methodutils.java

APACHE 公司出的java bean 工具包

/*
 * 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.commons.beanutils;


import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

import java.util.WeakHashMap;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;


/**
 * <p> Utility reflection methods focussed on methods in general rather than properties in particular. </p>
 *
 * <h3>Known Limitations</h3>
 * <h4>Accessing Public Methods In A Default Access Superclass</h4>
 * <p>There is an issue when invoking public methods contained in a default access superclass.
 * Reflection locates these methods fine and correctly assigns them as public.
 * However, an <code>IllegalAccessException</code> is thrown if the method is invoked.</p>
 *
 * <p><code>MethodUtils</code> contains a workaround for this situation. 
 * It will attempt to call <code>setAccessible</code> on this method.
 * If this call succeeds, then the method can be invoked as normal.
 * This call will only succeed when the application has sufficient security privilages. 
 * If this call fails then a warning will be logged and the method may fail.</p>
 *
 * @author Craig R. McClanahan
 * @author Ralph Schaer
 * @author Chris Audley
 * @author Rey Fran&#231;ois
 * @author Gregor Ra&#253;man
 * @author Jan Sorensen
 * @author Robert Burrell Donkin
 */

public class MethodUtils {

    // --------------------------------------------------------- Private Methods
    
    /** 
     * Only log warning about accessibility work around once.
     * <p>
     * Note that this is broken when this class is deployed via a shared
     * classloader in a container, as the warning message will be emitted
     * only once, not once per webapp. However making the warning appear
     * once per webapp means having a map keyed by context classloader
     * which introduces nasty memory-leak problems. As this warning is
     * really optional we can ignore this problem; only one of the webapps
     * will get the warning in its logs but that should be good enough.
     */
    private static boolean loggedAccessibleWarning = false;

    /** An empty class array */
    private static final Class[] EMPTY_CLASS_PARAMETERS = new Class[0];
    /** An empty object array */
    private static final Object[] EMPTY_OBJECT_ARRAY = new Object[0];

    /**
     * Stores a cache of MethodDescriptor -> Method in a WeakHashMap.
     * <p>
     * The keys into this map only ever exist as temporary variables within
     * methods of this class, and are never exposed to users of this class.
     * This means that the WeakHashMap is used only as a mechanism for 
     * limiting the size of the cache, ie a way to tell the garbage collector
     * that the contents of the cache can be completely garbage-collected 
     * whenever it needs the memory. Whether this is a good approach to
     * this problem is doubtful; something like the commons-collections
     * LRUMap may be more appropriate (though of course selecting an
     * appropriate size is an issue).
     * <p>
     * This static variable is safe even when this code is deployed via a
     * shared classloader because it is keyed via a MethodDescriptor object
     * which has a Class as one of its members and that member is used in
     * the MethodDescriptor.equals method. So two components that load the same
     * class via different classloaders will generate non-equal MethodDescriptor
     * objects and hence end up with different entries in the map.
     */
    private static WeakHashMap cache = new WeakHashMap();
    
    // --------------------------------------------------------- Public Methods
    
    /**
     * <p>Invoke a named method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than <code>invokeExactMethod()</code>.
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeMethod(Object object,String methodName,Object [] args)}.
     * </p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param arg use this argument
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeMethod(
            Object object,
            String methodName,
            Object arg)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {

        Object[] args = {arg};
        return invokeMethod(object, methodName, args);

    }


    /**
     * <p>Invoke a named method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than {@link #invokeExactMethod(Object object,String methodName,Object [] args)}. 
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}.
     * </p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeMethod(
            Object object,
            String methodName,
            Object[] args)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
        int arguments = args.length;
        Class[] parameterTypes = new Class[arguments];
        for (int i = 0; i < arguments; i++) {
            parameterTypes[i] = args[i].getClass();
        }
        return invokeMethod(object, methodName, args, parameterTypes);

    }


    /**
     * <p>Invoke a named method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than {@link 
     * #invokeExactMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}. 
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @param parameterTypes match these parameters - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeMethod(
            Object object,
            String methodName,
            Object[] args,
            Class[] parameterTypes)
                throws
                    NoSuchMethodException,
                    IllegalAccessException,
                    InvocationTargetException {
                    
        if (parameterTypes == null) {
            parameterTypes = EMPTY_CLASS_PARAMETERS;
        }        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  

        Method method = getMatchingAccessibleMethod(
                object.getClass(),
                methodName,
                parameterTypes);
        if (method == null) {
            throw new NoSuchMethodException("No such accessible method: " +
                    methodName + "() on object: " + object.getClass().getName());
        }
        return method.invoke(object, args);
    }


    /**
     * <p>Invoke a method whose parameter type matches exactly the object
     * type.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeExactMethod(Object object,String methodName,Object [] args)}.
     * </p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param arg use this argument
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeExactMethod(
            Object object,
            String methodName,
            Object arg)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {

        Object[] args = {arg};
        return invokeExactMethod(object, methodName, args);

    }


    /**
     * <p>Invoke a method whose parameter types match exactly the object
     * types.</p>
     *
     * <p> This uses reflection to invoke the method obtained from a call to
     * <code>getAccessibleMethod()</code>.</p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeExactMethod(
            Object object,
            String methodName,
            Object[] args)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
        int arguments = args.length;
        Class[] parameterTypes = new Class[arguments];
        for (int i = 0; i < arguments; i++) {
            parameterTypes[i] = args[i].getClass();
        }
        return invokeExactMethod(object, methodName, args, parameterTypes);