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

/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000-2002 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Ant", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.apache.tools.ant;

import org.apache.tools.ant.types.Path;
import org.apache.tools.ant.types.EnumeratedAttribute;

import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Constructor;
import java.io.File;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Locale;

/**
 * Helper class that collects the methods a task or nested element
 * holds to set attributes, create nested elements or hold PCDATA
 * elements.
 *
 * @author <a href="mailto:stefan.bodewig@epost.de">Stefan Bodewig</a>
 */
public class IntrospectionHelper implements BuildListener {

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

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

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

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

    /**
     * Map from attribute names to methods to store configured nested types 
     * (String to NestedStorer).
     */
    private Hashtable nestedStorers;

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

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

    /**
     * Helper instances we've already created (Class to IntrospectionHelper).
     */
    private static Hashtable 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 Hashtable PRIMITIVE_TYPE_MAP = new Hashtable(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]);
        }
    }

    // XXX: (Jon Skeet) The documentation below doesn't draw a clear 
    // distinction between addConfigured and add. It's obvious what the
    // code *here* does (addConfigured sets both a creator method which
    // calls a no-arg constructor and a storer method which calls the
    // method we're looking at, whlie add just sets a creator method
    // which calls the method we're looking at) but it's not at all
    // obvious what the difference in actual *effect* will be later
    // on. I can't see any mention of addConfiguredXXX in "Developing
    // with Ant" (at least in the version on the web site). Someone
    // who understands should update this documentation 
    // (and preferably the manual too) at some stage.
    /**
     * 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>foobar</code> 
     * and of type <code>Baz</code>, so long as
     * <code>Baz</code> is not an array, primitive or String type. 
     * <code>Baz</code> must have an accessible constructor taking no 
     * arguments.
     * </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) {
        attributeTypes = new Hashtable();
        attributeSetters = new Hashtable();
        nestedTypes = new Hashtable();
        nestedCreators = new Hashtable();
        nestedStorers = new Hashtable();

        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();

            // not really user settable properties on tasks
            if (org.apache.tools.ant.Task.class.isAssignableFrom(bean)
                 && args.length == 1 && isHiddenSetMethod(name, args[0])) {
                continue;
            }

            // hide addTask for TaskContainers
            if (org.apache.tools.ant.TaskContainer.class.isAssignableFrom(bean)
                && 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]);
                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");
                nestedTypes.put(propName, returnType);
                nestedCreators.put(propName, new NestedCreator() {

                        public Object create(Object parent)
                            throws InvocationTargetException,
                            IllegalAccessException {

                            return m.invoke(parent, new Object[] {});
                        }

                    });
                nestedStorers.remove(propName);

            } 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 {
                    final Constructor c =
                        args[0].getConstructor(new Class[] {});
                    String propName = getPropertyName(name, "addConfigured");
                    nestedTypes.put(propName, args[0]);
                    nestedCreators.put(propName, new NestedCreator() {

                            public Object create(Object parent)
                                throws InvocationTargetException, IllegalAccessException, InstantiationException {

                                Object o = c.newInstance(new Object[] {});
                                return o;
                            }

                        });
                    nestedStorers.put(propName, new NestedStorer() {

                            public void store(Object parent, Object child)
                                throws InvocationTargetException, IllegalAccessException, InstantiationException {

                                m.invoke(parent, new Object[] {child});
                            }

                        });
                } catch (NoSuchMethodException nse) {
                }
            } 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 {
                    final Constructor c =
                        args[0].getConstructor(new Class[] {});
                    String propName = getPropertyName(name, "add");
                    nestedTypes.put(propName, args[0]);
                    nestedCreators.put(propName, new NestedCreator() {

                            public Object create(Object parent)
                                throws InvocationTargetException, IllegalAccessException, InstantiationException {

                                Object o = c.newInstance(new Object[] {});
                                m.invoke(parent, new Object[] {o});
                                return o;
                            }

                        });
                    nestedStorers.remove(name);
                } catch (NoSuchMethodException nse) {
                }
            }
        }
    }

