Source Code Cross Referenced for MethodInvoker.java in  » J2EE » spring-framework-2.5 » org » springframework » util » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » J2EE » spring framework 2.5 » org.springframework.util 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright 2002-2007 the original author or authors.
003:         *
004:         * Licensed under the Apache License, Version 2.0 (the "License");
005:         * you may not use this file except in compliance with the License.
006:         * You may obtain a copy of the License at
007:         *
008:         *      http://www.apache.org/licenses/LICENSE-2.0
009:         *
010:         * Unless required by applicable law or agreed to in writing, software
011:         * distributed under the License is distributed on an "AS IS" BASIS,
012:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013:         * See the License for the specific language governing permissions and
014:         * limitations under the License.
015:         */
016:
017:        package org.springframework.util;
018:
019:        import java.lang.reflect.InvocationTargetException;
020:        import java.lang.reflect.Method;
021:        import java.lang.reflect.Modifier;
022:
023:        /**
024:         * Helper class that allows for specifying a method to invoke in a declarative
025:         * fashion, be it static or non-static.
026:         *
027:         * <p>Usage: Specify "targetClass"/"targetMethod" or "targetObject"/"targetMethod",
028:         * optionally specify arguments, prepare the invoker. Afterwards, you may
029:         * invoke the method any number of times, obtaining the invocation result.
030:         *
031:         * <p>Typically not used directly but via its subclasses
032:         * {@link org.springframework.beans.factory.config.MethodInvokingFactoryBean} and
033:         * {@link org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean}.
034:         *
035:         * @author Colin Sampaleanu
036:         * @author Juergen Hoeller
037:         * @since 19.02.2004
038:         * @see #prepare
039:         * @see #invoke
040:         * @see org.springframework.beans.factory.config.MethodInvokingFactoryBean
041:         * @see org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean
042:         */
043:        public class MethodInvoker {
044:
045:            private Class targetClass;
046:
047:            private Object targetObject;
048:
049:            private String targetMethod;
050:
051:            private String staticMethod;
052:
053:            private Object[] arguments = new Object[0];
054:
055:            /** The method we will call */
056:            private Method methodObject;
057:
058:            /**
059:             * Set the target class on which to call the target method.
060:             * Only necessary when the target method is static; else,
061:             * a target object needs to be specified anyway.
062:             * @see #setTargetObject
063:             * @see #setTargetMethod
064:             */
065:            public void setTargetClass(Class targetClass) {
066:                this .targetClass = targetClass;
067:            }
068:
069:            /**
070:             * Return the target class on which to call the target method.
071:             */
072:            public Class getTargetClass() {
073:                return this .targetClass;
074:            }
075:
076:            /**
077:             * Set the target object on which to call the target method.
078:             * Only necessary when the target method is not static;
079:             * else, a target class is sufficient.
080:             * @see #setTargetClass
081:             * @see #setTargetMethod
082:             */
083:            public void setTargetObject(Object targetObject) {
084:                this .targetObject = targetObject;
085:                if (targetObject != null) {
086:                    this .targetClass = targetObject.getClass();
087:                }
088:            }
089:
090:            /**
091:             * Return the target object on which to call the target method.
092:             */
093:            public Object getTargetObject() {
094:                return this .targetObject;
095:            }
096:
097:            /**
098:             * Set the name of the method to be invoked.
099:             * Refers to either a static method or a non-static method,
100:             * depending on a target object being set.
101:             * @see #setTargetClass
102:             * @see #setTargetObject
103:             */
104:            public void setTargetMethod(String targetMethod) {
105:                this .targetMethod = targetMethod;
106:            }
107:
108:            /**
109:             * Return the name of the method to be invoked.
110:             */
111:            public String getTargetMethod() {
112:                return this .targetMethod;
113:            }
114:
115:            /**
116:             * Set a fully qualified static method name to invoke,
117:             * e.g. "example.MyExampleClass.myExampleMethod".
118:             * Convenient alternative to specifying targetClass and targetMethod.
119:             * @see #setTargetClass
120:             * @see #setTargetMethod
121:             */
122:            public void setStaticMethod(String staticMethod) {
123:                this .staticMethod = staticMethod;
124:            }
125:
126:            /**
127:             * Set arguments for the method invocation. If this property is not set,
128:             * or the Object array is of length 0, a method with no arguments is assumed.
129:             */
130:            public void setArguments(Object[] arguments) {
131:                this .arguments = (arguments != null ? arguments : new Object[0]);
132:            }
133:
134:            /**
135:             * Retrun the arguments for the method invocation.
136:             */
137:            public Object[] getArguments() {
138:                return this .arguments;
139:            }
140:
141:            /**
142:             * Prepare the specified method.
143:             * The method can be invoked any number of times afterwards.
