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.lang3.reflect; import java.lang.annotation.Annotation; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.lang.reflect.Type; import java.lang.reflect.TypeVariable; import java.util.Arrays; import java.util.ArrayList; import java.util.Iterator; import java.util.LinkedHashSet; import java.util.List; import java.util.Map; import java.util.Set; import org.apache.commons.lang3.ArrayUtils; import org.apache.commons.lang3.ClassUtils; import org.apache.commons.lang3.ClassUtils.Interfaces; import org.apache.commons.lang3.Validate; /** * <p>Utility reflection methods focused on {@link Method}s, 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 {@code public} methods contained in a default access superclass on JREs prior to 1.4. * Reflection locates these methods fine and correctly assigns them as {@code public}. * However, an {@link IllegalAccessException} is thrown if the method is invoked.</p> * * <p>{@link MethodUtils} contains a workaround for this situation. * It will attempt to call {@link java.lang.reflect.AccessibleObject#setAccessible(boolean)} 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> * * @since 2.5 * @version $Id$ */ public class MethodUtils { /** * <p>{@link MethodUtils} instances should NOT be constructed in standard programming. * Instead, the class should be used as * {@code MethodUtils.getAccessibleMethod(method)}.</p> * * <p>This constructor is {@code public} to permit tools that require a JavaBean * instance to operate.</p> */ public MethodUtils() { super(); } /** * <p>Invokes a named method without parameters.</p> * * <p>This method delegates the method search to {@link #getMatchingAccessibleMethod(Class, String, Class[])}.</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 * @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 * * @since 3.4 */ public static Object invokeMethod(final Object object, final String methodName) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { return invokeMethod(object, methodName, ArrayUtils.EMPTY_OBJECT_ARRAY, null); } /** * <p>Invokes 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} object * would match a {@code boolean} 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(final Object object, final String methodName, Object... args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { args = ArrayUtils.nullToEmpty(args); final Class<?>[] parameterTypes = ClassUtils.toClass(args); return invokeMethod(object, methodName, args, parameterTypes); } /** * <p>Invokes 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} object * would match a {@code boolean} 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(final Object object, final String methodName, Object[] args, Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { parameterTypes = ArrayUtils.nullToEmpty(parameterTypes); args = ArrayUtils.nullToEmpty(args); final 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>Invokes a 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 object invoke method on this object * @param methodName get method with this name * @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 * * @since 3.4 */ public static Object invokeExactMethod(final Object object, final String methodName) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { return invokeExactMethod(object, methodName, ArrayUtils.EMPTY_OBJECT_ARRAY, null); } /** * <p>Invokes a method with no parameters.</p> * * <p>This uses reflection to invoke the method obtained from a call to * {@link #getAccessibleMethod}(Class,String,Class[])}.</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(final Object object, final String methodName, Object... args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { args = ArrayUtils.nullToEmpty(args); final Class<?>[] parameterTypes = ClassUtils.toClass(args); return invokeExactMethod(object, methodName, args, parameterTypes); } /** * <p>Invokes 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 * {@link #getAccessibleMethod(Class,String,Class[])}.</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 {@code 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(final Object object, final String methodName, Object[] args, Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { args = ArrayUtils.nullToEmpty(args); parameterTypes = ArrayUtils.nullToEmpty(parameterTypes); final 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>Invokes a {@code 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 {@code null} as empty array * @param parameterTypes match these parameters - treat {@code 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(final Class<?> cls, final String methodName, Object[] args, Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { args = ArrayUtils.nullToEmpty(args); parameterTypes = ArrayUtils.nullToEmpty(parameterTypes); final 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>Invokes a named {@code 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} class * would match a {@code boolean} primitive.</p> * * <p>This is a convenient wrapper for * {@link #invokeStaticMethod(Class, String, Object[], Class[])}. * </p> * * @param cls invoke static method on this class * @param methodName get method with this name * @param args use these arguments - treat {@code 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(final Class<?> cls, final String methodName, Object... args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { args = ArrayUtils.nullToEmpty(args); final Class<?>[] parameterTypes = ClassUtils.toClass(args); return invokeStaticMethod(cls, methodName, args, parameterTypes); } /** * <p>Invokes a named {@code 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} class * would match a {@code boolean} primitive.</p> * * * @param cls invoke static method on this class * @param methodName get method with this name * @param args use these arguments - treat {@code null} as empty array * @param parameterTypes match these parameters - treat {@code 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(final Class<?> cls, final String methodName, Object[] args, Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { args = ArrayUtils.nullToEmpty(args); parameterTypes = ArrayUtils.nullToEmpty(parameterTypes); final 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>Invokes a {@code 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 {@code 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(final Class<?> cls, final String methodName, Object... args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { args = ArrayUtils.nullToEmpty(args); final Class<?>[] parameterTypes = ClassUtils.toClass(args); return invokeExactStaticMethod(cls, methodName, args, parameterTypes); } /** * <p>Returns 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}. * This is just a convenience wrapper for * {@link #getAccessibleMethod(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(final Class<?