helper classes for reflection

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@481956 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/util/ReflectUtil.java

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+/*
+ *  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.util;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import org.apache.tools.ant.BuildException;
+import java.lang.reflect.Field;
+
+/**
+ * Utility class to handle reflection on java objects.
+ * The class contains static methods to call reflection
+ * methods, catch any exceptions, converting them
+ * to BuildExceptions.
+ */
+
+public class ReflectUtil {
+
+    /**  private constructor */
+    private ReflectUtil() {
+    }
+
+    /**
+     * Call a method on the object with no parameters.
+     * @param obj  the object to invoke the method on.
+     * @param methodName the name of the method to call
+     * @return the object returned by the method
+     */
+    public static Object invoke(Object obj, String methodName) {
+        try {
+            Method method;
+            method = obj.getClass().getMethod(
+                methodName, (Class[]) null);
+            return method.invoke(obj, (Object[]) null);
+        } catch (Exception t) {
+            throwBuildException(t);
+            return null; // NotReached
+        }
+    }
+
+    /**
+     * Call a method on the object with one argument.
+     * @param obj  the object to invoke the method on.
+     * @param methodName the name of the method to call
+     * @param argType    the type of argument.
+     * @param arg        the value of the argument.
+     * @return the object returned by the method
+     */
+    public static Object invoke(
+        Object obj, String methodName, Class argType, Object arg) {
+        try {
+            Method method;
+            method = obj.getClass().getMethod(
+                methodName, new Class[] {argType});
+            return method.invoke(obj, new Object[] {arg});
+        } catch (Exception t) {
+            throwBuildException(t);
+            return null; // NotReached
+        }
+    }
+
+    /**
+     * Call a method on the object with two argument.
+     * @param obj  the object to invoke the method on.
+     * @param methodName the name of the method to call
+     * @param argType1   the type of the first argument.
+     * @param arg1       the value of the first argument.
+     * @param argType2   the type of the second argument.
+     * @param arg2       the value of the second argument.
+     * @return the object returned by the method
+     */
+    public static Object invoke(
+        Object obj, String methodName, Class argType1, Object arg1,
+        Class argType2, Object arg2) {
+        try {
+            Method method;
+            method = obj.getClass().getMethod(
+                methodName, new Class[] {argType1, argType2});
+            return method.invoke(obj, new Object[] {arg1, arg2});
+        } catch (Exception t) {
+            throwBuildException(t);
+            return null; // NotReached
+        }
+    }
+
+    /**
+     * Get the value of a field in an object.
+     * @param obj the object to look at.
+     * @param fieldName the name of the field in the object.
+     * @return the value of the field.
+     * @throws BuildException if there is an error.
+     */
+    public static Object getField(Object obj, String fieldName)
+        throws BuildException {
+        try {
+            Field field = obj.getClass().getDeclaredField(fieldName);
+            field.setAccessible(true);
+            return field.get(obj);
+        } catch (Exception t) {
+            throwBuildException(t);
+            return null; // NotReached
+        }
+    }
+
+    /**
+     * A method to convert an invocationTargetException to
+     * a buildexception and throw it.
+     * @param t the invocation target exception.
+     * @throws BuildException the converted exception.
+     */
+    public static void throwBuildException(Exception t)
+        throws BuildException {
+        if (t instanceof InvocationTargetException) {
+            Throwable t2 = ((InvocationTargetException) t)
+                .getTargetException();
+            if (t2 instanceof BuildException) {
+                throw (BuildException) t2;
+            }
+            throw new BuildException(t2);
+        } else {
+            throw new BuildException(t);
+        }
+    }
+}

src/main/org/apache/tools/ant/util/ReflectWrapper.java

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+/*
+ *  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.util;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import org.apache.tools.ant.BuildException;
+import java.lang.reflect.Field;
+
+/**
+ * Utility class to handle reflection on java objects.
+ * The class is a holder class for an object and
+ * uses java reflection to call methods on the objects.
+ * If things go wrong, BuildExceptions are thrown.
+ */
+
+public class ReflectWrapper {
+    private Object obj;
+    /**
+     * Construct a wrapped object using the no arg constructor.
+     * @param loader the classloader to use to construct the class.
+     * @param name the classname of the object to construct.
+     */
+    public ReflectWrapper(ClassLoader loader, String name) {
+        try {
+            Class clazz;
+            clazz = Class.forName(name, true, loader);
+            Constructor constructor;
+            constructor = clazz.getConstructor((Class[]) null);
+            obj = constructor.newInstance((Object[]) null);
+        } catch (Exception t) {
+            ReflectUtil.throwBuildException(t);
+        }
+    }
+
+    /**
+     * Constructor using a passed in object.
+     * @param obj the object to wrap.
+     */
+    public ReflectWrapper(Object obj) {
+        this.obj = obj;
+    }
+
+    /**
+     * @return the wrapped object.
+     */
+    public Object getObject() {
+        return obj;
+    }
+
+    /**
+     * Call a method on the object with no parameters.
+     * @param methodName the name of the method to call
+     * @return the object returned by the method
+     */
+    public Object invoke(String methodName) {
+        return ReflectUtil.invoke(obj, methodName);
+    }
+
+    /**
+     * Call a method on the object with one argument.
+     * @param methodName the name of the method to call
+     * @param argType    the type of argument.
+     * @param arg        the value of the argument.
+     * @return the object returned by the method
+     */
+    public Object invoke(
+        String methodName, Class argType, Object arg) {
+        return ReflectUtil.invoke(obj, methodName, argType, arg);
+    }
+
+    /**
+     * Call a method on the object with one argument.
+     * @param methodName the name of the method to call
+     * @param argType1   the type of the first argument.
+     * @param arg1       the value of the first argument.
+     * @param argType2   the type of the second argument.
+     * @param arg2       the value of the second argument.
+     * @return the object returned by the method
+     */
+    public Object invoke(
+        String methodName, Class argType1, Object arg1,
+        Class argType2, Object arg2) {
+        return ReflectUtil.invoke(
+            obj, methodName, argType1, arg1, argType2, arg2);
+    }
+}