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Jedis的基本使用

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  • Post category:其他




前言

Redis在Java’中的客户端在GitHub上start最高的是Jedis和Redisson。Jedis提供了完整的Redis命令，而Redisson有更多分布式的容器实现



如何使用Jedis



1.导入依赖

首先通过Maven引入Jedis的依赖 

<dependency>
   <groupId>redis.clients</groupId>
   <artifactId>jedis</artifactId>
   <version>2.8.0</version>
</dependency>


2.创建Jedis对象
	Jedis jedis = new Jedis("localhost", 6379);
	jedis.set("singleJedis", "hello jedis!");
	System.out.println(jedis.get("singleJedis"));
	jedis.close();


Jedis对象不是线程安全的，在多线程下使用同一个Jedis对象会出现并发问题，为了避免每次使用Jedis对象时都需要重新创建，Jedis提供了JedisPool。Jedis是线程安全的连接池



3.配置属性文件
#redis config start
redis.ip=127.0.0.1
redis.port=6379

#最大连接数
redis.max.total=20

#最大空闲数
redis.max.idle=10

#最小空闲数
redis.min.idle=2

#从jedis连接池获取连接时，校验并返回可用的连接
redis.test.borrow=true

#把连接放回jedis连接池时，校验并返回可用的连接
redis.test.return=true


4.JedisPool
public class RedisPool {
    private static JedisPool pool;//jedis连接池
    private static Integer maxTotal = Integer.parseInt(PropertiesUtil.getProperty("redis.max.total","20")); //最大连接数
    private static Integer maxIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.max.idle","20"));//在jedispool中最大的idle状态(空闲的)的jedis实例的个数
    private static Integer minIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.min.idle","20"));//在jedispool中最小的idle状态(空闲的)的jedis实例的个数

    private static Boolean testOnBorrow = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.borrow","true"));//在borrow一个jedis实例的时候，是否要进行验证操作，如果赋值true。则得到的jedis实例肯定是可以用的。
    private static Boolean testOnReturn = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.return","true"));//在return一个jedis实例的时候，是否要进行验证操作，如果赋值true。则放回jedispool的jedis实例肯定是可以用的。

    private static String redisIp = PropertiesUtil.getProperty("redis.ip");
    private static Integer redisPort = Integer.parseInt(PropertiesUtil.getProperty("redis.port"));


    private static void initPool(){
        JedisPoolConfig config = new JedisPoolConfig();
        config.setMaxTotal(maxTotal);
        config.setMaxIdle(maxIdle);
        config.setMinIdle(minIdle);

        config.setTestOnBorrow(testOnBorrow);
        config.setTestOnReturn(testOnReturn);

        config.setBlockWhenExhausted(true);//连接耗尽的时候，是否阻塞，false会抛出异常，true阻塞直到超时。默认为true。

        pool = new JedisPool(config,redisIp,redisPort,1000*2);
    }
	
	//静态代码块，初始化Redis池
    static{
        initPool();
    }

    public static Jedis getJedis(){
        return pool.getResource();
    }


    public static void returnBrokenResource(Jedis jedis){
        pool.returnBrokenResource(jedis);
    }

    public static void returnResource(Jedis jedis){
        pool.returnResource(jedis);
    }

}


5.封装Jedis
@Slf4j
public class RedisPoolUtil {


    /**
     * 设置key的有效期，单位是秒
     * @param key
     * @param exTime
     * @return
     */
    public static Long expire(String key,int exTime){
        Jedis jedis = null;
        Long result = null;
        try {
        	//从Redis连接池中获得Jedis对象
            jedis = RedisPool.getJedis();
            //设置成功则返回Jedis对象
            result = jedis.expire(key,exTime);
        } catch (Exception e) {
            log.error("expire key:{} error",key,e);
            RedisPool.returnBrokenResource(jedis);
            return result;
        }
        RedisPool.returnResource(jedis);
        return result;
    }

