Java tutorial
/* * Copyright 2002-2013 the original author or authors. * * Licensed 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 com.xiongyingqi.util; import java.lang.reflect.*; import java.sql.SQLException; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.regex.Pattern; /** * Simple utility class for working with the reflection API and handling * reflection exceptions. * <p/> * <p>Only intended for internal use. * * @author Juergen Hoeller * @author Rob Harrop * @author Rod Johnson * @author Costin Leau * @author Sam Brannen * @author Chris Beams * @since 1.2.2 */ public abstract class ReflectionUtils { private static final Pattern CGLIB_RENAMED_METHOD_PATTERN = Pattern.compile("CGLIB\\$(.+)\\$\\d+"); /** * Attempt to find a {@link java.lang.reflect.Field field} on the supplied {@link Class} with the * supplied {@code name}. Searches all superclasses up to {@link Object}. * * @param clazz the class to introspect * @param name the name of the field * @return the corresponding Field object, or {@code null} if not found */ public static Field findField(Class<?> clazz, String name) { return findField(clazz, name, null); } /** * Attempt to find a {@link java.lang.reflect.Field field} on the supplied {@link Class} with the * supplied {@code name} and/or {@link Class type}. Searches all superclasses * up to {@link Object}. * * @param clazz the class to introspect * @param name the name of the field (may be {@code null} if type is specified) * @param type the type of the field (may be {@code null} if name is specified) * @return the corresponding Field object, or {@code null} if not found */ public static Field findField(Class<?> clazz, String name, Class<?> type) { Assert.notNull(clazz, "Class must not be null"); Assert.isTrue(name != null || type != null, "Either name or type of the field must be specified"); Class<?> searchType = clazz; while (!Object.class.equals(searchType) && searchType != null) { Field[] fields = searchType.getDeclaredFields(); for (Field field : fields) { if ((name == null || name.equals(field.getName())) && (type == null || type.equals(field.getType()))) { return field; } } searchType = searchType.getSuperclass(); } return null; } /** * Set the field represented by the supplied {@link java.lang.reflect.Field field object} on the * specified {@link Object target object} to the specified {@code value}. * In accordance with {@link java.lang.reflect.Field#set(Object, Object)} semantics, the new value * is automatically unwrapped if the underlying field has a primitive type. * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException(Exception)}. * * @param field the field to set * @param target the target object on which to set the field * @param value the value to set; may be {@code null} */ public static void setField(Field field, Object target, Object value) { try { field.set(target, value); } catch (IllegalAccessException ex) { handleReflectionException(ex); throw new IllegalStateException( "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage()); } } /** * Get the field represented by the supplied {@link java.lang.reflect.Field field object} on the * specified {@link Object target object}. In accordance with {@link java.lang.reflect.Field#get(Object)} * semantics, the returned value is automatically wrapped if the underlying field * has a primitive type. * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException(Exception)}. * * @param field the field to get * @param target the target object from which to get the field * @return the field's current value */ public static Object getField(Field field, Object target) { try { return field.get(target); } catch (IllegalAccessException ex) { handleReflectionException(ex); throw new IllegalStateException( "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage()); } } /** * Attempt to find a {@link java.lang.reflect.Method} on the supplied class with the supplied name * and no parameters. Searches all superclasses up to {@code Object}. * <p>Returns {@code null} if no {@link java.lang.reflect.Method} can be found. * * @param clazz the class to introspect * @param name the name of the method * @return the Method object, or {@code null} if none found */ public static Method findMethod(Class<?> clazz, String name) { return findMethod(clazz, name, new Class<?>[0]); } /** * Attempt to find a {@link java.lang.reflect.Method} on the supplied class with the supplied name * and parameter types. Searches all superclasses up to {@code Object}. * <p>Returns {@code null} if no {@link java.lang.reflect.Method} can be found. * * @param clazz the class to introspect * @param name the name of the method * @param paramTypes the parameter types of the method * (may be {@code null} to indicate any signature) * @return the Method object, or {@code null} if none found */ public static Method findMethod(Class<?