《Redis应用实例》Java实现（10）：资源池

原书第10章。

package com.foxbill.redisinaction;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.Pipeline;
import redis.clients.jedis.Response;
import redis.clients.jedis.Transaction;
import redis.clients.jedis.exceptions.JedisException;
import java.util.List;

/**
 * 资源池
 */
public class Chapter10 {

    String poolName;
    String keyAvailableResourcePool="resourcePool:available";
    String keyUsedResourcePool="resourcePool:used";

    public Chapter10(String poolName){
        this.poolName = poolName;
        this.keyAvailableResourcePool=String.format("%s:%s", keyAvailableResourcePool,poolName);
        this.keyUsedResourcePool=String.format("%s:%s", keyUsedResourcePool,poolName);
    }

    public void start(Jedis jedis) {
        try{
            for(int i=1;i<=10;i++){
                addResource(jedis,"worker"+i);
            }
            Thread.sleep(1000);
            String resource = useResource(jedis);
            System.out.println("resource:"+resource);
            Thread.sleep(1000);
            resource = useResource(jedis);
            System.out.println("resource:"+resource);
            Thread.sleep(1000);
            resource = useResource(jedis);
            System.out.println("resource:"+resource);
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    private boolean addResource(Jedis jedis,String resourceName) {
        //resource is existed
        if(jedis.sismember(keyAvailableResourcePool,resourceName)){
            return false;
        }
        jedis.sadd(keyAvailableResourcePool,resourceName);
        return true;
    }

    private String useResource(Jedis jedis) {
        try {
            // 1. WATCH 监控键
            jedis.watch(keyAvailableResourcePool);
            // 2. 检查资源池是否为空
            String resource = jedis.srandmember(keyAvailableResourcePool);
            if (resource == null) {
                jedis.unwatch();
                return null;
            }
            // 3. 开启事务并执行移动操作
            Transaction ctx = jedis.multi();
            ctx.smove(keyAvailableResourcePool, keyUsedResourcePool, resource);
            List<Object> results = ctx.exec();

            // 4. 检查事务是否成功
            if (results == null) {
                System.out.println("事务失败：资源池被修改");
                return null;
            }
            return resource;

        } catch (JedisException e) {
            System.err.println("Redis 操作异常: " + e.getMessage());
            return null;
        }
    }
}