    /** 
     * 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) {
        IntrospectionHelper ih = (IntrospectionHelper) helpers.get(c);
        if (ih == null) {
            ih = new IntrospectionHelper(c);
            helpers.put(c, 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 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 {
        AttributeSetter as 
            = (AttributeSetter) attributeSetters.get(attributeName);
        if (as == null) {
            String msg = p.getElementName(element) +
            //String msg = "Class " + element.getClass().getName() +
                " doesn't support the \"" + attributeName + "\" attribute.";
            throw new BuildException(msg);
        }
        try {
            as.set(p, element, value);
        } catch (IllegalAccessException ie) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ie);
        } catch (InvocationTargetException ite) {
            Throwable t = ite.getTargetException();
            if (t instanceof BuildException) {
                throw (BuildException) t;
            }
            throw new BuildException(t);
        }
    }

    /**
     * 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) {
            // Element doesn't handle text content
            if (text.trim().length() == 0) {
                // Only whitespace - ignore
                return;
            } else {
                // Not whitespace - fail
                String msg = project.getElementName(element) +
                    " doesn't support nested text data.";
                throw new BuildException(msg);
            }
        }
        try {
            addText.invoke(element, new String[] {text});
        } catch (IllegalAccessException ie) {
            // impossible as getMethods should only return public methods
            throw new BuildException(ie);
        } catch (InvocationTargetException ite) {
            Throwable t = ite.getTargetException();
            if (t instanceof BuildException) {
                throw (BuildException) t;
            }
            throw new BuildException(t);
        }
    }

    /**
     * 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
     * 
     * @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 = (NestedCreator) nestedCreators.get(elementName);
        if (nc == null) {
            String msg = project.getElementName(parent) +
                " doesn't support the nested \"" + elementName + "\" element.";
            throw new BuildException(msg);
        }
        try {
            Object nestedElement = nc.create(parent);
            if (nestedElement instanceof ProjectComponent) {
                ((ProjectComponent) nestedElement).setProject(project);
            }
            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) {
            Throwable t = ite.getTargetException();
            if (t instanceof BuildException) {
                throw (BuildException) t;
            }
            throw new BuildException(t);
        }
    }

    /**
     * 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;
        }
        NestedStorer ns = (NestedStorer) nestedStorers.get(elementName);
        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) {
            Throwable t = ite.getTargetException();
            if (t instanceof BuildException) {
                throw (BuildException) t;
            }
            throw 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) {
            String msg = "Class " + bean.getName() +
                " doesn't support the nested \"" + elementName + "\" element.";
            throw new BuildException(msg);
        }
        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) {
            String msg = "Class " + bean.getName() +
                " doesn't support the \"" + attributeName + "\" attribute.";
            throw new BuildException(msg);
        }
        return at;
    }

    /**
     * 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.
     */
    public Enumeration getAttributes() {
        return attributeSetters.keys();
    }

    /**
     * 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.
     */
    public Enumeration getNestedElements() {
        return nestedTypes.keys();
    }

    /**
     * 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>.
     * 
     * @return an appropriate AttributeSetter instance, or <code>null</code>
     *         if no appropriate conversion is available.
     */
    private AttributeSetter createAttributeSetter(final Method m,
                                                  Class arg) {
        // 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() {
                    public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                        m.invoke(parent, new String[] {value});
                    }
                };

        // char and Character get special treatment - take the first character
        } else if (java.lang.Character.class.equals(reflectedArg)) {
            return new AttributeSetter() {
                    public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                        m.invoke(parent, new Character[] {new Character(value.charAt(0))});
                    }

                };
        // boolean and Boolean get special treatment because we 
        // have a nice method in Project
        } else if (java.lang.Boolean.class.equals(reflectedArg)) {
            return new AttributeSetter() {
                    public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                        m.invoke(parent,
                                 new Boolean[] {new Boolean(Project.toBoolean(value))});
                    }

                };

        // Class doesn't have a String constructor but a decent factory method
        } else if (java.lang.Class.class.equals(reflectedArg)) {
            return new AttributeSetter() {
                    public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException, BuildException {
                        try {
                            m.invoke(parent, new Class[] {Class.forName(value)});
                        } catch (ClassNotFoundException ce) {
                            throw new BuildException(ce);
                        }
                    }
                };

