Java tutorial
/* * 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.lang.reflect; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import org.apache.commons.lang.ArrayUtils; import org.apache.commons.lang.ClassUtils; /** * <p> Utility reflection methods focused on methods, originally from Commons BeanUtils. * Differences from the BeanUtils version may be noted, especially where similar functionality * already existed within Lang. * </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 on JREs prior to 1.4. * 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 privileges. * If this call fails then the method may fail.</p> * * @author Apache Software Foundation * @author Craig R. McClanahan * @author Ralph Schaer * @author Chris Audley * @author Rey François * @author Gregor Raýman * @author Jan Sorensen * @author Robert Burrell Donkin * @author Matt Benson * @since 2.5 * @version $Id: MethodUtils.java 911986 2010-02-19 21:19:05Z niallp $ */ public class MethodUtils { /** * <p>MethodUtils instances should NOT be constructed in standard programming. * Instead, the class should be used as * <code>MethodUtils.getAccessibleMethod(method)</code>.</p> * * <p>This constructor is public to permit tools that require a JavaBean * instance to operate.</p> */ public MethodUtils() { super(); } /** * <p>Invoke a named method whose parameter type matches the object type.</p> * * <p>This method delegates the method search to {@link #getMatchingAccessibleMethod(Class, String, Class[])}.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> object * 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 { return invokeMethod(object, methodName, new Object[] { arg }); } /** * <p>Invoke a named method whose parameter type matches the object type.</p> * * <p>This method delegates the method search to {@link #getMatchingAccessibleMethod(Class, String, Class[])}.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> object * 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 = ArrayUtils.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>This method delegates the method search to {@link #getMatchingAccessibleMethod(Class, String, Class[])}.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> object * 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 = ArrayUtils.EMPTY_CLASS_ARRAY; } if (args == null) { args = ArrayUtils.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 { return invokeExactMethod(object, methodName, new Object[] { arg }); } /** * <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 = ArrayUtils.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); } /** * <p>Invoke a method whose parameter types match exactly the parameter * types given.</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 * @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 invokeExactMethod(Object object, String methodName, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = ArrayUtils.EMPTY_OBJECT_ARRAY; } if (parameterTypes == null) { parameterTypes = ArrayUtils.EMPTY_CLASS_ARRAY; } Method method = getAccessibleMethod(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 static method whose parameter types match exactly the parameter * types given.</p> * * <p>This uses reflection to invoke the method obtained from a call to * {@link #getAccessibleMethod(Class, String, Class[])}.</p> * * @param cls invoke static method on this class * @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 invokeExactStaticMethod(Class cls, String methodName, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = ArrayUtils.EMPTY_OBJECT_ARRAY; } if (parameterTypes == null) { parameterTypes = ArrayUtils.EMPTY_CLASS_ARRAY; } Method method = getAccessibleMethod(cls, methodName, parameterTypes); if (method == null) { throw new NoSuchMethodException( "No such accessible method: " + methodName + "() on class: " + cls.getName()); } return method.invoke(null, args); } /** * <p>Invoke a named static method whose parameter type matches the object type.</p> * * <p>This method delegates the method search to {@link #getMatchingAccessibleMethod(Class, String, Class[])}.</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 #invokeStaticMethod(Class objectClass,String methodName,Object [] args)}. * </p> * * @param cls invoke static method on this class * @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 invokeStaticMethod(Class cls, String methodName, Object arg) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { return invokeStaticMethod(cls, methodName, new Object[] { arg }); } /** * <p>Invoke a named static method whose parameter type matches the object type.</p> * * <p>This method delegates the method search to {@link #getMatchingAccessibleMethod(Class, String, Class[])}.</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 #invokeStaticMethod(Class objectClass,String methodName,Object [] args,Class[] parameterTypes)}. * </p> * * @param cls invoke static method on this class * @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 invokeStaticMethod(Class cls, String methodName, Object[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = ArrayUtils.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 invokeStaticMethod(cls, methodName, args, parameterTypes); } /** * <p>Invoke a named static method whose parameter type matches the object type.</p> * * <p>This method delegates the method search to {@link #getMatchingAccessibleMethod(Class, String, Class[])}.</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 cls invoke static method on this class * @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 invokeStaticMethod(Class cls, String methodName, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (parameterTypes == null) { parameterTypes = ArrayUtils.EMPTY_CLASS_ARRAY; } if (args == null) { args = ArrayUtils.EMPTY_OBJECT_ARRAY; } Method method = getMatchingAccessibleMethod(cls, methodName, parameterTypes); if (method == null) { throw new NoSuchMethodException( "No such accessible method: " + methodName + "() on class: " + cls.getName()); } return method.invoke(null, args); } /** * <p>Invoke a static method whose parameter type matches exactly the object * type.</p> * * <p> This is a convenient wrapper for * {@link #invokeExactStaticMethod(Class objectClass,String methodName,Object [] args)}. * </p> * * @param cls invoke static method on this class * @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 invokeExactStaticMethod(Class cls, String methodName, Object arg) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { return invokeExactStaticMethod(cls, methodName, new Object[] { arg }); } /** * <p>Invoke a static method whose parameter types match exactly the object * types.