https://openjdk.java.net/ 
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * particular file as subject to the "Classpath" exception as provided
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 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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package jdk.internal.util.jar;

import java.io.*;
import java.util.*;
import java.util.jar.*;
import java.util.zip.*;
import static sun.security.action.GetPropertyAction.privilegedGetProperty;


This class is used to maintain mappings from packages, classes
and resources to their enclosing JAR files. Mappings are kept
at the package level except for class or resource files that
are located at the root directory. URLClassLoader uses the mapping
information to determine where to fetch an extension class or
resource from.

Author: Zhenghua Li
Since:  1.3
/**
 * This class is used to maintain mappings from packages, classes
 * and resources to their enclosing JAR files. Mappings are kept
 * at the package level except for class or resource files that
 * are located at the root directory. URLClassLoader uses the mapping
 * information to determine where to fetch an extension class or
 * resource from.
 *
 * @author  Zhenghua Li
 * @since   1.3
 */

public class JarIndex {

    
The hash map that maintains mappings from
package/classe/resource to jar file list(s)

/**
     * The hash map that maintains mappings from
     * package/classe/resource to jar file list(s)
     */
    private HashMap<String,LinkedList<String>> indexMap;

    
The hash map that maintains mappings from
jar file to package/class/resource lists

/**
     * The hash map that maintains mappings from
     * jar file to package/class/resource lists
     */
    private HashMap<String,LinkedList<String>> jarMap;

    /*
     * An ordered list of jar file names.
     */
    private String[] jarFiles;

    
The index file name.

/**
     * The index file name.
     */
    public static final String INDEX_NAME = "META-INF/INDEX.LIST";

    
true if, and only if, sun.misc.JarIndex.metaInfFilenames is set to true.
If true, the names of the files in META-INF, and its subdirectories, will
be added to the index. Otherwise, just the directory names are added.

/**
     * true if, and only if, sun.misc.JarIndex.metaInfFilenames is set to true.
     * If true, the names of the files in META-INF, and its subdirectories, will
     * be added to the index. Otherwise, just the directory names are added.
     */
    private static final boolean metaInfFilenames =
        "true".equals(privilegedGetProperty("sun.misc.JarIndex.metaInfFilenames"));

    
Constructs a new, empty jar index.

/**
     * Constructs a new, empty jar index.
     */
    public JarIndex() {
        indexMap = new HashMap<>();
        jarMap = new HashMap<>();
    }

    
Constructs a new index from the specified input stream.

Params:
  • is – the input stream containing the index data
/**
     * Constructs a new index from the specified input stream.
     *
     * @param is the input stream containing the index data
     */
    public JarIndex(InputStream is) throws IOException {
        this();
        read(is);
    }

    
Constructs a new index for the specified list of jar files.

Params:
  • files – the list of jar files to construct the index from.
/**
     * Constructs a new index for the specified list of jar files.
     *
     * @param files the list of jar files to construct the index from.
     */
    public JarIndex(String[] files) throws IOException {
        this();
        this.jarFiles = files;
        parseJars(files);
    }

    
Returns the jar index, or null if none.

Params:
  • jar – the JAR file to get the index from.
Throws:
/**
     * Returns the jar index, or <code>null</code> if none.
     *
     * @param jar the JAR file to get the index from.
     * @exception IOException if an I/O error has occurred.
     */
    public static JarIndex getJarIndex(JarFile jar) throws IOException {
        JarIndex index = null;
        JarEntry e = jar.getJarEntry(INDEX_NAME);
        // if found, then load the index
        if (e != null) {
            index = new JarIndex(jar.getInputStream(e));
        }
        return index;
    }

    
Returns the jar files that are defined in this index.

/**
     * Returns the jar files that are defined in this index.
     */
    public String[] getJarFiles() {
        return jarFiles;
    }

    /*
     * Add the key, value pair to the hashmap, the value will
     * be put in a linked list which is created if necessary.
     */
    private void addToList(String key, String value,
                           HashMap<String,LinkedList<String>> t) {
        LinkedList<String> list = t.get(key);
        if (list == null) {
            list = new LinkedList<>();
            list.add(value);
            t.put(key, list);
        } else if (!list.contains(value)) {
            list.add(value);
        }
    }

    
Returns the list of jar files that are mapped to the file.

Params:
  • fileName – the key of the mapping
/**
     * Returns the list of jar files that are mapped to the file.
     *
     * @param fileName the key of the mapping
     */
    public LinkedList<String> get(String fileName) {
        LinkedList<String> jarFiles = null;
        if ((jarFiles = indexMap.get(fileName)) == null) {
            /* try the package name again */
            int pos;
            if((pos = fileName.lastIndexOf('/')) != -1) {
                jarFiles = indexMap.get(fileName.substring(0, pos));
            }
        }
        return jarFiles;
    }

    
Add the mapping from the specified file to the specified
jar file. If there were no mapping for the package of the
specified file before, a new linked list will be created,
the jar file is added to the list and a new mapping from
the package to the jar file list is added to the hashmap.
Otherwise, the jar file will be added to the end of the
existing list.

