Java URL Connection closeURLClassLoader(URLClassLoader clazzLdr)

Description

This method is designed to clear out classloader file locks in windows.

License

Open Source License

Parameter

Parameter	Description
clazzLdr	class loader to clean up

Declaration

public static void closeURLClassLoader(URLClassLoader clazzLdr) 

Method Source Code

//package com.java2s;
/*/*from  w w w. j  av a 2 s  . co  m*/
 * This program is free software; you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
 * Foundation.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 * or from the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * Copyright (c) 2015 Pentaho Corporation. All rights reserved.
 */

import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Vector;
import java.util.jar.JarFile;

public class Main {
    /**
     * This method is designed to clear out classloader file locks in windows.
     *
     * @param clazzLdr class loader to clean up
     */
    public static void closeURLClassLoader(URLClassLoader clazzLdr) {
        HashSet<String> closedFiles = new HashSet<>();
        try {
            Object obj = getFieldObject(URLClassLoader.class, "ucp", clazzLdr);
            ArrayList loaders = (ArrayList) getFieldObject(obj.getClass(), "loaders", obj);
            for (Object ldr : loaders) {
                try {
                    JarFile file = (JarFile) getFieldObject(ldr.getClass(), "jar", ldr);
                    closedFiles.add(file.getName());
                    file.close();
                } catch (Exception e) {
                    // skip
                }
            }
        } catch (Exception e) {
            // skip
        }

        try {
            Vector nativeLibArr = (Vector) getFieldObject(ClassLoader.class, "nativeLibraries", clazzLdr);
            for (Object lib : nativeLibArr) {
                try {
                    Method fMethod = lib.getClass().getDeclaredMethod("finalize", new Class[0]);
                    fMethod.setAccessible(true);
                    fMethod.invoke(lib, new Object[0]);
                } catch (Exception e) {
                    // skip
                }
            }
        } catch (Exception e) {
            // skip
        }

        HashMap uCache = null;
        HashMap fCache = null;

        try {
            Class factory = getFieldObject(classForName("sun.net.www.protocol.jar.JarURLConnection"), "factory",
                    null).getClass();
            try {
                fCache = (HashMap) getFieldObject(factory, "fileCache", null);
            } catch (Exception e) {
                // skip
            }
            try {
                uCache = (HashMap) getFieldObject(factory, "urlCache", null);
            } catch (Exception e) {
                // skip
            }
            if (uCache != null) {
                for (Object file : ((HashMap) uCache.clone()).keySet()) {
                    if (file instanceof JarFile) {
                        JarFile jar = (JarFile) file;
                        if (!closedFiles.contains(jar.getName())) {
                            continue;
                        }
                        try {
                            jar.close();
                        } catch (IOException e) {
                            // skip
                        }
                        if (fCache != null) {
                            fCache.remove(uCache.get(jar));
                        }
                        uCache.remove(jar);
                    }
                }
            } else if (fCache != null) {
                for (Object key : ((HashMap) fCache.clone()).keySet()) {
                    Object file = fCache.get(key);
                    if (file instanceof JarFile) {
                        JarFile jar = (JarFile) file;
                        if (!closedFiles.contains(jar.getName())) {
                            continue;
                        }
                        try {
                            jar.close();
                        } catch (IOException e) {
                            // ignore
                        }
                        fCache.remove(key);
                    }
                }
            }
        } catch (Exception e) {
            // skip
        }
    }

    private static Object getFieldObject(Class clazz, String name, Object obj) throws Exception {
        Field field = clazz.getDeclaredField(name);
        field.setAccessible(true);
        return field.get(obj);
    }

    public static Class classForName(String name) throws ClassNotFoundException {
        try {
            ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
            if (contextClassLoader != null) {
                return contextClassLoader.loadClass(name);
            }
        } catch (Throwable ignore) {
        }
        return Class.forName(name);
    }
}

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2. addHeaders(URLConnection conn)
3. addProperty(URLConnection connection)
4. byteArrayToURL(final byte[] bytes)
5. createImgUrlConnection(String url)
6. createURLClassLoader(String dirPath)
7. createURLConnection(String url)
8. createWebStartDirectory(String name, String jarUrl)