</p> * * <p> This uses reflection to invoke the method obtained from a call to * {@link #getAccessibleMethod(Class, String, Class[])}.</p> * * @param cls invoke static method on this class * @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 invokeExactStaticMethod(Class cls, String methodName, Object[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = ArrayUtils.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 invokeExactStaticMethod(cls, methodName, args, parameterTypes); } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) with given name and a single parameter. If no such method * can be found, return <code>null</code>. * Basically, a convenience wrapper that constructs a <code>Class</code> * array for you.</p> * * @param cls get method from this class * @param methodName get method with this name * @param parameterType taking this type of parameter * @return The accessible method */ public static Method getAccessibleMethod(Class cls, String methodName, Class parameterType) { return getAccessibleMethod(cls, methodName, new Class[] { parameterType }); } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) with given name and parameters. If no such method * can be found, return <code>null</code>. * This is just a convenient wrapper for * {@link #getAccessibleMethod(Method method)}.</p> * * @param cls get method from this class * @param methodName get method with this name * @param parameterTypes with these parameters types * @return The accessible method */ public static Method getAccessibleMethod(Class cls, String methodName, Class[] parameterTypes) { try { return getAccessibleMethod(cls.getMethod(methodName, parameterTypes)); } catch (NoSuchMethodException e) { return (null); } } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) that implements the specified Method. If no such method * can be found, return <code>null</code>.</p> * * @param method The method that we wish to call * @return The accessible method */ public static Method getAccessibleMethod(Method method) { if (!MemberUtils.isAccessible(method)) { return null; } // If the declaring class is public, we are done Class cls = method.getDeclaringClass(); if (Modifier.isPublic(cls.getModifiers())) { return method; } String methodName = method.getName(); Class[] parameterTypes = method.getParameterTypes(); // Check the implemented interfaces and subinterfaces method = getAccessibleMethodFromInterfaceNest(cls, methodName, parameterTypes); // Check the superclass chain if (method == null) { method = getAccessibleMethodFromSuperclass(cls, methodName, parameterTypes); } return method; } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) by scanning through the superclasses. If no such method * can be found, return <code>null</code>.</p> * * @param cls Class to be checked * @param methodName Method name of the method we wish to call * @param parameterTypes The parameter type signatures * @return the accessible method or <code>null</code> if not found */ private static Method getAccessibleMethodFromSuperclass(Class cls, String methodName, Class[] parameterTypes) { Class parentClass = cls.getSuperclass(); while (parentClass != null) { if (Modifier.isPublic(parentClass.getModifiers())) { try { return parentClass.getMethod(methodName, parameterTypes); } catch (NoSuchMethodException e) { return null; } } parentClass = parentClass.getSuperclass(); } return null; } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) that implements the specified method, by scanning through * all implemented interfaces and subinterfaces. If no such method * can be found, return <code>null</code>.</p> * * <p> There isn't any good reason why this method must be private. * It is because there doesn't seem any reason why other classes should * call this rather than the higher level methods.</p> * * @param cls Parent class for the interfaces to be checked * @param methodName Method name of the method we wish to call * @param parameterTypes The parameter type signatures * @return the accessible method or <code>null</code> if not found */ private static Method getAccessibleMethodFromInterfaceNest(Class cls, String methodName, Class[] parameterTypes) { Method method = null; // Search up the superclass chain for (; cls != null; cls = cls.getSuperclass()) { // Check the implemented interfaces of the parent class Class[] interfaces = cls.getInterfaces(); for (int i = 0; i < interfaces.length; i++) { // Is this interface public? if (!Modifier.isPublic(interfaces[i].getModifiers())) { continue; } // Does the method exist on this interface? try { method = interfaces[i].getDeclaredMethod(methodName, parameterTypes); } catch (NoSuchMethodException e) { /* * Swallow, if no method is found after the loop then this * method returns null. */ } if (method != null) { break; } // Recursively check our parent interfaces method = getAccessibleMethodFromInterfaceNest(interfaces[i], methodName, parameterTypes); if (method != null) { break; } } } return method; } /** * <p>Find an accessible method that matches the given name and has compatible parameters. * Compatible parameters mean that every method parameter is assignable from * the given parameters. * In other words, it finds a method with the given name * that will take the parameters given.<p> * * <p>This method is used by * {@link * #invokeMethod(Object object, String methodName, Object[] args, Class[] parameterTypes)}. * * <p>This method can match primitive parameter by passing in wrapper classes. * For example, a <code>Boolean</code> will match a primitive <code>boolean</code> * parameter. * * @param cls find method in this class * @param methodName find method with this name * @param parameterTypes find method with most compatible parameters * @return The accessible method */ public static Method getMatchingAccessibleMethod(Class cls, String methodName, Class[] parameterTypes) { try { Method method = cls.getMethod(methodName, parameterTypes); MemberUtils.setAccessibleWorkaround(method); return method; } catch (NoSuchMethodException e) { /* SWALLOW */ } // search through all methods Method bestMatch = null; Method[] methods = cls.getMethods(); for (int i = 0, size = methods.length; i < size; i++) { if (methods[i].getName().equals(methodName)) { // compare parameters if (ClassUtils.isAssignable(parameterTypes, methods[i].getParameterTypes(), true)) { // get accessible version of method Method accessibleMethod = getAccessibleMethod(methods[i]); if (accessibleMethod != null) { if (bestMatch == null || MemberUtils.compareParameterTypes(accessibleMethod.getParameterTypes(), bestMatch.getParameterTypes(), parameterTypes) < 0) { bestMatch = accessibleMethod; } } } } } if (bestMatch != null) { MemberUtils.setAccessibleWorkaround(bestMatch); } return bestMatch; } }