extscript-root-1.0.4/extscript-core-root/extscript-core/src/main/java/org/apache/myfaces/extensions/scripting/core/engine/ThrowAwayClassloader.java

/*
 * 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.myfaces.extensions.scripting.core.engine;

import org.apache.myfaces.extensions.scripting.core.api.WeavingContext;
import org.apache.myfaces.extensions.scripting.core.common.util.ClassUtils;
import org.apache.myfaces.extensions.scripting.core.monitor.ClassResource;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.logging.Level;
import java.util.logging.Logger;

import static java.util.logging.Level.SEVERE;

/**
 * @author Werner Punz (latest modification by $Author$)
 * @version $Revision$ $Date$
 */

public class ThrowAwayClassloader extends ClassLoader
{

    static final Logger _logger = Logger.getLogger(ThrowAwayClassloader.class.getName());
    boolean _untaint = true;
    public ThrowAwayClassloader(ClassLoader classLoader, boolean untaint)
    {
        super(classLoader);
        _untaint = untaint;
    }
    
    public ThrowAwayClassloader(ClassLoader classLoader)
    {
        super(classLoader);
    }

    public ThrowAwayClassloader()
    {
    }

    @Override
    protected Class<?> findClass(String s) throws ClassNotFoundException
    {
        return super.findClass(s);
    }

    @Override
    protected synchronized Class<?> loadClass(String s, boolean b) throws ClassNotFoundException
    {
        return super.loadClass(s, b);
    }

    @Override
    /**
     * load called either if the class is not loaded at all
     * or if the class has been recompiled (check upfront)
     */
    public Class<?> loadClass(String className) throws ClassNotFoundException
    {
        ClassResource res = (ClassResource) WeavingContext.getInstance().getResource(className);
        if (res == null) return super.loadClass(className);
        if (!res.isTainted() && res.getAClass() != null) return res.getAClass();
        File target = resolveClassFile(className);
        //a load must happen anyway because the target was recompiled
        int fileLength;
        byte[] fileContent;
        FileInputStream iStream = null;
        //we cannot load while a compile is in progress
        //we have to wait until it is one
        try
        {
            fileLength = (int) target.length();
            fileContent = new byte[fileLength];
            iStream = new FileInputStream(target);
            int result = iStream.read(fileContent);
            _logger.log(Level.FINER, "read {0} bytes", String.valueOf(result));
        }
        catch (FileNotFoundException e)
        {
            throw new ClassNotFoundException(e.toString());
        }
        catch (IOException e)
        {
            throw new ClassNotFoundException(e.toString());
        }
        finally
        {
            if (iStream != null)
            {
                try
                {
                    iStream.close();
                }
                catch (Exception e)
                {
                    Logger log = Logger.getLogger(this.getClass().getName());
                    log.log(SEVERE, "", e);
                }
            }
        }
        //here we use trick17 we can store as many classes of the same name
        //as long as we store with a new classloader every time it needs refresh
        //we need to do it because the classloader can call itself recursively
        //TODO we might run into issues here with inner classes
        Class retVal;
        if (res != null) {
            retVal = (new ThrowAwayClassloader(getParent(),_untaint)).defineClass(className, fileContent, 0, fileLength);
            if(_untaint) {
                res.setAClass(retVal);
                res.setTainted(false);
            }
        } else {
            retVal = super.defineClass(className, fileContent, 0, fileLength);
        }
        return retVal;

    }

    @Override
    public InputStream getResourceAsStream(String name)
    {                   
        File resource = new File(WeavingContext.getInstance().getConfiguration().getCompileTarget().getAbsolutePath()+File
                .separator+name); //resolveClassFile(name);
        if (resource.exists())
        {
            try
            {
                return new FileInputStream(resource);
            }
            catch (FileNotFoundException e)
            {
                return super.getResourceAsStream(name);
            }
        }
        return super.getResourceAsStream(name);
    }

    private File resolveClassFile(String name)
    {
        return ClassUtils.classNameToFile(WeavingContext.getInstance().getConfiguration().getCompileTarget()
                .getAbsolutePath
                (), name);

    }

}