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Java Tutorial » File » JarFile 
11.63.19.Search class in class path and Jar filesPrevious/Next
/*
 * $Id: ClassSearchUtils.java,v 1.1 2009/03/01 12:01:11 rah003 Exp $
 *
 * Copyright 2009 Sun Microsystems, Inc., 4150 Network Circle,
 * Santa Clara, California 95054, U.S.A. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 
 * This library 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.
 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

import java.awt.HeadlessException;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.StringTokenizer;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.logging.Logger;

public class ClassSearchUtils {

    private static final Logger log = Logger.getAnonymousLogger();

    /**
     * Classloader to be used to obtain resources from file system.
     */
    private ClassLoader classloader;

    /**
     * List of the resource found in the classpath.
     */
    private ArrayList list;

    /**
     * Extension of the resource to be found in the classpath.
     */
    private String extension;

    private String prefix;

    /**
     * Search for the resource with the extension in the classpath. Method
     * self-instantiate factory for every call to ensure thread safety.
     @param extension Mandatory extension of the resource. If all resources
     * are required extension should be empty string. Null extension is not
     * allowed and will cause method to fail.
     @return List of all resources with specified extension.
     */
    public static List<Class<?>> searchClassPath(String prefix) {
        return searchClassPath(prefix, ".class");
    }
    /**
     * Search for the resource with the extension in the classpath. Method
     * self-instantiate factory for every call to ensure thread safety.
     @param extension Mandatory extension of the resource. If all resources
     * are required extension should be empty string. Null extension is not
     * allowed and will cause method to fail.
     @return List of all resources with specified extension.
     */
    public static List searchClassPath(String prefix, String extension) {
        ClassSearchUtils factory = new ClassSearchUtils();
        factory.prefix = prefix;
        return factory.find(extension);
    }

    /**
     * Search for the resource with the extension in the classpath.
     @param extension Mandatory extension of the resource. If all resources
     * are required extension should be empty string. Null extension is not
     * allowed and will cause method to fail.
     @return List of all resources with specified extension.
     */
    private List<Class<?>> find(String extension) {
        this.extension = extension;
        this.list = new ArrayList();
        this.classloader = this.getClass().getClassLoader();
        String classpath = System.getProperty("java.class.path");

        try {
            Method method =
                this.classloader.getClass().getMethod("getClassPath"(Class<?>null);
            if (method != null) {
                classpath = (Stringmethod.invoke(this.classloader, (Objectnull);
            }
        catch (Exception e) {
            // ignore
        }
        if (classpath == null) {
            classpath = System.getProperty("java.class.path");
        }

        StringTokenizer tokenizer =
            new StringTokenizer(classpath, File.pathSeparator);
        String token;
        File dir;
        String name;
        while (tokenizer.hasMoreTokens()) {
            token = tokenizer.nextToken();
            dir = new File(token);
            if (dir.isDirectory()) {
                lookInDirectory("", dir);
            }
            if (dir.isFile()) {
                name = dir.getName().toLowerCase();
                if (name.endsWith(".zip"|| name.endsWith(".jar")) {
                    this.lookInArchive(dir);
                }
            }
        }
        return this.list;
    }

    /**
     @param name Name of to parent directories in java class notation (dot
     * separator)
     @param dir Directory to be searched for classes.
     */
    private void lookInDirectory(String name, File dir) {
        log.fine"Looking in directory [" + dir.getName() "].");
        File[] files = dir.listFiles();
        File file;
        String fileName;
        final int size = files.length;
        for (int i = 0; i < size; i++) {
            file = files[i];
            fileName = file.getName();
            if (file.isFile()
                && fileName.toLowerCase().endsWith(this.extension)) {
                try {
                    if (this.extension.equalsIgnoreCase(".class")) {
                        fileName = fileName.substring(0, fileName.length() 6);
                        // filter ignored resources
                        if (!(name + fileName).startsWith(this.prefix)) {
                            continue;
                        }

                        log.fine(
                            "Found class: [" + name + fileName + "].");
                        this.list.add(Class.forName(name + fileName));
                    else {
                        this.list.add(
                            this.classloader.getResource(
                                name.replace('.', File.separatorChar)
                                    + fileName));
                    }
                catch (ClassNotFoundException e) {
                    // ignore
                catch (NoClassDefFoundError e) {
                        //ignore too
                catch (ExceptionInInitializerError e) {
                    if (e.getCause() instanceof HeadlessException) {
                        // running in headless env ... ignore 
                    else {
                        throw e;
                    }
                }
            }
            // search recursively.
            // I don't like that but we will see how it will work.
            if (file.isDirectory()) {
                lookInDirectory(name + fileName + ".", file);
            }
        }

    }

    /**
     * Search archive files for required resource.
     @param archive Jar or zip to be searched for classes or other resources.
     */
    private void lookInArchive(File archive) {
        log.fine(
            "Looking in archive ["
                + archive.getName()
                "] for extension ["
                this.extension
                "].");
        JarFile jarFile = null;
        try {
            jarFile = new JarFile(archive);
        catch (IOException e) {
            log.warning(
                "Non fatal error. Unable to read jar item.");
            return;
        }
        Enumeration entries = jarFile.entries();
        JarEntry entry;
        String entryName;
        while (entries.hasMoreElements()) {
            entry = (JarEntryentries.nextElement();
            entryName = entry.getName();
            if (entryName.toLowerCase().endsWith(this.extension)) {
                try {
                    if (this.extension.equalsIgnoreCase(".class")) {
                        // convert name into java classloader notation
                        entryName =
                            entryName.substring(0, entryName.length() 6);
                        entryName = entryName.replace('/''.');

                        // filter ignored resources
                        if (!entryName.startsWith(this.prefix)) {
                            continue;
                        }

                        log.fine(
                            "Found class: [" + entryName + "]. ");
                        this.list.add(Class.forName(entryName));
                    else {
                        this.list.add(this.classloader.getResource(entryName));
                        log.fine(
                            "Found appropriate resource with name ["
                                + entryName
                                "]. Resource instance:"
                                this.classloader.getResource(entryName));
                    }
                catch (Throwable e) {
                    // ignore
                    log.warning(
                        "Unable to load resource ["
                            + entryName
                            "] form file ["
                            + archive.getAbsolutePath()
                            "].");
                }
            }
        }
    }
}
11.63.JarFile
11.63.1.Creating a JAR File
11.63.2.Create JarFile and use Pack200.Packer
11.63.3.List all file names in a jar file
11.63.4.Listing the Entries of a JAR File Manifest
11.63.5.Listing the Main Attributes in a JAR File Manifest
11.63.6.Retrieves the manifest from a JAR file and writes the manifest contents to a file.
11.63.7.Get uncompressed and compressed file size in a Jar file
11.63.8.Get zip method: ZipEntry.STORED, ZipEntry.DEFLATED
11.63.9.Get CRC code for each file in a Jar file
11.63.10.Get file comment
11.63.11.Get resource from Jar file
11.63.12.JAR Archives: Jar Lister
11.63.13.JAR Archives: Packer200
11.63.14.JAR Archives: Unpacker200
11.63.15.Jar Entry OutputStream
11.63.16.Get jar file Attribute
11.63.17.Get the jar entry
11.63.18.Get the jar file
11.63.19.Search class in class path and Jar files
11.63.20.Add jar contents to the deployment archive under the given prefix
11.63.21.Manifest Writer
11.63.22.Make Temp Jar
11.63.23.Load resource from Jar file
11.63.24.A class to find resources in the classpath by their mime-type specified in the MANIFEST.
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