org.springframework.webflow.util.DispatchMethodInvoker Maven / Gradle / Ivy
/*
* Copyright 2002-2006 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 org.springframework.webflow.util;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;
import org.springframework.binding.method.ClassMethodKey;
import org.springframework.binding.method.InvalidMethodSignatureException;
import org.springframework.core.NestedRuntimeException;
import org.springframework.util.Assert;
import org.springframework.util.CachingMapDecorator;
import org.springframework.util.ClassUtils;
/**
* Invoker and cache for dispatch methods that all share the same target object.
* The dispatch methods typically share the same form, but multiple exist per
* target object, and they only differ in name.
*
* @author Keith Donald
* @author Ben Hale
*/
public class DispatchMethodInvoker {
/**
* The target object to dispatch to.
*/
private Object target;
/**
* The parameter types describing the dispatch method signature.
*/
private Class[] parameterTypes;
/**
* The resolved method cache.
*/
private Map methodCache = new CachingMapDecorator() {
public Object create(Object key) {
String methodName = (String)key;
try {
return new ClassMethodKey(target.getClass(), methodName, parameterTypes).getMethod();
}
catch (InvalidMethodSignatureException e) {
throw new MethodLookupException("Unable to resolve dispatch method with name '" + methodName
+ "' and signature '" + getSignatureString(methodName)
+ "'; make sure the method name is correct and such a method is defined on targetClass "
+ target.getClass().getName(), e);
}
}
};
/**
* Creates a dispatch method invoker.
* @param target the target to dispatch to
* @param parameterTypes the parameter types defining the argument signature
* of the dispatch methods
*/
public DispatchMethodInvoker(Object target, Class[] parameterTypes) {
Assert.notNull(target, "The target of a dispatch method invocation is required");
this.target = target;
this.parameterTypes = parameterTypes;
}
/**
* Returns the target object method calls are dispatched to.
*/
public Object getTarget() {
return target;
}
/**
* Returns the parameter types defining the argument signature of the
* dispatch methods.
*/
public Class[] getParameterTypes() {
return parameterTypes;
}
/**
* Dispatch a call with given arguments to named dispatcher method.
* @param methodName the name of the method to invoke
* @param arguments the arguments to pass to the method
* @return the result of the method invokation
* @throws MethodLookupException when the method cannot be resolved
* @throws Exception when the invoked method throws an exception
*/
public Object invoke(String methodName, Object[] arguments) throws MethodLookupException, Exception {
try {
Method dispatchMethod = getDispatchMethod(methodName);
return dispatchMethod.invoke(target, arguments);
}
catch (InvocationTargetException e) {
// the invoced method threw an exception; have it propagate to the caller
Throwable t = e.getTargetException();
if (t instanceof Exception) {
throw (Exception)e.getTargetException();
}
else {
throw (Error)e.getTargetException();
}
}
}
/**
* Get a handle to the method of the specified name, with the signature
* defined by the configured parameter types and return type.
* @param methodName the method name
* @return the method
* @throws MethodLookupException when the method cannot be resolved
*/
private Method getDispatchMethod(String methodName) throws MethodLookupException {
return (Method)methodCache.get(methodName);
}
/**
* Returns the signature of the dispatch methods invoked by this class.
* @param methodName name of the dispatch method
*/
private String getSignatureString(String methodName) {
return methodName + "(" + getParameterTypesString() + ");";
}
/**
* Convenience method that returns the parameter types describing the
* signature of the dispatch method as a string.
*/
private String getParameterTypesString() {
StringBuffer parameterTypesString = new StringBuffer();
for (int i = 0; i < parameterTypes.length; i++) {
parameterTypesString.append(ClassUtils.getShortName(parameterTypes[i]));
if (i < parameterTypes.length - 1) {
parameterTypesString.append(',');
}
}
return parameterTypesString.toString();
}
/**
* Thrown when a dispatch method could not be resolved.
*/
public static class MethodLookupException extends NestedRuntimeException {
/**
* Create a new method lookup exception.
* @param msg a descriptive message
* @param ex the underlying cause of this exception
*/
public MethodLookupException(String msg, Throwable ex) {
super(msg, ex);
}
}
}