ClassResource.java

/*
 * Carrot2 project.
 *
 * Copyright (C) 2002-2016, Dawid Weiss, Stanisław Osiński.
 * All rights reserved.
 *
 * Refer to the full license file "carrot2.LICENSE"
 * in the root folder of the repository checkout or at:
 * http://www.carrot2.org/carrot2.LICENSE
 */

package org.carrot2.util.resource;

import java.io.IOException;
import java.io.InputStream;

import org.carrot2.util.StreamUtils;
import org.simpleframework.xml.Attribute;
import org.simpleframework.xml.Root;
import org.simpleframework.xml.core.Commit;

/**
 * A resource relative to a class. This resource provider caches the content of returned
 * resources and closes the stream handle in {@link #open()}.
 */
@Root(name = "class-resource")
public final class ClassResource implements IResource
{
    /**
     * Instantiated class.
     */
    private Class<?> clazz;

    @Attribute(name = "classname")
    private String classname;

    @Attribute(name = "resource")
    private String resource;

    /* deserialization only. */
    ClassResource()
    {
    }

    public ClassResource(Class<?> clazz, String resource)
    {
        this.classname = clazz.getName();
        this.clazz = clazz;
        this.resource = resource;
    }

    /**
     * Override the default open-from-URL method so that we don't lock the source JAR.
     */
    @Override
    public InputStream open() throws IOException
    {
        if (clazz == null) {
            throw new IOException("Could not reinstantiate class: " + classname 
                + " from context class loader to "
                + " load resource: " + resource);
        }
        return StreamUtils.prefetch(clazz.getResourceAsStream(resource));
    }

    @Commit
    void afterDeserialization() throws ClassNotFoundException
    {
        // We have to try to reinstantiate the origin class now.
        ClassLoader cl = null;
        try {
          cl = Thread.currentThread().getContextClassLoader();
        } catch (SecurityException e) {
          // CCL not available.
        }

        if (cl == null)
        {
          cl = this.getClass().getClassLoader();
        }

        try
        {
            clazz = Class.forName(classname, false, cl);
        }
        catch (ClassNotFoundException e)
        {
            // Leave clazz empty, throw IOException later.
        }
    }
}