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Tomcat example source code file (Lock.java)

This example Tomcat source code file (Lock.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

apr_lock_default, apr_lock_flock, apr_lock_proc_pthread, error, error, lock, posix, posix, semaphores, string, string, system, system, use

The Tomcat Lock.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.apache.tomcat.jni;

/** Lock
 *
 * @author Mladen Turk
 * @version $Revision: 467222 $, $Date: 2006-10-24 05:17:11 +0200 (mar., 24 oct. 2006) $
 */

public class Lock {

    /**
     * Enumerated potential types for APR process locking methods
     * <br />Warning : Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
     *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
     */

    public static final int APR_LOCK_FCNTL        = 0; /** fcntl() */
    public static final int APR_LOCK_FLOCK        = 1; /** flock() */
    public static final int APR_LOCK_SYSVSEM      = 2; /** System V Semaphores */
    public static final int APR_LOCK_PROC_PTHREAD = 3; /** POSIX pthread process-based locking */
    public static final int APR_LOCK_POSIXSEM     = 4; /** POSIX semaphore process-based locking */
    public static final int APR_LOCK_DEFAULT      = 5; /** Use the default process lock */

    /**
     * Create and initialize a mutex that can be used to synchronize processes.
     * <br />Warning : Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
     *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
     * @param fname A file name to use if the lock mechanism requires one.  This
     *        argument should always be provided.  The lock code itself will
     *        determine if it should be used.
     * @param mech The mechanism to use for the interprocess lock, if any; one of
     * <PRE>
     *            APR_LOCK_FCNTL
     *            APR_LOCK_FLOCK
     *            APR_LOCK_SYSVSEM
     *            APR_LOCK_POSIXSEM
     *            APR_LOCK_PROC_PTHREAD
     *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
     * </PRE>
     * @param pool the pool from which to allocate the mutex.
     * @return Newly created mutex.
     */
    public static native long create(String fname, int mech, long pool)
        throws Error;

    /**
     * Re-open a mutex in a child process.
     * This function must be called to maintain portability, even
     * if the underlying lock mechanism does not require it.
     * @param fname A file name to use if the mutex mechanism requires one.  This
     *              argument should always be provided.  The mutex code itself will
     *              determine if it should be used.  This filename should be the
     *              same one that was passed to apr_proc_mutex_create().
     * @param pool The pool to operate on.
     * @return Newly opened mutex.
     */
    public static native long childInit(String fname, long pool)
        throws Error;

    /**
     * Acquire the lock for the given mutex. If the mutex is already locked,
     * the current thread will be put to sleep until the lock becomes available.
     * @param mutex the mutex on which to acquire the lock.
     */
    public static native int lock(long mutex);

    /**
     * Attempt to acquire the lock for the given mutex. If the mutex has already
     * been acquired, the call returns immediately with APR_EBUSY. Note: it
     * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
     * if the return value was APR_EBUSY, for portability reasons.
     * @param mutex the mutex on which to attempt the lock acquiring.
     */
    public static native int trylock(long mutex);

    /**
     * Release the lock for the given mutex.
     * @param mutex the mutex from which to release the lock.
     */
    public static native int unlock(long mutex);

    /**
     * Destroy the mutex and free the memory associated with the lock.
     * @param mutex the mutex to destroy.
     */
    public static native int destroy(long mutex);

    /**
     * Return the name of the lockfile for the mutex, or NULL
     * if the mutex doesn't use a lock file
     */
    public static native String lockfile(long mutex);

    /**
     * Display the name of the mutex, as it relates to the actual method used.
     * This matches the valid options for Apache's AcceptMutex directive
     * @param mutex the name of the mutex
     */
    public static native String name(long mutex);

    /**
     * Display the name of the default mutex: APR_LOCK_DEFAULT
     */
    public static native String defname();

}

Other Tomcat examples (source code examples)

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