObject.object;
        if (methodAndObject.object instanceof PreSetDef.PreSetDefinition) {
            rObject = ((PreSetDef.PreSetDefinition) methodAndObject.object)
                .createObject(project);
        }
        final Object nestedObject = methodAndObject.object;
        final Object realObject = rObject;

        return new NestedCreator(methodAndObject.method) {
            Object create(Project project, Object parent, Object ignore)
                    throws InvocationTargetException, IllegalAccessException {
                if (!getMethod().getName().endsWith("Configured")) {
                    getMethod().invoke(parent, new Object[] {realObject});
                }
                return nestedObject;
            }

            Object getRealObject() {
                return realObject;
            }

            void store(Object parent, Object child) throws InvocationTargetException,
                    IllegalAccessException, InstantiationException {
                if (getMethod().getName().endsWith("Configured")) {
                    getMethod().invoke(parent, new Object[] {realObject});
                }
            }
        };
    }

    /**
     * Inserts an add or addConfigured method into
     * the addTypeMethods array. The array is
     * ordered so that the more derived classes are first.
     * If both add and addConfigured are present, the addConfigured will take priority.
     * @param method the <code>Method</code> to insert.
     */
    private void insertAddTypeMethod(Method method) {
        Class argClass = method.getParameterTypes()[0];
        for (int c = 0; c < addTypeMethods.size(); ++c) {
            Method current = (Method) addTypeMethods.get(c);
            if (current.getParameterTypes()[0].equals(argClass)) {
                if (method.getName().equals("addConfigured")) {
                    // add configured replaces the add method
                    addTypeMethods.set(c, method);
                }
                return; // Already present
            }
            if (current.getParameterTypes()[0].isAssignableFrom(argClass)) {
                addTypeMethods.add(c, method);
                return; // higher derived
            }
        }
        addTypeMethods.add(method);
    }

    /**
     * Search the list of methods to find the first method
     * that has a parameter that accepts the nested element object.
     * @param paramClass the <code>Class</code> type to search for.
     * @param methods the <code>List</code> of methods to search.
     * @return a matching <code>Method</code>; null if none found.
     */
    private Method findMatchingMethod(Class paramClass, List methods) {
        if (paramClass == null) {
            return null;
        }
        Class matchedClass = null;
        Method matchedMethod = null;

        for (int i = 0; i < methods.size(); ++i) {
            Method method = (Method) methods.get(i);
            Class  methodClass = method.getParameterTypes()[0];
            if (methodClass.isAssignableFrom(paramClass)) {
                if (matchedClass == null) {
                    matchedClass = methodClass;
                    matchedMethod = method;
                } else if (!methodClass.isAssignableFrom(matchedClass)) {
                    throw new BuildException("ambiguous: types " + matchedClass.getName() + " and "
                            + methodClass.getName() + " match " + paramClass.getName());
                }
            }
        }
        return matchedMethod;
    }

    private String condenseText(final String text) {
        if (text.length() <= MAX_REPORT_NESTED_TEXT) {
            return text;
        }
        int ends = (MAX_REPORT_NESTED_TEXT - ELLIPSIS.length()) / 2;
        return new StringBuffer(text).replace(ends, text.length() - ends, ELLIPSIS).toString();
    }


    private class MethodAndObject {
        private Method method;
        private Object object;
        public MethodAndObject(Method method, Object object) {
            this.method = method;
            this.object = object;
        }
    }

    /**
     *
     */
    private AntTypeDefinition findRestrictedDefinition(
        ComponentHelper helper, String componentName, List methods) {
        AntTypeDefinition definition = null;
        Class matchedDefinitionClass = null;

        List definitions = helper.getRestrictedDefinitions(componentName);
        if (definitions == null) {
            return null;
        }
        for (int i = 0; i < definitions.size(); ++i) {
            AntTypeDefinition d = (AntTypeDefinition) definitions.get(i);
            Class exposedClass = d.getExposedClass(helper.getProject());
            if (exposedClass == null) {
                continue;
            }
            Method method  = findMatchingMethod(exposedClass, methods);
            if (method == null) {
                continue;
            }
            if (matchedDefinitionClass != null) {
                throw new BuildException(
                    "ambiguous: restricted definitions for "
                    + componentName + " "
                    + matchedDefinitionClass + " and " + exposedClass);
            }
            matchedDefinitionClass = exposedClass;
            definition = d;
        }
        return definition;
    }

    private MethodAndObject createRestricted(
        ComponentHelper helper, String elementName, List addTypeMethods) {

        Project project = helper.getProject();

        AntTypeDefinition restrictedDefinition =
            findRestrictedDefinition(helper, elementName, addTypeMethods);

        if (restrictedDefinition == null) {
            return null;
        }

        Method addMethod = findMatchingMethod(
            restrictedDefinition.getExposedClass(project), addTypeMethods);
        if (addMethod == null) {
            throw new BuildException(
                "Ant Internal Error - contract mismatch for "
                + elementName);
        }
        Object addedObject = restrictedDefinition.create(project);
        if (addedObject == null) {
            throw new BuildException(
                "Failed to create object " + elementName
                + " of type " + restrictedDefinition.getTypeClass(project));
        }
        return new MethodAndObject(addMethod, addedObject);
    }

    private MethodAndObject createTopLevel(
        ComponentHelper helper, String elementName, List methods) {
        Class clazz = helper.getComponentClass(elementName);
        if (clazz == null) {
            return null;
        }
        Method addMethod = findMatchingMethod(clazz, addTypeMethods);
        if (addMethod == null) {
            return null;
        }
        Object addedObject = helper.createComponent(elementName);
        return new MethodAndObject(addMethod, addedObject);
    }

}