org.apache.commons.collections.functors.InstantiateFactory Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.Constructor;
import java.lang.reflect.InvocationTargetException;
import org.apache.commons.collections.Factory;
import org.apache.commons.collections.FunctorException;
/**
* Factory implementation that creates a new object instance by reflection.
*
* @since Commons Collections 3.0
* @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public class InstantiateFactory implements Factory, Serializable {
/** The serial version */
private static final long serialVersionUID = -7732226881069447957L;
/** The class to create */
private final Class iClassToInstantiate;
/** The constructor parameter types */
private final Class[] iParamTypes;
/** The constructor arguments */
private final Object[] iArgs;
/** The constructor */
private transient Constructor iConstructor = null;
/**
* Factory method that performs validation.
*
* @param classToInstantiate the class to instantiate, not null
* @param paramTypes the constructor parameter types
* @param args the constructor arguments
* @return a new instantiate factory
*/
public static Factory getInstance(Class classToInstantiate, Class[] paramTypes, Object[] args) {
if (classToInstantiate == null) {
throw new IllegalArgumentException("Class to instantiate must not be null");
}
if (((paramTypes == null) && (args != null))
|| ((paramTypes != null) && (args == null))
|| ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) {
throw new IllegalArgumentException("Parameter types must match the arguments");
}
if (paramTypes == null || paramTypes.length == 0) {
return new InstantiateFactory(classToInstantiate);
} else {
paramTypes = (Class[]) paramTypes.clone();
args = (Object[]) args.clone();
return new InstantiateFactory(classToInstantiate, paramTypes, args);
}
}
/**
* Constructor that performs no validation.
* Use getInstance if you want that.
*
* @param classToInstantiate the class to instantiate
*/
public InstantiateFactory(Class classToInstantiate) {
super();
iClassToInstantiate = classToInstantiate;
iParamTypes = null;
iArgs = null;
findConstructor();
}
/**
* Constructor that performs no validation.
* Use getInstance if you want that.
*
* @param classToInstantiate the class to instantiate
* @param paramTypes the constructor parameter types, not cloned
* @param args the constructor arguments, not cloned
*/
public InstantiateFactory(Class classToInstantiate, Class[] paramTypes, Object[] args) {
super();
iClassToInstantiate = classToInstantiate;
iParamTypes = paramTypes;
iArgs = args;
findConstructor();
}
/**
* Find the Constructor for the class specified.
*/
private void findConstructor() {
try {
iConstructor = iClassToInstantiate.getConstructor(iParamTypes);
} catch (NoSuchMethodException ex) {
throw new IllegalArgumentException("InstantiateFactory: The constructor must exist and be public ");
}
}
/**
* Creates an object using the stored constructor.
*
* @return the new object
*/
public Object create() {
// needed for post-serialization
if (iConstructor == null) {
findConstructor();
}
try {
return iConstructor.newInstance(iArgs);
} catch (InstantiationException ex) {
throw new FunctorException("InstantiateFactory: InstantiationException", ex);
} catch (IllegalAccessException ex) {
throw new FunctorException("InstantiateFactory: Constructor must be public", ex);
} catch (InvocationTargetException ex) {
throw new FunctorException("InstantiateFactory: Constructor threw an exception", ex);
}
}
}