/*
* Copyright 2001-2004 The Apache Software Foundation
*
* 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.apache.commons.collections.functors;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import org.apache.commons.collections.FunctorException;
import org.apache.commons.collections.Transformer;
/**
* Transformer implementation that creates a new object instance by reflection.
*
* @since Commons Collections 3.0
* @version $Revision: 348444 $ $Date: 2005-11-23 14:06:56 +0000 (Wed, 23 Nov 2005) $
*
* @author Stephen Colebourne
*/
public class InvokerTransformer implements Transformer, Serializable {
/** The serial version */
private static final long serialVersionUID = -8653385846894047688L;
/** The method name to call */
private final String iMethodName;
/** The array of reflection parameter types */
private final Class[] iParamTypes;
/** The array of reflection arguments */
private final Object[] iArgs;
/**
* Gets an instance of this transformer calling a specific method with no arguments.
*
* @param methodName the method name to call
* @return an invoker transformer
* @since Commons Collections 3.1
*/
public static Transformer getInstance(String methodName) {
if (methodName == null) {
throw new IllegalArgumentException("The method to invoke must not be null");
}
return new InvokerTransformer(methodName);
}
/**
* Gets an instance of this transformer calling a specific method with specific values.
*
* @param methodName the method name to call
* @param paramTypes the parameter types of the method
* @param args the arguments to pass to the method
* @return an invoker transformer
*/
public static Transformer getInstance(String methodName, Class[] paramTypes, Object[] args) {
if (methodName == null) {
throw new IllegalArgumentException("The method to invoke must not be null");
}
if (((paramTypes == null) && (args != null))
|| ((paramTypes != null) && (args == null))
|| ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) {
throw new IllegalArgumentException("The parameter types must match the arguments");
}
if (paramTypes == null || paramTypes.length == 0) {
return new InvokerTransformer(methodName);
} else {
paramTypes = (Class[]) paramTypes.clone();
args = (Object[]) args.clone();
return new InvokerTransformer(methodName, paramTypes, args);
}
}
/**
* Constructor for no arg instance.
*
* @param methodName the method to call
*/
private InvokerTransformer(String methodName) {
super();
iMethodName = methodName;
iParamTypes = null;
iArgs = null;
}
/**
* Constructor that performs no validation.
* Use <code>getInstance</code> if you want that.
*
* @param methodName the method to call
* @param paramTypes the constructor parameter types, not cloned
* @param args the constructor arguments, not cloned
*/
public InvokerTransformer(String methodName, Class[] paramTypes, Object[] args) {
super();
iMethodName = methodName;
iParamTypes = paramTypes;
iArgs = args;
}
/**
* Transforms the input to result by invoking a method on the input.
*
* @param input the input object to transform
* @return the transformed result, null if null input
*/
public Object transform(Object input) {
if (input == null) {
return null;
}
try {
Class cls = input.getClass();
Method method = cls.getMethod(iMethodName, iParamTypes);
return method.invoke(input, iArgs);
} catch (NoSuchMethodException ex) {
throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' does not exist");
} catch (IllegalAccessException ex) {
throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' cannot be accessed");
} catch (InvocationTargetException ex) {
throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' threw an exception", ex);
}
}
}