    //exTime的单位是秒
    //设置key-value并且设置超时时间
    public static String setEx(String key,String value,int exTime){
        Jedis jedis = null;
        String result = null;
        try {
            jedis = RedisPool.getJedis();
            result = jedis.setex(key,exTime,value);
        } catch (Exception e) {
            log.error("setex key:{} value:{} error",key,value,e);
            RedisPool.returnBrokenResource(jedis);
            return result;
        }
        RedisPool.returnResource(jedis);
        return result;
    }

    public static String set(String key,String value){
        Jedis jedis = null;
        String result = null;

        try {
            jedis = RedisPool.getJedis();
            result = jedis.set(key,value);
        } catch (Exception e) {
            log.error("set key:{} value:{} error",key,value,e);
            RedisPool.returnBrokenResource(jedis);
            return result;
        }
        RedisPool.returnResource(jedis);
        return result;
    }

    public static String get(String key){
        Jedis jedis = null;
        String result = null;
        try {
            jedis = RedisPool.getJedis();
            result = jedis.get(key);
        } catch (Exception e) {
            log.error("get key:{} error",key,e);
            RedisPool.returnBrokenResource(jedis);
            return result;
        }
        RedisPool.returnResource(jedis);
        return result;
    }

    public static Long del(String key){
        Jedis jedis = null;
        Long result = null;
        try {
            jedis = RedisPool.getJedis();
            result = jedis.del(key);
        } catch (Exception e) {
            log.error("del key:{} error",key,e);
            RedisPool.returnBrokenResource(jedis);
            return result;
        }
        RedisPool.returnResource(jedis);
        return result;
    }



SharedJedis

为了提高应用的性能，我们通常不止使用一台Redis做缓存服务，而在Redis2.x版本中并没有支持集群，Redis从3.x版本才开始支持集群。Redis2.x版本下实现Redis服务器的扩展需要通过横向扩展的方式，即多个相互独立的主从服务器群，

使用SharedJedis实现分布式缓存，SharedJedis通过一致性哈希来实现分布式缓存，即实现一定的策略将不同的key分配到不同的Redis Server上，达到横向扩展的目的



1.RedisSharedPool
public class RedisShardedPool {
    private static ShardedJedisPool pool;//sharded jedis连接池
    private static Integer maxTotal = Integer.parseInt(PropertiesUtil.getProperty("redis.max.total","20")); //最大连接数
    private static Integer maxIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.max.idle","20"));//在jedispool中最大的idle状态(空闲的)的jedis实例的个数
    private static Integer minIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.min.idle","20"));//在jedispool中最小的idle状态(空闲的)的jedis实例的个数

    private static Boolean testOnBorrow = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.borrow","true"));//在borrow一个jedis实例的时候，是否要进行验证操作，如果赋值true。则得到的jedis实例肯定是可以用的。
    private static Boolean testOnReturn = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.return","true"));//在return一个jedis实例的时候，是否要进行验证操作，如果赋值true。则放回jedispool的jedis实例肯定是可以用的。
	
	//获取Redis1相关信息
    private static String redis1Ip = PropertiesUtil.getProperty("redis1.ip");
    private static Integer redis1Port = Integer.parseInt(PropertiesUtil.getProperty("redis1.port"));
    //获取Redis2的相关信息
    private static String redis2Ip = PropertiesUtil.getProperty("redis2.ip");
    private static Integer redis2Port = Integer.parseInt(PropertiesUtil.getProperty("redis2.port"));




    private static void initPool(){
        JedisPoolConfig config = new JedisPoolConfig();

        config.setMaxTotal(maxTotal);
        config.setMaxIdle(maxIdle);
        config.setMinIdle(minIdle);

        config.setTestOnBorrow(testOnBorrow);
        config.setTestOnReturn(testOnReturn);

        config.setBlockWhenExhausted(true);//连接耗尽的时候，是否阻塞，false会抛出异常，true阻塞直到超时。默认为true。

        JedisShardInfo info1 = new JedisShardInfo(redis1Ip,redis1Port,1000*2);