> cls, final String methodName, final Class<?>... parameterTypes) { try { return getAccessibleMethod(cls.getMethod(methodName, parameterTypes)); } catch (final NoSuchMethodException e) { return null; } } /** * <p>Returns 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}.</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 final Class<?> cls = method.getDeclaringClass(); if (Modifier.isPublic(cls.getModifiers())) { return method; } final String methodName = method.getName(); final 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>Returns 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}.</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} if not found */ private static Method getAccessibleMethodFromSuperclass(final Class<?> cls, final String methodName, final Class<?>... parameterTypes) { Class<?> parentClass = cls.getSuperclass(); while (parentClass != null) { if (Modifier.isPublic(parentClass.getModifiers())) { try { return parentClass.getMethod(methodName, parameterTypes); } catch (final NoSuchMethodException e) { return null; } } parentClass = parentClass.getSuperclass(); } return null; } /** * <p>Returns 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}.</p> * * <p>There isn't any good reason why this method must be {@code 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} if not found */ private static Method getAccessibleMethodFromInterfaceNest(Class<?> cls, final String methodName, final Class<?>... parameterTypes) { // Search up the superclass chain for (; cls != null; cls = cls.getSuperclass()) { // Check the implemented interfaces of the parent class final 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 { return interfaces[i].getDeclaredMethod(methodName, parameterTypes); } catch (final NoSuchMethodException e) { // NOPMD /* * Swallow, if no method is found after the loop then this * method returns null. */ } // Recursively check our parent interfaces final Method method = getAccessibleMethodFromInterfaceNest(interfaces[i], methodName, parameterTypes); if (method != null) { return method; } } } return null; } /** * <p>Finds 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> * * <p>This method can match primitive parameter by passing in wrapper classes. * For example, a {@code Boolean} will match a primitive {@code boolean} * parameter. * </p> * * @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(final Class<?> cls, final String methodName, final Class<?>... parameterTypes) { try { final Method method = cls.getMethod(methodName, parameterTypes); MemberUtils.setAccessibleWorkaround(method); return method; } catch (final NoSuchMethodException e) { // NOPMD - Swallow the exception } // search through all methods Method bestMatch = null; final Method[] methods = cls.getMethods(); for (final Method method : methods) { // compare name and parameters if (method.getName().equals(methodName) && ClassUtils.isAssignable(parameterTypes, method.getParameterTypes(), true)) { // get accessible version of method final Method accessibleMethod = getAccessibleMethod(method); if (accessibleMethod != null && (bestMatch == null || MemberUtils.compareParameterTypes(accessibleMethod.getParameterTypes(), bestMatch.getParameterTypes(), parameterTypes) < 0)) { bestMatch = accessibleMethod; } } } if (bestMatch != null) { MemberUtils.setAccessibleWorkaround(bestMatch); } return bestMatch; } /** * Get the hierarchy of overridden methods down to {@code result} respecting generics. * @param method lowest to consider * @param interfacesBehavior whether to search interfaces, {@code null} {@code implies} false * @return Set<Method> in ascending order from sub- to superclass * @throws NullPointerException if the specified method is {@code null} * @since 3.2 */ public static Set<Method> getOverrideHierarchy(final Method method, final Interfaces interfacesBehavior) { Validate.notNull(method); final Set<Method> result = new LinkedHashSet<Method>(); result.add(method); final Class<?>[] parameterTypes = method.getParameterTypes(); final Class<?> declaringClass = method.getDeclaringClass(); final Iterator<Class<?>> hierarchy = ClassUtils.hierarchy(declaringClass, interfacesBehavior).iterator(); //skip the declaring class :P hierarchy.next(); hierarchyTraversal: while (hierarchy.hasNext()) { final Class<?> c = hierarchy.next(); final Method m = getMatchingAccessibleMethod(c, method.getName(), parameterTypes); if (m == null) { continue; } if (Arrays.equals(m.getParameterTypes(), parameterTypes)) { // matches without generics result.add(m); continue; } // necessary to get arguments every time in the case that we are including interfaces final Map<TypeVariable<?>, Type> typeArguments = TypeUtils.getTypeArguments(declaringClass, m.getDeclaringClass()); for (int i = 0; i < parameterTypes.length; i++) { final Type childType = TypeUtils.unrollVariables(typeArguments, method.getGenericParameterTypes()[i]); final Type parentType = TypeUtils.unrollVariables(typeArguments, m.getGenericParameterTypes()[i]); if (!TypeUtils.equals(childType, parentType)) { continue hierarchyTraversal; } } result.add(m); } return result; } /** * Gets all methods of the given class that are annotated with the given annotation. * @param cls * the {@link Class} to query * @param annotationCls * the {@link java.lang.annotation.Annotation} that must be present on a method to be matched * @return an array of Methods (possibly empty). * @throws IllegalArgumentException * if the class or annotation are {@code null} * @since 3.4 */ public static Method[] getMethodsWithAnnotation(final Class<?> cls, final Class<? extends Annotation> annotationCls) { final List<Method> annotatedMethodsList = getMethodsListWithAnnotation(cls, annotationCls); return annotatedMethodsList.toArray(new Method[annotatedMethodsList.size()]); } /** * Gets all methods of the given class that are annotated with the given annotation. * @param cls * the {@link Class} to query * @param annotationCls * the {@link Annotation} that must be present on a method to be matched * @return a list of Methods (possibly empty). * @throws IllegalArgumentException * if the class or annotation are {@code null} * @since 3.4 */ public static List<Method> getMethodsListWithAnnotation(final Class<?> cls, final Class<? extends Annotation> annotationCls) { Validate.isTrue(cls != null, "The class must not be null"); Validate.isTrue(annotationCls != null, "The annotation class must not be null"); final Method[] allMethods = cls.getMethods(); final List<Method> annotatedMethods = new ArrayList<Method>(); for (final Method method : allMethods) { if (method.getAnnotation(annotationCls) != null) { annotatedMethods.add(method); } } return annotatedMethods; } }