Redis 9.redis的Java客户端Jedis

Redis

@Author:hanguixian
@Email:[email protected]

九 Redis的Java客户端Jedis

  • 使用gradle引入Jredis的jar包
// https://mvnrepository.com/artifact/redis.clients/jedis
    compile group: 'redis.clients', name: 'jedis', version: '3.0.0'
  • java代码
package com.hgx.redis;

import redis.clients.jedis.Jedis;

public class RedisTest {
    public static void main(String[] args) {
        Jedis jedis = new Jedis("127.0.0.1",6379) ;
        String ping  = jedis.ping() ;
        System.out.println("ping result:"+ping);
        jedis.set("k2","v2") ;
        System.out.println(jedis.keys("*"));
        System.out.println("k1:"+jedis.get("k1")+" k2:"+jedis.get("k2"));
    }
}
//ping result:PONG
//[k1, k2]
//k1:v1 k2:v2

1 Jedis常用操作

public class Test02 {
  public static void main(String[] args) {
      
     Jedis jedis = new Jedis("127.0.0.1",6379);
     //key
     Set<String> keys = jedis.keys("*");
     for (Iterator iterator = keys.iterator(); iterator.hasNext();) {
       String key = (String) iterator.next();
       System.out.println(key);
     }
     System.out.println("jedis.exists====>"+jedis.exists("k2"));
     System.out.println(jedis.ttl("k1"));
     //String
     //jedis.append("k1","myreids");
     System.out.println(jedis.get("k1"));
     jedis.set("k4","k4_redis");
     System.out.println("----------------------------------------");
     jedis.mset("str1","v1","str2","v2","str3","v3");
     System.out.println(jedis.mget("str1","str2","str3"));
     //list
     System.out.println("----------------------------------------");
     //jedis.lpush("mylist","v1","v2","v3","v4","v5");
     List<String> list = jedis.lrange("mylist",0,-1);
     for (String element : list) {
       System.out.println(element);
     }
     //set
     jedis.sadd("orders","jd001");
     jedis.sadd("orders","jd002");
     jedis.sadd("orders","jd003");
     Set<String> set1 = jedis.smembers("orders");
     for (Iterator iterator = set1.iterator(); iterator.hasNext();) {
       String string = (String) iterator.next();
       System.out.println(string);
     }
     jedis.srem("orders","jd002");
     System.out.println(jedis.smembers("orders").size());
     //hash
     jedis.hset("hash1","userName","lisi");
     System.out.println(jedis.hget("hash1","userName"));
     Map<String,String> map = new HashMap<String,String>();
     map.put("telphone","13811814763");
     map.put("address","xxxxx");
     map.put("email","[email protected]");
     jedis.hmset("hash2",map);
     List<String> result = jedis.hmget("hash2", "telphone","email");
     for (String element : result) {
       System.out.println(element);
     }
     //zset
     jedis.zadd("zset01",60d,"v1");
     jedis.zadd("zset01",70d,"v2");
     jedis.zadd("zset01",80d,"v3");
     jedis.zadd("zset01",90d,"v4");
     
     Set<String> s1 = jedis.zrange("zset01",0,-1);
     for (Iterator iterator = s1.iterator(); iterator.hasNext();) {
       String string = (String) iterator.next();
       System.out.println(string);
     }     
  }
}

2 事务提交

2.1 日常

public class Test03 {
  public static void main(String[] args) {
     Jedis jedis = new Jedis("127.0.0.1",6379);
     
     //监控key,如果该动了事务就被放弃
     /*3
     jedis.watch("serialNum");
     jedis.set("serialNum","s#####################");
     jedis.unwatch();*/
     
     Transaction transaction = jedis.multi();//被当作一个命令进行执行
     Response<String> response = transaction.get("serialNum");
     transaction.set("serialNum","s002");
     response = transaction.get("serialNum");
     transaction.lpush("list3","a");
     transaction.lpush("list3","b");
     transaction.lpush("list3","c");
     
     transaction.exec();
     //2 transaction.discard();
     System.out.println("serialNum***********"+response.get());   
  }
}

2.2 加锁

public class TestTransaction {

	public boolean transMethod() {
     Jedis jedis = new Jedis("127.0.0.1", 6379);
     int balance;// 可用余额
     int debt;// 欠额
     int amtToSubtract = 10;// 实刷额度


     jedis.watch("balance");
     //jedis.set("balance","5");//此句不该出现,讲课方便。模拟其他程序已经修改了该条目
     balance = Integer.parseInt(jedis.get("balance"));
     if (balance < amtToSubtract) {
       jedis.unwatch();
       System.out.println("modify");
       return false;
     } else {
       System.out.println("***********transaction");
       Transaction transaction = jedis.multi();
       transaction.decrBy("balance", amtToSubtract);
       transaction.incrBy("debt", amtToSubtract);
       transaction.exec();
       balance = Integer.parseInt(jedis.get("balance"));
       debt = Integer.parseInt(jedis.get("debt"));


       System.out.println("*******" + balance);
       System.out.println("*******" + debt);
       return true;
     }
  }


