com.izforge.izpack.compiler.util.CompilerClassLoader Maven / Gradle / Ivy
/*
* IzPack - Copyright 2001-2012 Julien Ponge, All Rights Reserved.
*
* http://izpack.org/
* http://izpack.codehaus.org/
*
* Copyright 2012 Tim Anderson
*
* 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 com.izforge.izpack.compiler.util;
import java.net.URL;
import java.net.URLClassLoader;
import com.izforge.izpack.api.exception.IzPackClassNotFoundException;
/**
* Class loader for the compiler.
*
* This enables:
*
* - jars to be dynamically added
* - unqualified class names to be mapped to their fully qualified names
*
*
* @author Tim Anderson
*/
public class CompilerClassLoader extends URLClassLoader
{
/**
* The class name mapper.
*/
private final ClassNameMapper mapper;
/**
* Constructs a {@code CompilerClassLoader} using this class' class loader.
*
* @param mapper the class name mapper
*/
public CompilerClassLoader(ClassNameMapper mapper)
{
this(CompilerClassLoader.class.getClassLoader(), mapper);
}
/**
* Constructs a {@code CompilerClassLoader}.
*
* @param parent the parent class loader
* @param mapper the class name mapper
*/
public CompilerClassLoader(ClassLoader parent, ClassNameMapper mapper)
{
super(new URL[0], parent);
this.mapper = mapper;
}
/**
* Appends the specified URL to the list of URLs to search for classes and resources.
*
* @param url the URL to be added to the search path of URLs
*/
@Override
public void addURL(URL url)
{
super.addURL(url);
}
/**
* Loads the class with the specified name, ensuring it is of the specified type.
*
* This uses the {@link ClassNameMapper} to try and map it to a known class.
*
* @param name the class name
* @param type the expected type
* @return the corresponding class
* @throws ClassCastException if the class isn't of the specified type
* @throws IzPackClassNotFoundException if the class cannot be found
*/
@SuppressWarnings("unchecked")
public Class loadClass(String name, Class type)
{
Class result;
try
{
Class loaded = loadClass(name);
if (!type.isAssignableFrom(loaded))
{
throw new ClassCastException("Class " + loaded.getName() + " is not a " + type.getName());
}
else
{
result = (Class) loaded;
}
}
catch (ClassNotFoundException exception)
{
throw new IzPackClassNotFoundException(name, exception);
}
return result;
}
/**
* Finds the class with the specified name.
*
* This uses the {@link ClassNameMapper} to try and map it to a known class.
*
* @param name the name of the class
* @return the corresponding {@code Class} object
* @throws ClassNotFoundException if the class could not be found
*/
@Override
protected Class findClass(String name) throws ClassNotFoundException
{
Class result;
String mapping = mapper.map(name);
if (mapping != null)
{
result = loadClass(mapping);
}
else
{
result = super.findClass(name);
}
return result;
}
}