| 1 | /* |
| 2 | * Copyright 2006-2007 the original author or authors. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package org.springframework.batch.item.adapter; |
| 18 | |
| 19 | import java.lang.reflect.InvocationTargetException; |
| 20 | import java.lang.reflect.Method; |
| 21 | |
| 22 | import org.springframework.beans.factory.InitializingBean; |
| 23 | import org.springframework.util.Assert; |
| 24 | import org.springframework.util.MethodInvoker; |
| 25 | |
| 26 | /** |
| 27 | * Superclass for delegating classes which dynamically call a |
| 28 | * custom method of injected object. |
| 29 | * Provides convenient API for dynamic method invocation shielding |
| 30 | * subclasses from low-level details and exception handling. |
| 31 | * |
| 32 | * @author Robert Kasanicky |
| 33 | */ |
| 34 | public class AbstractMethodInvokingDelegator implements InitializingBean { |
| 35 | |
| 36 | private Object targetObject; |
| 37 | |
| 38 | private String targetMethod; |
| 39 | |
| 40 | private Object[] arguments; |
| 41 | |
| 42 | /** |
| 43 | * Invoker the target method with no arguments. |
| 44 | * @return object returned by invoked method |
| 45 | * @throws DynamicMethodInvocationException if the {@link MethodInvoker} used throws exception |
| 46 | */ |
| 47 | protected Object invokeDelegateMethod() { |
| 48 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 49 | invoker.setArguments(arguments); |
| 50 | return doInvoke(invoker); |
| 51 | } |
| 52 | |
| 53 | /** |
| 54 | * Invokes the target method with given argument. |
| 55 | * @param object argument for the target method |
| 56 | * @return object returned by target method |
| 57 | * @throws DynamicMethodInvocationException if the {@link MethodInvoker} used throws exception |
| 58 | */ |
| 59 | protected Object invokeDelegateMethodWithArgument(Object object) { |
| 60 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 61 | invoker.setArguments(new Object[]{object}); |
| 62 | return doInvoke(invoker); |
| 63 | } |
| 64 | |
| 65 | /** |
| 66 | * Invokes the target method with given arguments. |
| 67 | * @param args arguments for the invoked method |
| 68 | * @return object returned by invoked method |
| 69 | * @throws DynamicMethodInvocationException if the {@link MethodInvoker} used throws exception |
| 70 | */ |
| 71 | protected Object invokeDelegateMethodWithArguments(Object[] args) { |
| 72 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 73 | invoker.setArguments(args); |
| 74 | return doInvoke(invoker); |
| 75 | } |
| 76 | |
| 77 | /** |
| 78 | * Create a new configured instance of {@link MethodInvoker}. |
| 79 | */ |
| 80 | private MethodInvoker createMethodInvoker(Object targetObject, String targetMethod) { |
| 81 | MethodInvoker invoker = new MethodInvoker(); |
| 82 | invoker.setTargetObject(targetObject); |
| 83 | invoker.setTargetMethod(targetMethod); |
| 84 | invoker.setArguments(arguments); |
| 85 | return invoker; |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Prepare and invoke the invoker, rethrow checked exceptions as unchecked. |
| 90 | * @param invoker configured invoker |
| 91 | * @return return value of the invoked method |
| 92 | */ |
| 93 | private Object doInvoke(MethodInvoker invoker) { |
| 94 | try { |
| 95 | invoker.prepare(); |
| 96 | } |
| 97 | catch (ClassNotFoundException e) { |
| 98 | throw new DynamicMethodInvocationException(e); |
| 99 | } |
| 100 | catch (NoSuchMethodException e) { |
| 101 | throw new DynamicMethodInvocationException(e); |
| 102 | } |
| 103 | |
| 104 | try { |
| 105 | return invoker.invoke(); |
| 106 | } |
| 107 | catch (InvocationTargetException e) { |
| 108 | throw new DynamicMethodInvocationException(e); |
| 109 | } |
| 110 | catch (IllegalAccessException e) { |
| 111 | throw new DynamicMethodInvocationException(e); |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | public void afterPropertiesSet() throws Exception { |
| 116 | Assert.notNull(targetObject); |
| 117 | Assert.hasLength(targetMethod); |
| 118 | Assert.state(targetClassDeclaresTargetMethod(), |
| 119 | "target class must declare a method with name matching the target method"); |
| 120 | } |
| 121 | |
| 122 | /** |
| 123 | * @return true if target class declares a method matching target method name |
| 124 | * with given number of arguments of appropriate type. |
| 125 | */ |
| 126 | private boolean targetClassDeclaresTargetMethod() { |
| 127 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 128 | Method[] methods = invoker.getTargetClass().getDeclaredMethods(); |
| 129 | String targetMethodName = invoker.getTargetMethod(); |
| 130 | |
| 131 | for (int i=0; i < methods.length; i++) { |
| 132 | if (methods[i].getName().equals(targetMethodName)) { |
| 133 | Class[] params = methods[i].getParameterTypes(); |
| 134 | if (arguments == null) { |
| 135 | return true; |
| 136 | } else if (arguments.length == params.length) { |
| 137 | boolean argumentsMatchParameters = true; |
| 138 | for (int j = 0; j < params.length; j++) { |
| 139 | if (!(params[j].isAssignableFrom(arguments[j].getClass()))) { |
| 140 | argumentsMatchParameters = false; |
| 141 | } |
| 142 | } |
| 143 | if (argumentsMatchParameters) return true; |
| 144 | } |
| 145 | } |
| 146 | } |
| 147 | |
| 148 | return false; |
| 149 | } |
| 150 | |
| 151 | /** |
| 152 | * @param targetObject the delegate - bean id can be used to set this value in Spring configuration |
| 153 | */ |
| 154 | public void setTargetObject(Object targetObject) { |
| 155 | this.targetObject = targetObject; |
| 156 | } |
| 157 | |
| 158 | /** |
| 159 | * @param targetMethod name of the method to be invoked on {@link #setTargetObject(Object)}. |
| 160 | */ |
| 161 | public void setTargetMethod(String targetMethod) { |
| 162 | this.targetMethod = targetMethod; |
| 163 | } |
| 164 | |
| 165 | /** |
| 166 | * @param arguments arguments values for the {{@link #setTargetMethod(String)}. |
| 167 | * These are not expected to change during the lifetime of the delegator |
| 168 | * and will be used only when the subclass tries to invoke the target method |
| 169 | * without providing explicit argument values. |
| 170 | */ |
| 171 | public void setArguments(Object[] arguments) { |
| 172 | this.arguments = arguments; |
| 173 | } |
| 174 | } |