> clazz, String name, Class<?>... paramTypes) { Assert.notNull(clazz, "Class must not be null"); Assert.notNull(name, "Method name must not be null"); Class<?> searchType = clazz; while (searchType != null) { Method[] methods = (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods()); for (Method method : methods) { if (name.equals(method.getName()) && (paramTypes == null || Arrays.equals(paramTypes, method.getParameterTypes()))) { return method; } } searchType = searchType.getSuperclass(); } return null; } /** * Invoke the specified {@link java.lang.reflect.Method} against the supplied target object with no arguments. * The target object can be {@code null} when invoking a static {@link java.lang.reflect.Method}. * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}. * * @param method the method to invoke * @param target the target object to invoke the method on * @return the invocation result, if any * @see #invokeMethod(java.lang.reflect.Method, Object, Object[]) */ public static Object invokeMethod(Method method, Object target) { return invokeMethod(method, target, new Object[0]); } /** * Invoke the specified {@link java.lang.reflect.Method} against the supplied target object with the * supplied arguments. The target object can be {@code null} when invoking a * static {@link java.lang.reflect.Method}. * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}. * * @param method the method to invoke * @param target the target object to invoke the method on * @param args the invocation arguments (may be {@code null}) * @return the invocation result, if any */ public static Object invokeMethod(Method method, Object target, Object... args) { try { return method.invoke(target, args); } catch (Exception ex) { handleReflectionException(ex); } throw new IllegalStateException("Should never get here"); } /** * Invoke the specified JDBC API {@link java.lang.reflect.Method} against the supplied target * object with no arguments. * * @param method the method to invoke * @param target the target object to invoke the method on * @return the invocation result, if any * @throws java.sql.SQLException the JDBC API SQLException to rethrow (if any) * @see #invokeJdbcMethod(java.lang.reflect.Method, Object, Object[]) */ public static Object invokeJdbcMethod(Method method, Object target) throws SQLException { return invokeJdbcMethod(method, target, new Object[0]); } /** * Invoke the specified JDBC API {@link java.lang.reflect.Method} against the supplied target * object with the supplied arguments. * * @param method the method to invoke * @param target the target object to invoke the method on * @param args the invocation arguments (may be {@code null}) * @return the invocation result, if any * @throws java.sql.SQLException the JDBC API SQLException to rethrow (if any) * @see #invokeMethod(java.lang.reflect.Method, Object, Object[]) */ public static Object invokeJdbcMethod(Method method, Object target, Object... args) throws SQLException { try { return method.invoke(target, args); } catch (IllegalAccessException ex) { handleReflectionException(ex); } catch (InvocationTargetException ex) { if (ex.getTargetException() instanceof SQLException) { throw (SQLException) ex.getTargetException(); } handleInvocationTargetException(ex); } throw new IllegalStateException("Should never get here"); } /** * Handle the given reflection exception. Should only be called if no * checked exception is expected to be thrown by the target method. * <p>Throws the underlying RuntimeException or Error in case of an * InvocationTargetException with such a root cause. Throws an * IllegalStateException with an appropriate message else. * * @param ex the reflection exception to handle */ public static void handleReflectionException(Exception ex) { if (ex instanceof NoSuchMethodException) { throw new IllegalStateException("Method not found: " + ex.getMessage()); } if (ex instanceof IllegalAccessException) { throw new IllegalStateException("Could not access method: " + ex.getMessage()); } if (ex instanceof InvocationTargetException) { handleInvocationTargetException((InvocationTargetException) ex); } if (ex instanceof RuntimeException) { throw (RuntimeException) ex; } throw new UndeclaredThrowableException(ex); } /** * Handle the given invocation target exception. Should only be called if no * checked exception is expected to be thrown by the target method. * <p>Throws