  /**
   * 通俗点讲,watch命令就是标记一个键,如果标记了一个键, 在提交事务前如果该键被别人修改过,那事务就会失败,这种情况通常可以在程序中
   * 重新再尝试一次。
   * 首先标记了键balance,然后检查余额是否足够,不足就取消标记,并不做扣减; 足够的话,就启动事务进行更新操作,
   * 如果在此期间键balance被其它人修改, 那在提交事务(执行exec)时就会报错, 程序中通常可以捕获这类错误再重新执行一次,直到成功。
   */
  public static void main(String[] args) {
     TestTransaction test = new TestTransaction();
     boolean retValue = test.transMethod();
     System.out.println("main retValue-------: " + retValue);
  }
}

3 主从复制

  • 主写从读
//6379,6380启动,先各自先独立
public static void main(String[] args) throws InterruptedException 
  {
     Jedis jedis_M = new Jedis("127.0.0.1",6379);
     Jedis jedis_S = new Jedis("127.0.0.1",6380);
     
     jedis_S.slaveof("127.0.0.1",6379);
     
     jedis_M.set("k6","v6");
     Thread.sleep(500);
     System.out.println(jedis_S.get("k6"));
  }

4 JedisPool

  • 获取Jedis实例需要从JedisPool中获取

  • 用完Jedis实例需要返还给JedisPool

  • 如果Jedis在使用过程中出错,则也需要还给JedisPool

4.1 案例代码

public class JedisPoolUtil {
 //被volatile修饰的变量不会被本地线程缓存,对该变量的读写都是直接操作共享内存。
 private static volatile JedisPool jedisPool = null;
  
  private JedisPoolUtil() {}
  
  public static JedisPool getJedisPoolInstance()
 {
     if(null == jedisPool)
    {
       synchronized (JedisPoolUtil.class)
      {
          if(null == jedisPool)
         {
           JedisPoolConfig poolConfig = new JedisPoolConfig();
           poolConfig.setMaxActive(1000);
           poolConfig.setMaxIdle(32);
           poolConfig.setMaxWait(100*1000);
           poolConfig.setTestOnBorrow(true);
            
            jedisPool = new JedisPool(poolConfig,"127.0.0.1");
         }
      }
    }
     return jedisPool;
 }
  
  public static void release(JedisPool jedisPool,Jedis jedis)
 {
     if(null != jedis)
    {
      jedisPool.returnResourceObject(jedis);
    }
 }
}
public class Test01 {
  public static void main(String[] args) {
     JedisPool jedisPool = JedisPoolUtil.getJedisPoolInstance();
     Jedis jedis = null;
     
     try 
     {
       jedis = jedisPool.getResource();
       jedis.set("k18","v183");
       
     } catch (Exception e) {
       e.printStackTrace();
     }finally{
       JedisPoolUtil.release(jedisPool, jedis);
     }
  }
}

4.2 配置总结

JedisPool的配置参数大部分是由JedisPoolConfig的对应项来赋值的。

  • maxActive:控制一个pool可分配多少个jedis实例,通过pool.getResource()来获取;如果赋值为-1,则表示不限制;如果pool已经分配了maxActive个jedis实例,则此时pool的状态为exhausted。
  • maxIdle:控制一个pool最多有多少个状态为idle(空闲)的jedis实例;
  • whenExhaustedAction:表示当pool中的jedis实例都被allocated完时,pool要采取的操作;默认有三种。
    • WHEN_EXHAUSTED_FAIL --> 表示无jedis实例时,直接抛出NoSuchElementException;
    • WHEN_EXHAUSTED_BLOCK --> 则表示阻塞住,或者达到maxWait时抛出JedisConnectionException
    • WHEN_EXHAUSTED_GROW --> 则表示新建一个jedis实例,也就说设置的maxActive无用;
  • maxWait:表示当borrow一个jedis实例时,最大的等待时间,如果超过等待时间,则直接抛JedisConnectionException;
  • testOnBorrow:获得一个jedis实例的时候是否检查连接可用性(ping());如果为true,则得到的jedis实例均是可用的;
  • testOnReturn:return 一个jedis实例给pool时,是否检查连接可用性(ping());
  • testWhileIdle:如果为true,表示有一个idle object evitor线程对idle object进行扫描,如果validate失败,此object会被从pool中drop掉;这一项只有在timeBetweenEvictionRunsMillis大于0时才有意义;
  • timeBetweenEvictionRunsMillis:表示idle object evitor两次扫描之间要sleep的毫秒数;
  • numTestsPerEvictionRun:表示idle object evitor每次扫描的最多的对象数;
  • minEvictableIdleTimeMillis:表示一个对象至少停留在idle状态的最短时间,然后才能被idle object evitor扫描并驱逐;这一项只有在timeBetweenEvictionRunsMillis大于0时才有意义;
  • softMinEvictableIdleTimeMillis:在minEvictableIdleTimeMillis基础上,加入了至少minIdle个对象已经在pool里面了。如果为-1,evicted不会根据idle time驱逐任何对象。如果minEvictableIdleTimeMillis>0,则此项设置无意义,且只有在timeBetweenEvictionRunsMillis大于0时才有意义;
  • lifo:borrowObject返回对象时,是采用DEFAULT_LIFO(last in first out,即类似cache的最频繁使用队列),如果为False,则表示FIFO队列;

其中JedisPoolConfig对一些参数的默认设置如下

  • testWhileIdle=true
  • minEvictableIdleTimeMills=60000
  • timeBetweenEvictionRunsMillis=30000
  • numTestsPerEvictionRun=-1

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