        JedisShardInfo info2 = new JedisShardInfo(redis2Ip,redis2Port,1000*2);

		//创建一个JedisList
        List<JedisShardInfo> jedisShardInfoList = new ArrayList<JedisShardInfo>(2);

        jedisShardInfoList.add(info1);
        jedisShardInfoList.add(info2);
		
		//RedisSharedPool传入JedisList
        pool = new ShardedJedisPool(config,jedisShardInfoList, Hashing.MURMUR_HASH, Sharded.DEFAULT_KEY_TAG_PATTERN);
    }

    static{
        initPool();
    }

    public static ShardedJedis getJedis(){
        return pool.getResource();
    }


    public static void returnBrokenResource(ShardedJedis jedis){
        pool.returnBrokenResource(jedis);
    }



    public static void returnResource(ShardedJedis jedis){
        pool.returnResource(jedis);
    }

}


2.封装ShraedJedis
@Slf4j
public class RedisShardedPoolUtil {

    /**
     * 设置key的有效期，单位是秒
     * @param key
     * @param exTime
     * @return
     */
    public static Long expire(String key,int exTime){
        ShardedJedis jedis = null;
        Long result = null;
        try {
        	//根据SharedJedis的一致性哈希策略从对应的Redis Server获取值或设置值
            jedis = RedisShardedPool.getJedis();
            result = jedis.expire(key,exTime);
        } catch (Exception e) {
            log.error("expire key:{} error",key,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }

    //exTime的单位是秒
    public static String setEx(String key,String value,int exTime){
        ShardedJedis jedis = null;
        String result = null;
        try {
            jedis = RedisShardedPool.getJedis();
            result = jedis.setex(key,exTime,value);
        } catch (Exception e) {
            log.error("setex key:{} value:{} error",key,value,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }

    public static String set(String key,String value){
        ShardedJedis jedis = null;
        String result = null;

        try {
            jedis = RedisShardedPool.getJedis();
            result = jedis.set(key,value);
        } catch (Exception e) {
            log.error("set key:{} value:{} error",key,value,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }

    public static String getSet(String key,String value){
        ShardedJedis jedis = null;
        String result = null;

        try {
            jedis = RedisShardedPool.getJedis();
            result = jedis.getSet(key,value);
        } catch (Exception e) {
            log.error("getset key:{} value:{} error",key,value,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }

    public static String get(String key){
        ShardedJedis jedis = null;
        String result = null;
        try {
            jedis = RedisShardedPool.getJedis();
            result = jedis.get(key);
        } catch (Exception e) {
            log.error("get key:{} error",key,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }

    public static Long del(String key){
        ShardedJedis jedis = null;
        Long result = null;
        try {
            jedis = RedisShardedPool.getJedis();
            result = jedis.del(key);
        } catch (Exception e) {
            log.error("del key:{} error",key,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }

    public static Long setnx(String key,String value){
        ShardedJedis jedis = null;
        Long result = null;

        try {
            jedis = RedisShardedPool.getJedis();
            result = jedis.setnx(key,value);
        } catch (Exception e) {
            log.error("setnx key:{} value:{} error",key,value,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }
}


除了初始化SharedJedisPool时需要加入多个Redis服务器信息外，其他和Jedis差不多



Shared一致性哈希实现

shared一致性哈希实现采用以下方案：

Redis服务器节点划分：将每台服务器节点采用hash算法划分为160个虚拟节点(可以配置划分权重)

  1. 将划分的虚拟节点采用TreeMap存储
  2. 对每个Redis服务器的物理连接采用LinkedHashMap存储
  3. 对Key or KeyTag 采用同样的hash算法，然后从TreeMap获取大于等于键hash值得节点，取最邻近节点存储；当key的hash值大于虚拟节点hash值得最大值时，存入第一个虚拟节点


sharded采用的hash算法：MD5 和 MurmurHash两种；默认采用64位的MurmurHash算法；MurmurHash是一种高效，低碰撞的hash算法


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