the underlying RuntimeException or Error in case of such a root * cause. Throws an IllegalStateException else. * * @param ex the invocation target exception to handle */ public static void handleInvocationTargetException(InvocationTargetException ex) { rethrowRuntimeException(ex.getTargetException()); } /** * Rethrow the given {@link Throwable exception}, which is presumably the * <em>target exception</em> of an {@link java.lang.reflect.InvocationTargetException}. Should * only be called if no checked exception is expected to be thrown by the * target method. * <p>Rethrows the underlying exception cast to an {@link RuntimeException} or * {@link Error} if appropriate; otherwise, throws an * {@link IllegalStateException}. * * @param ex the exception to rethrow * @throws RuntimeException the rethrown exception */ public static void rethrowRuntimeException(Throwable ex) { if (ex instanceof RuntimeException) { throw (RuntimeException) ex; } if (ex instanceof Error) { throw (Error) ex; } throw new UndeclaredThrowableException(ex); } /** * Rethrow the given {@link Throwable exception}, which is presumably the * <em>target exception</em> of an {@link java.lang.reflect.InvocationTargetException}. Should * only be called if no checked exception is expected to be thrown by the * target method. * <p>Rethrows the underlying exception cast to an {@link Exception} or * {@link Error} if appropriate; otherwise, throws an * {@link IllegalStateException}. * * @param ex the exception to rethrow * @throws Exception the rethrown exception (in case of a checked exception) */ public static void rethrowException(Throwable ex) throws Exception { if (ex instanceof Exception) { throw (Exception) ex; } if (ex instanceof Error) { throw (Error) ex; } throw new UndeclaredThrowableException(ex); } /** * Determine whether the given method explicitly declares the given * exception or one of its superclasses, which means that an exception of * that type can be propagated as-is within a reflective invocation. * * @param method the declaring method * @param exceptionType the exception to throw * @return {@code true} if the exception can be thrown as-is; * {@code false} if it needs to be wrapped */ public static boolean declaresException(Method method, Class<?> exceptionType) { Assert.notNull(method, "Method must not be null"); Class<?>[] declaredExceptions = method.getExceptionTypes(); for (Class<?> declaredException : declaredExceptions) { if (declaredException.isAssignableFrom(exceptionType)) { return true; } } return false; } /** * Determine whether the given field is a "public static final" constant. * * @param field the field to check */ public static boolean isPublicStaticFinal(Field field) { int modifiers = field.getModifiers(); return (Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers)); } /** * Determine whether the given method is an "equals" method. * * @see Object#equals(Object) */ public static boolean isEqualsMethod(Method method) { if (method == null || !method.getName().equals("equals")) { return false; } Class<?>[] paramTypes = method.getParameterTypes(); return (paramTypes.length == 1 && paramTypes[0] == Object.class); } /** * Determine whether the given method is a "hashCode" method. * * @see Object#hashCode() */ public static boolean isHashCodeMethod(Method method) { return (method != null && method.getName().equals("hashCode") && method.getParameterTypes().length == 0); } /** * Determine whether the given method is a "toString" method. * * @see Object#toString() */ public static boolean isToStringMethod(Method method) { return (method != null && method.getName().equals("toString") && method.getParameterTypes().length == 0); } /** * Determine whether the given method is originally declared by {@link Object}. */ public static boolean isObjectMethod(Method method) { try { Object.class.getDeclaredMethod(method.getName(), method.getParameterTypes()); return true; } catch (SecurityException ex) { return false; } catch (NoSuchMethodException ex) { return false; } } /** * Determine whether the given method is a CGLIB 'renamed' method, following * the pattern "CGLIB$methodName$0". * * @param renamedMethod the method to check * @see org.springframework.cglib.proxy.Enhancer#rename */ public static boolean isCglibRenamedMethod(Method renamedMethod) { return CGLIB_RENAMED_METHOD_PATTERN.matcher(renamedMethod.getName()).matches(); } /** * Make the given field accessible, explicitly setting it accessible if * necessary. The {@code setAccessible(true)} method is only called * when actually necessary, to avoid unnecessary conflicts with a JVM * SecurityManager (if active). * * @param field the field to make accessible * @see java.lang.reflect.Field#setAccessible */ public static void makeAccessible(Field field) { if ((!