分布式锁-zookeeper-SharedReentrantReadWriteLock基于InterProcessReadWriteLock（四）分布式重入读写共享锁

分布式重入读写共享锁：InterProcessReadWriteLock共享重入读写锁zk分布式锁基础依赖

package com.miku.common.util.lock.zookeeper;

import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.framework.recipes.locks.InterProcessReadWriteLock;

import java.util.concurrent.ConcurrentHashMap;

/**
 * 分布式共享重入读写锁

 * 
1. 互斥: 读写锁保持一对相关的锁，一个用于只读操作，另一个用于写入。只要没有写入者，读取锁可以同时由多个读取者进程保存。写锁是独占的。
 * 
2. 重入（Reentrancy）: 此锁允许读和写以重入锁的形式重新获取读或写锁。在写入线程/进程持有的所有写入锁定被释放之前，不允许非重入式读取器。
 * 另外，写锁可以获取读锁，但是反之亦然。如果读锁试图获得写入锁，它将永远不会成功。
 * 
3. 写锁降级: 锁定降级重入也允许从写入锁定降级到读取锁定，通过获取写入锁定，然后读取锁定，然后释放写入锁定。但是，从读锁升级到写锁是不可能的。
 * 
4. 公平互斥量: 每个客户端将按请求的顺序（从ZK的角度来看）获得互斥量，即每次请求监听上一个节点。
 * 
5. 根据锁类型（zk路径）维持全局唯一实例
 * 
 *
 * @author:panw.
 */
public class SharedReentrantReadWriteLock extends SharedReentrantLock {

    public static ConcurrentHashMap locks = new ConcurrentHashMap<>();
    private final String lockKey = "read-write-lock";
    private final String readLock = "read-lock";
    private final String writeLock = "write-lock";
    // 获取锁超时时间
    private final long time = 5000L;

    /**
     * Shared Reentrant Read Lock

     * 
1. 获取可重入读锁，zk锁路径，路径相同锁相同，默认获取超时时间5000毫秒。
     * 
2. 实现细节{@link com.miku.common.util.lock.zookeeper.SharedReentrantLock#acquire(String, long)}。
     * 
3. 多个客户端读锁共享。
     * 
     *
     * @param var
     * @return  如果获得了读锁，则返回true，否则返回false
     * @throws IllegalStateException    读锁获取失败
     */
    public boolean readLock(String var) {
        try {
            return super.lock(getReadLock(var),time);
        } catch (Exception e) {
            throw new IllegalStateException("获取读锁失败=>" + e);
        }
    }

    public boolean readLock(String var,final long time) {
        InterProcessMutex interProcessMutex = getReadLock(var);
        try {

            return super.lock(getReadLock(var),time);
        } catch (Exception e) {
            throw new IllegalStateException("获取读锁失败=>" + e);
        }
    }

    /**
     * Shared Reentrant Write Lock
     * 
1. 获取可重入写锁，zk锁路径，路径相同锁相同，默认获取超时时间5000毫秒。
     * 
2. 实现细节{@link com.miku.common.util.lock.zookeeper.SharedReentrantLock#acquire(String, long)}。
     * 
3. 写锁独占,多个客户端无法同时获取写锁，写锁可降级为读锁。
     * 
     *
     * @param var
     * @return
     */
    public boolean writeLock(String var) {
        InterProcessMutex interProcessMutex = getWriteLock(var);
        try {
            return super.lock(getWriteLock(var),time);
        } catch (Exception e) {
            throw new IllegalStateException("获取写锁失败=>" + e);
        }
    }

    public boolean writeLock(String var,final long time) {
        InterProcessMutex interProcessMutex = getWriteLock(var);
        try {
            return super.lock(getWriteLock(var),time);
        } catch (Exception e) {
            throw new IllegalStateException("获取写锁失败=>" + e);
        }
    }

    public void readRelease(String var) throws Exception {
        super.unlock(getReadLock(var));
    }

    public void writeRelease(String var) throws Exception {
        super.unlock(getWriteLock(var));
    }

    private InterProcessReadWriteLock getReadWriteLock(String var){
        String key = lockKey + var;
        InterProcessReadWriteLock interProcessReadWriteLock = null;
        if (locks.containsKey(key)){
            interProcessReadWriteLock = (InterProcessReadWriteLock) locks.get(key);
        } else {
            interProcessReadWriteLock = new InterProcessReadWriteLock(curatorFramework,var);
            locks.put(key,interProcessReadWriteLock);
        }
        return interProcessReadWriteLock;
    }

    private InterProcessMutex getReadLock(String var){
        String readLockKey = readLock + var;
        InterProcessMutex interProcessMutex = null;
        if (locks.containsKey(readLockKey)){
            interProcessMutex = (InterProcessMutex) locks.get(readLockKey);
        } else {
            interProcessMutex = getReadWriteLock(var).readLock();
            locks.put(readLockKey,interProcessMutex);
        }
        return interProcessMutex;
    }

    private InterProcessMutex getWriteLock(String var){
        String writeLockKey = writeLock + var;
        InterProcessMutex interProcessMutex = null;
        if (locks.containsKey(writeLockKey)){
            interProcessMutex = (InterProcessMutex) locks.get(writeLockKey);
        } else {
            interProcessMutex = getReadWriteLock(var).writeLock();
            locks.put(writeLockKey,interProcessMutex);
        }
        return interProcessMutex;
    }
}

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分布式锁-基于zookeeper客户端curator实现锁机制（一）锁基础
分布式锁-zookeeper-SharedLock基于InterProcessSemaphoreMutex（二）分布式共享锁
分布式锁-zookeeper-SharedReentrantLock基于InterProcessMutex（三）分布式重入共享锁
分布式锁-zookeeper-SharedReentrantReadWriteLock基于InterProcessReadWriteLock（四）分布式重入读写共享锁