144:             * @see #getPreparedMethod
145:             * @see #invoke
146:             */
147:            public void prepare() throws ClassNotFoundException,
148:                    NoSuchMethodException {
149:                if (this .staticMethod != null) {
150:                    int lastDotIndex = this .staticMethod.lastIndexOf('.');
151:                    if (lastDotIndex == -1
152:                            || lastDotIndex == this .staticMethod.length()) {
153:                        throw new IllegalArgumentException(
154:                                "staticMethod must be a fully qualified class plus method name: "
155:                                        + "e.g. 'example.MyExampleClass.myExampleMethod'");
156:                    }
157:                    String className = this .staticMethod.substring(0,
158:                            lastDotIndex);
159:                    String methodName = this .staticMethod
160:                            .substring(lastDotIndex + 1);
161:                    this .targetClass = resolveClassName(className);
162:                    this .targetMethod = methodName;
163:                }
164:
165:                Class targetClass = getTargetClass();
166:                String targetMethod = getTargetMethod();
167:                if (targetClass == null) {
168:                    throw new IllegalArgumentException(
169:                            "Either 'targetClass' or 'targetObject' is required");
170:                }
171:                if (targetMethod == null) {
172:                    throw new IllegalArgumentException(
173:                            "Property 'targetMethod' is required");
174:                }
175:
176:                Object[] arguments = getArguments();
177:                Class[] argTypes = new Class[arguments.length];
178:                for (int i = 0; i < arguments.length; ++i) {
179:                    argTypes[i] = (arguments[i] != null ? arguments[i]
180:                            .getClass() : Object.class);
181:                }
182:
183:                // Try to get the exact method first.
184:                try {
185:                    this .methodObject = targetClass.getMethod(targetMethod,
186:                            argTypes);
187:                } catch (NoSuchMethodException ex) {
188:                    // Just rethrow exception if we can't get any match.
189:                    this .methodObject = findMatchingMethod();
190:                    if (this .methodObject == null) {
191:                        throw ex;
192:                    }
193:                }
194:            }
195:
196:            /**
197:             * Resolve the given class name into a Class.
198:             * <p>The default implementations uses <code>ClassUtils.forName</code>,
199:             * using the thread context class loader.
200:             * @param className the class name to resolve
201:             * @return the resolved Class
202:             * @throws ClassNotFoundException if the class name was invalid
203:             */
204:            protected Class resolveClassName(String className)
205:                    throws ClassNotFoundException {
206:                return ClassUtils.forName(className);
207:            }
208:
209:            /**
210:             * Find a matching method with the specified name for the specified arguments.
211:             * @return a matching method, or <code>null</code> if none
212:             * @see #getTargetClass()
213:             * @see #getTargetMethod()
214:             * @see #getArguments()
215:             */
216:            protected Method findMatchingMethod() {
217:                String targetMethod = getTargetMethod();
218:                Object[] arguments = getArguments();
219:                int argCount = arguments.length;
220:
221:                Method[] candidates = getTargetClass().getMethods();
222:                Method matchingMethod = null;
223:                int numberOfMatchingMethods = 0;
224:
225:                for (int i = 0; i < candidates.length; i++) {
226:                    Method candidate = candidates[i];
227:                    Class[] paramTypes = candidate.getParameterTypes();
228:                    int paramCount = paramTypes.length;
229:                    if (candidate.getName().equals(targetMethod)
230:                            && paramCount == argCount) {
231:                        boolean match = true;
232:                        for (int j = 0; j < paramCount && match; j++) {
233:                            match = match
234:                                    && ClassUtils.isAssignableValue(
235:                                            paramTypes[j], arguments[j]);
236:                        }
237:                        if (match) {
238:                            matchingMethod = candidate;
239:                            numberOfMatchingMethods++;
240:                        }
241:                    }
242:                }
243:
244:                // Only return matching method if exactly one found.
245:                if (numberOfMatchingMethods == 1) {
246:                    return matchingMethod;
247:                } else {
248:                    return null;
249:                }
250:            }
251:
252:            /**
253:             * Return the prepared Method object that will be invoked.
254:             * <p>Can for example be used to determine the return type.
255:             * @return the prepared Method object (never <code>null</code>)
256:             * @throws IllegalStateException if the invoker hasn't been prepared yet
257:             * @see #prepare
258:             * @see #invoke
259:             */
260:            public Method getPreparedMethod() throws IllegalStateException {
261:                if (this .methodObject == null) {
262:                    throw new IllegalStateException(
263:                            "prepare() must be called prior to invoke() on MethodInvoker");
264:                }
265:                return this .methodObject;
266:            }
267:
268:            /**
269:             * Return whether this invoker has been prepared already,
270:             * i.e. whether it allows access to {@link #getPreparedMethod()} already.
271:             */
272:            public boolean isPrepared() {
273:                return (this .methodObject != null);
274:            }
275:
276:            /**
277:             * Invoke the specified method.
278:             * <p>The invoker needs to have been prepared before.
279:             * @return the object (possibly null) returned by the method invocation,
280:             * or <code>null</code> if the method has a void return type
281:             * @throws InvocationTargetException if the target method threw an exception
282:             * @throws IllegalAccessException if the target method couldn't be accessed
283:             * @see #prepare
284:             */
285:            public Object invoke() throws InvocationTargetException,
286:                    IllegalAccessException {
287:                // In the static case, target will simply be <code>null</code>.
288:                Object targetObject = getTargetObject();
289:                Method preparedMethod = getPreparedMethod();
290:                if (targetObject == null
291:                        && !Modifier.isStatic(preparedMethod.getModifiers())) {
292:                    throw new IllegalArgumentException(
293:                            "Target method must not be non-static without a target");
294:                }
295:                return preparedMethod.invoke(targetObject, getArguments());
296:            }
297:
298:        }
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