| 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 | import java.util.ArrayList; |
| 22 | import java.util.Arrays; |
| 23 | import java.util.List; |
| 24 | |
| 25 | import org.springframework.beans.factory.InitializingBean; |
| 26 | import org.springframework.util.Assert; |
| 27 | import org.springframework.util.MethodInvoker; |
| 28 | |
| 29 | /** |
| 30 | * Superclass for delegating classes which dynamically call a custom method of |
| 31 | * injected object. Provides convenient API for dynamic method invocation |
| 32 | * shielding subclasses from low-level details and exception handling. |
| 33 | * |
| 34 | * {@link Exception}s thrown by a successfully invoked delegate method are |
| 35 | * re-thrown without wrapping. In case the delegate method throws a |
| 36 | * {@link Throwable} that doesn't subclass {@link Exception} it will be wrapped |
| 37 | * by {@link InvocationTargetThrowableWrapper}. |
| 38 | * |
| 39 | * @author Robert Kasanicky |
| 40 | */ |
| 41 | public abstract class AbstractMethodInvokingDelegator<T> implements InitializingBean { |
| 42 | |
| 43 | private Object targetObject; |
| 44 | |
| 45 | private String targetMethod; |
| 46 | |
| 47 | private Object[] arguments; |
| 48 | |
| 49 | /** |
| 50 | * Invoker the target method with arguments set by |
| 51 | * {@link #setArguments(Object[])}. |
| 52 | * @return object returned by invoked method |
| 53 | * @throws DynamicMethodInvocationException if the {@link MethodInvoker} |
| 54 | * used throws exception |
| 55 | */ |
| 56 | protected T invokeDelegateMethod() throws Exception { |
| 57 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 58 | invoker.setArguments(arguments); |
| 59 | return doInvoke(invoker); |
| 60 | } |
| 61 | |
| 62 | /** |
| 63 | * Invokes the target method with given argument. |
| 64 | * @param object argument for the target method |
| 65 | * @return object returned by target method |
| 66 | * @throws DynamicMethodInvocationException if the {@link MethodInvoker} |
| 67 | * used throws exception |
| 68 | */ |
| 69 | protected T invokeDelegateMethodWithArgument(Object object) throws Exception { |
| 70 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 71 | invoker.setArguments(new Object[] { object }); |
| 72 | return doInvoke(invoker); |
| 73 | } |
| 74 | |
| 75 | /** |
| 76 | * Invokes the target method with given arguments. |
| 77 | * @param args arguments for the invoked method |
| 78 | * @return object returned by invoked method |
| 79 | * @throws DynamicMethodInvocationException if the {@link MethodInvoker} |
| 80 | * used throws exception |
| 81 | */ |
| 82 | protected T invokeDelegateMethodWithArguments(Object[] args) throws Exception { |
| 83 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 84 | invoker.setArguments(args); |
| 85 | return doInvoke(invoker); |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Create a new configured instance of {@link MethodInvoker}. |
| 90 | */ |
| 91 | private MethodInvoker createMethodInvoker(Object targetObject, String targetMethod) { |
| 92 | HippyMethodInvoker invoker = new HippyMethodInvoker(); |
| 93 | invoker.setTargetObject(targetObject); |
| 94 | invoker.setTargetMethod(targetMethod); |
| 95 | invoker.setArguments(arguments); |
| 96 | return invoker; |
| 97 | } |
| 98 | |
| 99 | /** |
| 100 | * Prepare and invoke the invoker, rethrow checked exceptions as unchecked. |
| 101 | * @param invoker configured invoker |
| 102 | * @return return value of the invoked method |
| 103 | */ |
| 104 | @SuppressWarnings("unchecked") |
| 105 | private T doInvoke(MethodInvoker invoker) throws Exception { |
| 106 | try { |
| 107 | invoker.prepare(); |
| 108 | } |
| 109 | catch (ClassNotFoundException e) { |
| 110 | throw new DynamicMethodInvocationException(e); |
| 111 | } |
| 112 | catch (NoSuchMethodException e) { |
| 113 | throw new DynamicMethodInvocationException(e); |
| 114 | } |
| 115 | |
| 116 | try { |
| 117 | return (T) invoker.invoke(); |
| 118 | } |
| 119 | catch (InvocationTargetException e) { |
