URLCLExternalClassRepository.java

/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.mappingsmodel.spi.meta.classloader;

import java.io.File;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.eclipse.persistence.tools.workbench.mappingsmodel.spi.meta.ExternalClassDescription;
import org.eclipse.persistence.tools.workbench.utility.Classpath;
import org.eclipse.persistence.tools.workbench.utility.CollectionTools;


/**
 * This external class repository uses a URLClassLoader to load classes
 * on the "project" classpath.
 */
final class URLCLExternalClassRepository
    extends AbstractCLExternalClassRepository
{

    /**
     * Cache the "project" classpath with all its entries
     * fully qualified and duplicates stripped out, including
     * any duplicates of entries on the "system" classpath.
     */
    private final Classpath canonicalProjectClasspath;


    // ********** constructors **********

    /**
     * Construct a class repository for the specified "project" classpath.
     * The "system" classpath has already been determined and cannot be changed.
     * Convert the classpath: fully-qualify the entries and eliminate any duplicates.
     */
    URLCLExternalClassRepository(File[] classpath) {
        super();
        Classpath tempClasspath = new Classpath(this.fileNames(classpath)).compressed();
        Classpath completeClasspath = Classpath.completeClasspath();
        this.canonicalProjectClasspath = this.removeDuplicates(completeClasspath, tempClasspath);
    }

    /**
     * Return an array of the names of the specified files.
     */
    private String[] fileNames(File[] files) {
        int len = files.length;
        String[] fileNames = new String[len];
        for (int i = 0; i < len; i++) {
            fileNames[i] = files[i].getAbsolutePath();
        }
        return fileNames;
    }

    /**
     * Remove the entries in classpath2 that are already in classpath1
     * and return the resulting classpath.
     */
    private Classpath removeDuplicates(Classpath classpath1, Classpath classpath2) {
        Set classpathEntries1 = CollectionTools.set(classpath1.getEntries());
        List fileNames = new ArrayList();
        Classpath.Entry[] entries2 = classpath2.getEntries();
        int len = entries2.length;
        for (int i = 0; i < len; i++) {
            Classpath.Entry entry2 = entries2[i];
            if ( ! classpathEntries1.contains(entry2)) {
                fileNames.add(entry2.fileName());
            }
        }
        return new Classpath(fileNames);
    }


    // ********** AbstractCLExternalClassRepository implementation **********

    /**
     * @see org.eclipse.persistence.tools.workbench.mappingsmodel.spi.meta.ExternalClassRepository#getExternalClassDescription(String)
     */
    public ExternalClassDescription getClassDescription(String className) {
        // postponing suffering even more; some queries only need classes that are on the system classpath;
        // if the project classpath is large, buildClassDescriptions() in the superclass can hang...
        ExternalClassDescription ecd = SystemCLExternalClassRepository.instance().getClassDescription(className);
        if (ecd != null)
            return ecd;

        return super.getClassDescription(className);
    }

    /**
     * @see AbstractCLExternalClassRepository#buildClassDescriptions()
     */
    Map buildClassDescriptions() {
        Map classDescriptions = new HashMap(20000);    // let's start large
        // first add the "system" classes
        SystemCLExternalClassRepository.instance().addClassDescriptionsTo(classDescriptions);
        // then add the "project" classes
        this.addClassDescriptionsFromClasspathTo(this.canonicalProjectClasspath, classDescriptions);
        return classDescriptions;
    }

    /**
     * @see AbstractCLExternalClassRepository#buildClassLoader()
     */
    ClassLoader buildClassLoader() {
        return new URLClassLoader(this.canonicalProjectClasspath.urls());
    }

}