Params:
  • fileName – the file name
  • jarName – the jar file that the file is mapped to
/**
     * Add the mapping from the specified file to the specified
     * jar file. If there were no mapping for the package of the
     * specified file before, a new linked list will be created,
     * the jar file is added to the list and a new mapping from
     * the package to the jar file list is added to the hashmap.
     * Otherwise, the jar file will be added to the end of the
     * existing list.
     *
     * @param fileName the file name
     * @param jarName the jar file that the file is mapped to
     *
     */
    public void add(String fileName, String jarName) {
        String packageName;
        int pos;
        if((pos = fileName.lastIndexOf('/')) != -1) {
            packageName = fileName.substring(0, pos);
        } else {
            packageName = fileName;
        }

        addMapping(packageName, jarName);
    }

    
Same as add(String,String) except that it doesn't strip off from the
last index of '/'. It just adds the jarItem (filename or package)
as it is received.

/**
     * Same as add(String,String) except that it doesn't strip off from the
     * last index of '/'. It just adds the jarItem (filename or package)
     * as it is received.
     */
    private void addMapping(String jarItem, String jarName) {
        // add the mapping to indexMap
        addToList(jarItem, jarName, indexMap);

        // add the mapping to jarMap
        addToList(jarName, jarItem, jarMap);
     }

    
Go through all the jar files and construct the
index table.

/**
     * Go through all the jar files and construct the
     * index table.
     */
    private void parseJars(String[] files) throws IOException {
        if (files == null) {
            return;
        }

        String currentJar = null;

        for (int i = 0; i < files.length; i++) {
            currentJar = files[i];
            ZipFile zrf = new ZipFile(currentJar.replace
                                      ('/', File.separatorChar));

            Enumeration<? extends ZipEntry> entries = zrf.entries();
            while(entries.hasMoreElements()) {
                ZipEntry entry = entries.nextElement();
                String fileName = entry.getName();

                // Skip the META-INF directory, the index, and manifest.
                // Any files in META-INF/ will be indexed explicitly
                if (fileName.equals("META-INF/") ||
                    fileName.equals(INDEX_NAME) ||
                    fileName.equals(JarFile.MANIFEST_NAME) ||
                    fileName.startsWith("META-INF/versions/"))
                    continue;

                if (!metaInfFilenames || !fileName.startsWith("META-INF/")) {
                    add(fileName, currentJar);
                } else if (!entry.isDirectory()) {
                        // Add files under META-INF explicitly so that certain
                        // services, like ServiceLoader, etc, can be located
                        // with greater accuracy. Directories can be skipped
                        // since each file will be added explicitly.
                        addMapping(fileName, currentJar);
                }
            }

            zrf.close();
        }
    }

    
Writes the index to the specified OutputStream

Params:
  • out – the output stream
Throws:
/**
     * Writes the index to the specified OutputStream
     *
     * @param out the output stream
     * @exception IOException if an I/O error has occurred
     */
    public void write(OutputStream out) throws IOException {
        BufferedWriter bw = new BufferedWriter
            (new OutputStreamWriter(out, "UTF8"));
        bw.write("JarIndex-Version: 1.0\n\n");

        if (jarFiles != null) {
            for (int i = 0; i < jarFiles.length; i++) {
                /* print out the jar file name */
                String jar = jarFiles[i];
                bw.write(jar + "\n");
                LinkedList<String> jarlist = jarMap.get(jar);
                if (jarlist != null) {
                    Iterator<String> listitr = jarlist.iterator();
                    while(listitr.hasNext()) {
                        bw.write(listitr.next() + "\n");
                    }
                }
                bw.write("\n");
            }
            bw.flush();
        }
    }


    
Reads the index from the specified InputStream.

Params:
  • is – the input stream
Throws:
/**
     * Reads the index from the specified InputStream.
     *
     * @param is the input stream
     * @exception IOException if an I/O error has occurred
     */
    public void read(InputStream is) throws IOException {
        BufferedReader br = new BufferedReader
            (new InputStreamReader(is, "UTF8"));
        String line = null;
        String currentJar = null;

        /* an ordered list of jar file names */
        Vector<String> jars = new Vector<>();

        /* read until we see a .jar line */
        while((line = br.readLine()) != null && !line.endsWith(".jar"));

        for(;line != null; line = br.readLine()) {
            if (line.isEmpty())
                continue;

            if (line.endsWith(".jar")) {
                currentJar = line;
                jars.add(currentJar);
            } else {
                String name = line;
                addMapping(name, currentJar);
            }
        }

        jarFiles = jars.toArray(new String[jars.size()]);
    }

    
Merges the current index into another index, taking into account
the relative path of the current index.

Params:
  • toIndex – The destination index which the current index will
               merge into.
  • path –    The relative path of the this index to the destination
               index.
/**
     * Merges the current index into another index, taking into account
     * the relative path of the current index.
     *
     * @param toIndex The destination index which the current index will
     *                merge into.
     * @param path    The relative path of the this index to the destination
     *                index.
     *
     */
    public void merge(JarIndex toIndex, String path) {
        Iterator<Map.Entry<String,LinkedList<String>>> itr = indexMap.entrySet().iterator();
        while(itr.hasNext()) {
            Map.Entry<String,LinkedList<String>> e = itr.next();
            String packageName = e.getKey();
            LinkedList<String> from_list = e.getValue();
            Iterator<String> listItr = from_list.iterator();
            while(listItr.hasNext()) {
                String jarName = listItr.next();
                if (path != null) {
                    jarName = path.concat(jarName);
                }
                toIndex.addMapping(packageName, jarName);
            }
        }
    }
}