| 120 | if (e.getCause() instanceof Exception) { |
| 121 | throw (Exception) e.getCause(); |
| 122 | } |
| 123 | else { |
| 124 | throw new InvocationTargetThrowableWrapper(e.getCause()); |
| 125 | } |
| 126 | } |
| 127 | catch (IllegalAccessException e) { |
| 128 | throw new DynamicMethodInvocationException(e); |
| 129 | } |
| 130 | } |
| 131 | |
| 132 | public void afterPropertiesSet() throws Exception { |
| 133 | Assert.notNull(targetObject); |
| 134 | Assert.hasLength(targetMethod); |
| 135 | Assert.state(targetClassDeclaresTargetMethod(), |
| 136 | "target class must declare a method with matching name and parameter types"); |
| 137 | } |
| 138 | |
| 139 | /** |
| 140 | * @return true if target class declares a method matching target method |
| 141 | * name with given number of arguments of appropriate type. |
| 142 | */ |
| 143 | private boolean targetClassDeclaresTargetMethod() { |
| 144 | MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod); |
| 145 | |
| 146 | Method[] memberMethods = invoker.getTargetClass().getMethods(); |
| 147 | Method[] declaredMethods = invoker.getTargetClass().getDeclaredMethods(); |
| 148 | |
| 149 | List<Method> allMethods = new ArrayList<Method>(); |
| 150 | allMethods.addAll(Arrays.asList(memberMethods)); |
| 151 | allMethods.addAll(Arrays.asList(declaredMethods)); |
| 152 | |
| 153 | String targetMethodName = invoker.getTargetMethod(); |
| 154 | |
| 155 | for (Method method : allMethods) { |
| 156 | if (method.getName().equals(targetMethodName)) { |
| 157 | Class<?>[] params = method.getParameterTypes(); |
| 158 | if (arguments == null) { |
| 159 | // don't check signature, assume arguments will be supplied |
| 160 | // correctly at runtime |
| 161 | return true; |
| 162 | } |
| 163 | if (arguments.length == params.length) { |
| 164 | boolean argumentsMatchParameters = true; |
| 165 | for (int j = 0; j < params.length; j++) { |
| 166 | if (arguments[j] == null) { |
| 167 | continue; |
| 168 | } |
| 169 | if (!(params[j].isAssignableFrom(arguments[j].getClass()))) { |
| 170 | argumentsMatchParameters = false; |
| 171 | } |
| 172 | } |
| 173 | if (argumentsMatchParameters) |
| 174 | return true; |
| 175 | } |
| 176 | } |
| 177 | } |
| 178 | |
| 179 | return false; |
| 180 | } |
| 181 | |
| 182 | /** |
| 183 | * @param targetObject the delegate - bean id can be used to set this value |
| 184 | * in Spring configuration |
| 185 | */ |
| 186 | public void setTargetObject(Object targetObject) { |
| 187 | this.targetObject = targetObject; |
| 188 | } |
| 189 | |
| 190 | /** |
| 191 | * @param targetMethod name of the method to be invoked on |
| 192 | * {@link #setTargetObject(Object)}. |
| 193 | */ |
| 194 | public void setTargetMethod(String targetMethod) { |
| 195 | this.targetMethod = targetMethod; |
| 196 | } |
| 197 | |
| 198 | /** |
| 199 | * @param arguments arguments values for the { |
| 200 | * {@link #setTargetMethod(String)}. These will be used only when the |
| 201 | * subclass tries to invoke the target method without providing explicit |
| 202 | * argument values. |
| 203 | * |
| 204 | * If arguments are set to not-null value {@link #afterPropertiesSet()} will |
| 205 | * check the values are compatible with target method's signature. In case |
| 206 | * arguments are null (not set) method signature will not be checked and it |
| 207 | * is assumed correct values will be supplied at runtime. |
| 208 | */ |
| 209 | public void setArguments(Object[] arguments) { |
| 210 | this.arguments = arguments == null ? null : Arrays.asList(arguments).toArray(); |
| 211 | } |
| 212 | |
| 213 | /** |
| 214 | * Used to wrap a {@link Throwable} (not an {@link Exception}) thrown by a |
| 215 | * reflectively-invoked delegate. |
| 216 | * |
| 217 | * @author Robert Kasanicky |
| 218 | */ |
| 219 | public static class InvocationTargetThrowableWrapper extends RuntimeException { |
| 220 | |
| 221 | public InvocationTargetThrowableWrapper(Throwable cause) { |
| 222 | super(cause); |
| 223 | } |
| 224 | |
| 225 | } |
| 226 | } |