jarreader.java

有关j2me的很好的例子可以研究一下

/**
 *
 * @(#)JarReader.java	1.4 01/03/29
 *
 * Copyright 2001 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 */

package com.sun.midp.midletsuite;

import java.lang.String;

import java.io.IOException;

import com.sun.midp.security.SecurityDomain;
import com.sun.midp.security.Actions;

import com.sun.midp.io.j2me.storage.File;

/**
 * This class provides a Java API for reading an entry from a Jar file stored
 * on the file system.
 */

class JarReader {
    /**
     * Returns the content of the given entry in the JAR file on the
     * file system given by jarFilePath.
     *
     * @param securityDomain domain with permision to install software
     * @param jarFilePath file pathname of the JAR file to read. May
     *          be a relative pathname.
     * @param entryName name of the entry to return.
     *
     * @return the content of the given entry in a byte array.
     * @exception IOException if the entry does not exist.
     * @exception SecurityException if the caller does not have permission
     *   to install software.
     */
    static byte[] readJarEntry(SecurityDomain securityDomain,
                               String jarFilePath, String entryName)
            throws IOException {
        byte[] asciiFilename;
        byte[] asciiEntryName;

        securityDomain.checkIfPermitted(Actions.LIFECYCLE_MANAGEMENT);

        
        asciiFilename = File.toCString(jarFilePath);
        asciiEntryName = File.toCString(entryName);
        return readJarEntry0(asciiFilename, asciiEntryName);
    }

    /**
     * Performs the same function as readJarEntry, except file names
     * are passed in localized characters (so that unicode -> "C" string
     * conversion does not need to happen inside native code).
     *
     * @param localJarFilePath file pathname of the JAR file to read. May
     *          be a relative pathname.
     * @param localEntryName name of the entry to return.
     *
     * @return the content of the given entry in a byte array.
     * @exception IOException if the entry does not exist.
     */
    private static native byte[] readJarEntry0(byte[] localJarFilePath, 
                                       byte[] localEntryName)
        throws IOException;
}