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers()) || Modifier.isFinal(field.getModifiers())) && !field.isAccessible()) { field.setAccessible(true); } } /** * Make the given method accessible, explicitly setting it accessible if * necessary. The {@code setAccessible(true)} method is only called * when actually necessary, to avoid unnecessary conflicts with a JVM * SecurityManager (if active). * * @param method the method to make accessible * @see java.lang.reflect.Method#setAccessible */ public static void makeAccessible(Method method) { if ((!Modifier.isPublic(method.getModifiers()) || !Modifier.isPublic(method.getDeclaringClass().getModifiers())) && !method.isAccessible()) { method.setAccessible(true); } } /** * Make the given constructor accessible, explicitly setting it accessible * if necessary. The {@code setAccessible(true)} method is only called * when actually necessary, to avoid unnecessary conflicts with a JVM * SecurityManager (if active). * * @param ctor the constructor to make accessible * @see java.lang.reflect.Constructor#setAccessible */ public static void makeAccessible(Constructor<?> ctor) { if ((!Modifier.isPublic(ctor.getModifiers()) || !Modifier.isPublic(ctor.getDeclaringClass().getModifiers())) && !ctor.isAccessible()) { ctor.setAccessible(true); } } /** * Perform the given callback operation on all matching methods of the given * class and superclasses. * <p>The same named method occurring on subclass and superclass will appear * twice, unless excluded by a {@link com.xiongyingqi.util.ReflectionUtils.MethodFilter}. * * @param clazz class to start looking at * @param mc the callback to invoke for each method * @see #doWithMethods(Class, com.xiongyingqi.util.ReflectionUtils.MethodCallback, com.xiongyingqi.util.ReflectionUtils.MethodFilter) */ public static void doWithMethods(Class<?> clazz, MethodCallback mc) throws IllegalArgumentException { doWithMethods(clazz, mc, null); } /** * Perform the given callback operation on all matching methods of the given * class and superclasses (or given interface and super-interfaces). * <p>The same named method occurring on subclass and superclass will appear * twice, unless excluded by the specified {@link com.xiongyingqi.util.ReflectionUtils.MethodFilter}. * * @param clazz class to start looking at * @param mc the callback to invoke for each method * @param mf the filter that determines the methods to apply the callback to */ public static void doWithMethods(Class<?> clazz, MethodCallback mc, MethodFilter mf) throws IllegalArgumentException { // Keep backing up the inheritance hierarchy. Method[] methods = clazz.getDeclaredMethods(); for (Method method : methods) { if (mf != null && !mf.matches(method)) { continue; } try { mc.doWith(method); } catch (IllegalAccessException ex) { throw new IllegalStateException( "Shouldn't be illegal to access method '" + method.getName() + "': " + ex); } } if (clazz.getSuperclass() != null) { doWithMethods(clazz.getSuperclass(), mc, mf); } else if (clazz.isInterface()) { for (Class<?> superIfc : clazz.getInterfaces()) { doWithMethods(superIfc, mc, mf); } } } /** * Get all declared methods on the leaf class and all superclasses. Leaf * class methods are included first. */ public static Method[] getAllDeclaredMethods(Class<?> leafClass) throws IllegalArgumentException { final List<Method> methods = new ArrayList<Method>(32); doWithMethods(leafClass, new MethodCallback() { @Override public void doWith(Method method) { methods.add(method); } }); return methods.toArray(new Method[methods.size()]); } /** * Get the unique set of declared methods on the leaf class and all superclasses. Leaf * class methods are included first and while traversing the superclass hierarchy any methods found * with signatures matching a method already included are filtered out. */ public static Method[] getUniqueDeclaredMethods(Class<?