        // resolve relative paths through Project
        } else if (java.io.File.class.equals(reflectedArg)) {
            return new AttributeSetter() {
                    public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                        m.invoke(parent, new File[] {p.resolveFile(value)});
                    }

                };

        // resolve relative paths through Project
        } else if (org.apache.tools.ant.types.Path.class.equals(reflectedArg)) {
            return new AttributeSetter() {
                    public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException {
                        m.invoke(parent, new Path[] {new Path(p, value)});
                    }

                };

        // EnumeratedAttributes have their own helper class
        } else if (org.apache.tools.ant.types.EnumeratedAttribute.class.isAssignableFrom(reflectedArg)) {
            return new AttributeSetter() {
                    public void set(Project p, Object parent, String value)
                        throws InvocationTargetException, IllegalAccessException, BuildException {
                        try {
                            org.apache.tools.ant.types.EnumeratedAttribute ea = 
                                (org.apache.tools.ant.types.EnumeratedAttribute) reflectedArg.newInstance();
                            ea.setValue(value);
                            m.invoke(parent, new EnumeratedAttribute[] {ea});
                        } catch (InstantiationException ie) {
                            throw new BuildException(ie);
                        }
                    }
                };

        // worst case. look for a public String constructor and use it
        // This is used (deliberately) for all primitives/wrappers other than 
        // char and boolean
        } else {

            try {
                final Constructor c =
                    reflectedArg.getConstructor(new Class[] {java.lang.String.class});

                return new AttributeSetter() {
                        public void set(Project p, Object parent,
                                        String value)
                            throws InvocationTargetException, IllegalAccessException, BuildException {
                            try {
                                Object attribute = c.newInstance(new String[] {value});
                                if (attribute instanceof ProjectComponent) {
                                    ((ProjectComponent) attribute).setProject(p);
                                }
                                m.invoke(parent, new Object[] {attribute});
                            } catch (InstantiationException ie) {
                                throw new BuildException(ie);
                            }
                        }
                    };

            } catch (NoSuchMethodException nme) {
            }
        }

        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
     */
    protected 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 String getPropertyName(String methodName, String prefix) {
        int start = prefix.length();
        return methodName.substring(start).toLowerCase(Locale.US);
    }

    /**
     * Internal interface used to create nested elements. Not documented 
     * in detail for reasons of source code readability.
     */
    private interface NestedCreator {
        Object create(Object parent)
            throws InvocationTargetException, IllegalAccessException, InstantiationException;
    }

    /**
     * Internal interface used to storing nested elements. Not documented 
     * in detail for reasons of source code readability.
     */
    private interface NestedStorer {
        void store(Object parent, Object child)
            throws InvocationTargetException, IllegalAccessException, InstantiationException;
    }

    /**
     * Internal interface used to setting element attributes. Not documented 
     * in detail for reasons of source code readability.
     */
    private interface AttributeSetter {
        void set(Project p, Object parent, String value)
            throws InvocationTargetException, IllegalAccessException,
                   BuildException;
    }

    /**
     * Clears all storage used by this class, including the static cache of 
     * helpers.
     * 
     * @param event Ignored in this implementation.
     */
    public void buildFinished(BuildEvent event) {
        attributeTypes.clear();
        attributeSetters.clear();
        nestedTypes.clear();
        nestedCreators.clear();
        addText = null;
        helpers.clear();
    }

    /** Empty implementation to satisfy the BuildListener interface. */
    public void buildStarted(BuildEvent event) {}
    /** Empty implementation to satisfy the BuildListener interface. */
    public void targetStarted(BuildEvent event) {}
    /** Empty implementation to satisfy the BuildListener interface. */
    public void targetFinished(BuildEvent event) {}
    /** Empty implementation to satisfy the BuildListener interface. */
    public void taskStarted(BuildEvent event) {}
    /** Empty implementation to satisfy the BuildListener interface. */
    public void taskFinished(BuildEvent event) {}
    /** Empty implementation to satisfy the BuildListener interface. */
    public void messageLogged(BuildEvent event) {}
}