package cn.guagua.mobile.common;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.apache.log4j.Logger;

import cn.guagua.mobile.cache.redis.Redis;

/**
 * 读写锁控制强制读取缓存同步
 * @author shma
 * @date 2014-10-11 15:04:28
 */
public class SynchCacheLock<T> {

    private static final Logger logger = Logger.getLogger(SynchCacheLock.class);
    
    private static Redis.RedisClient redis1 = new Redis.RedisClient("1");
    
    private ReadWriteLock lock = null;
    private Lock readLock = null; // 读锁
    private Lock writeLock = null; // 写锁
    
    public SynchCacheLock() {
        lock = new ReentrantReadWriteLock();
        readLock = lock.readLock();
        writeLock = lock.writeLock();
        System.out.println(Thread.currentThread().getName() + ">>> cache lock init...");
    }
    
    public T getCache(String key, Runnable task) {
        T obj = null;
        readLock.lock();
        try {
            obj = (T) redis1.getObject(key);
            if(obj == null) {
                System.out.println(Thread.currentThread().getName() + " read request " + key + " is null, wait query...");
                readLock.unlock();
                writeLock.lock();
                try {
                    obj = (T) redis1.getObject(key);
                    if(obj == null) {
                        task.run();//强制执行执行写缓存任务
                        System.out.println(Thread.currentThread().getName() + " read request " + key + " end...");
                        obj = (T) redis1.getObject(key);
                    }
                } catch(Throwable e) {
                    System.out.println("readLock error...");
                    e.printStackTrace();
                } finally {
                    readLock.lock();
                    writeLock.unlock();
                }
            }
            System.out.println(Thread.currentThread().getName() + " read request " + key + " data...");
        } catch(Throwable e) {
            System.out.println("lock error...");
            e.printStackTrace();
        } finally {
            readLock.unlock();
        }

        return obj;
    }
}