> leafClass) throws IllegalArgumentException { final List<Method> methods = new ArrayList<Method>(32); doWithMethods(leafClass, new MethodCallback() { @Override public void doWith(Method method) { boolean knownSignature = false; Method methodBeingOverriddenWithCovariantReturnType = null; for (Method existingMethod : methods) { if (method.getName().equals(existingMethod.getName()) && Arrays.equals(method.getParameterTypes(), existingMethod.getParameterTypes())) { // is this a covariant return type situation? if (existingMethod.getReturnType() != method.getReturnType() && existingMethod.getReturnType().isAssignableFrom(method.getReturnType())) { methodBeingOverriddenWithCovariantReturnType = existingMethod; } else { knownSignature = true; } break; } } if (methodBeingOverriddenWithCovariantReturnType != null) { methods.remove(methodBeingOverriddenWithCovariantReturnType); } if (!knownSignature && !isCglibRenamedMethod(method)) { methods.add(method); } } }); return methods.toArray(new Method[methods.size()]); } /** * Invoke the given callback on all fields in the target class, going up the * class hierarchy to get all declared fields. * * @param clazz the target class to analyze * @param fc the callback to invoke for each field */ public static void doWithFields(Class<?> clazz, FieldCallback fc) throws IllegalArgumentException { doWithFields(clazz, fc, null); } /** * Invoke the given callback on all fields in the target class, going up the * class hierarchy to get all declared fields. * * @param clazz the target class to analyze * @param fc the callback to invoke for each field * @param ff the filter that determines the fields to apply the callback to */ public static void doWithFields(Class<?> clazz, FieldCallback fc, FieldFilter ff) throws IllegalArgumentException { // Keep backing up the inheritance hierarchy. Class<?> targetClass = clazz; do { Field[] fields = targetClass.getDeclaredFields(); for (Field field : fields) { // Skip static and final fields. if (ff != null && !ff.matches(field)) { continue; } try { fc.doWith(field); } catch (IllegalAccessException ex) { throw new IllegalStateException( "Shouldn't be illegal to access field '" + field.getName() + "': " + ex); } } targetClass = targetClass.getSuperclass(); } while (targetClass != null && targetClass != Object.class); } /** * Given the source object and the destination, which must be the same class * or a subclass, copy all fields, including inherited fields. Designed to * work on objects with public no-arg constructors. * * @throws IllegalArgumentException if the arguments are incompatible */ public static void shallowCopyFieldState(final Object src, final Object dest) throws IllegalArgumentException { if (src == null) { throw new IllegalArgumentException("Source for field copy cannot be null"); } if (dest == null) { throw new IllegalArgumentException("Destination for field copy cannot be null"); } if (!src.getClass().isAssignableFrom(dest.getClass())) { throw new IllegalArgumentException("Destination class [" + dest.getClass().getName() + "] must be same or subclass as source class [" + src.getClass().getName() + "]"); } doWithFields(src.getClass(), new FieldCallback() { @Override public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException { makeAccessible(field); Object srcValue = field.get(src); field.set(dest, srcValue); } }, COPYABLE_FIELDS); } /** * Action to take on each method. */ public interface MethodCallback { /** * Perform an operation using the given method. * * @param method the method to operate on */ void doWith(Method method) throws IllegalArgumentException, IllegalAccessException; } /** * Callback optionally used to filter methods to be operated on by a method callback. */ public interface MethodFilter { /** * Determine whether the given method matches. * * @param method the method to check */ boolean matches(Method method); } /** * Callback interface invoked on each field in the hierarchy. */ public interface FieldCallback { /** * Perform an operation using the given field. * * @param field the field to operate on */ void doWith(Field field) throws IllegalArgumentException, IllegalAccessException; } /** * Callback optionally used to filter fields to be operated on by a field callback. */ public interface FieldFilter { /** * Determine whether the given field matches. * * @param field the field to check */ boolean matches(Field field); } /** * Pre-built FieldFilter that matches all non-static, non-final fields. */ public static FieldFilter COPYABLE_FIELDS = new FieldFilter() { @Override public boolean matches(Field field) { return !(Modifier.isStatic(field.getModifiers()) || Modifier.isFinal(field.getModifiers())); } }; /** * Pre-built MethodFilter that matches all non-bridge methods. */ public static MethodFilter NON_BRIDGED_METHODS = new MethodFilter() { @Override public boolean matches(Method method) { return !method.isBridge(); } }; /** * Pre-built MethodFilter that matches all non-bridge methods * which are not declared on {@code java.lang.Object}. */ public static MethodFilter USER_DECLARED_METHODS = new MethodFilter() { @Override public boolean matches(Method method) { return (!method.isBridge() && method.getDeclaringClass() != Object.class); } }; }