org.springframework.cloud.dataflow.app.utils.ClassloaderUtils.java Source code

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Here is the source code for org.springframework.cloud.dataflow.app.utils.ClassloaderUtils.java

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/*
 * Copyright 2015 the original author or authors.
 *
 * 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 org.springframework.cloud.dataflow.app.utils;

import java.net.URL;
import java.net.URLClassLoader;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.boot.loader.LaunchedURLClassLoader;
import org.springframework.util.StringUtils;

/**
 * @author Marius Bogoevici
 */
public class ClassloaderUtils {

    private static final Log log = LogFactory.getLog(ClassloaderUtils.class);

    /**
     * Creates a ClassLoader for the launched modules by merging the URLs supplied as argument with the URLs that
     * make up the additional classpath of the launched JVM (retrieved from the application classloader), and
     * setting the extension classloader of the JVM as parent, if accessible.
     *
     * @param urls a list of library URLs
     * @return the resulting classloader
     */
    public static ClassLoader createModuleClassloader(URL[] urls) {
        ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
        if (log.isDebugEnabled()) {
            log.debug("systemClassLoader is " + systemClassLoader);
        }
        if (systemClassLoader instanceof URLClassLoader) {
            // add the URLs of the application classloader to the created classloader
            // to compensate for LaunchedURLClassLoader not delegating to parent to retrieve resources
            @SuppressWarnings("resource")
            URLClassLoader systemUrlClassLoader = (URLClassLoader) systemClassLoader;
            URL[] mergedUrls = new URL[urls.length + systemUrlClassLoader.getURLs().length];
            if (log.isDebugEnabled()) {
                log.debug("Original URLs: " + StringUtils.arrayToCommaDelimitedString(urls));
                log.debug("Java Classpath URLs: "
                        + StringUtils.arrayToCommaDelimitedString(systemUrlClassLoader.getURLs()));
            }
            System.arraycopy(urls, 0, mergedUrls, 0, urls.length);
            System.arraycopy(systemUrlClassLoader.getURLs(), 0, mergedUrls, urls.length,
                    systemUrlClassLoader.getURLs().length);
            // add the extension classloader as parent to the created context, if accessible
            if (log.isDebugEnabled()) {
                log.debug("Classloader URLs: " + StringUtils.arrayToCommaDelimitedString(mergedUrls));
            }
            return new LaunchedURLClassLoader(mergedUrls, systemUrlClassLoader.getParent());
        }
        return new LaunchedURLClassLoader(urls, systemClassLoader);
    }
}