Redis从基础命令到实战之字符串类型

字符串类型是Redis中最基本的数据类型，能存储任何形式的字符串和和二进制数据。本文以代码形式列举常用的操作命令，并在实践部分演示一个简单的商品管理功能，实现了通常使用关系型数据库开发的增改查功能，注意并没有实现删除功能，这将放在后面的列表类型中去实现。

一、常用命令

pom.xml

<dependencies>
    <dependency>
        <groupId>redis.clients</groupId>
        <artifactId>jedis</artifactId>
        <version>2.8.1</version>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.8</version>
    </dependency>
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-lang3</artifactId>
        <version>3.4</version>
    </dependency>
</dependencies>

StringExample.java

import java.util.Iterator;
import java.util.List;
import java.util.Set;

import redis.clients.jedis.Jedis;

public class StringExample {

    public static void main(String[] args) {
        Jedis jedis = JedisProvider.getJedis();
        //清空数据库
        jedis.flushDB();

        String key = "redis_str";
        //判断key是否存在
        boolean exists = jedis.exists(key);
        if (exists) {
            //删除key,返回实际删除的行数
            long l = jedis.del(key);
            print("del " + key + "=" + l);
        }
        //新增key,成功返回 OK
        String result = jedis.set(key, "a string value");
        print("set " + key + "=" + result);
        //读取value长度
        print("strlen(" + key + ")=" + jedis.strlen(key));
        //读取value
        String value = jedis.get(key);
        print("get " + key + "=" + value);

        //设置过期时间为5秒
        jedis.expire(key, 5);
        //查看某个key的剩余生存时间,单位秒,永久生存或者不存在的都返回-1
        Long ttl = jedis.ttl(key);
        print("ttl of " + key + "=" + ttl);
        //移除某个key的生存时间
        jedis.persist(key);
        print("移除生存时间后 ttl of " + key + "=" + jedis.ttl(key));
        //查看key所储存的值的类型
        String type = jedis.type(key);
        print("type of " + key + "=" + type);

        //一次性新增多个key
        jedis.mset("key001", "value001", "key002", "value002", "key003",
                "value003", "key004", "value004");
        print("批量设置key: key001,key002,key003,key004");

        //读取所有key,遍历,判断类型
        System.out.println("读取所有key并筛选string类型");
        Set<String> keys = jedis.keys("*");
        Iterator<String> it = keys.iterator();
        while (it.hasNext()) {
            key = it.next();
            if (jedis.type(key).equals("string"))
                System.out.println("get " + key + "=" + jedis.get(key));
        }
        System.out.println("------------------------------------------------------");
        System.out.println();

        //一次性获取多个key值
        System.out.println("批量读取key: key001,key002,key003,key004");
        List<String> list = jedis.mget("key001", "key002", "key003", "key004");
        for (int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i));
        }
        System.out.println("------------------------------------------------------");
        System.out.println();
        //一次性删除多个key,返回成功删除个数
        Long del = jedis.del(new String[] { "key001", "key002" });
        print("[批量删除]del key001,key002=" + del);

        // 禁止覆盖
        Long setnx = jedis.setnx("key003", "value003_new");
        print("[禁止覆盖]setnx key003 to value003_new=" + setnx + "; value=" + jedis.get("key003"));

        //新增key同时设置有效期(秒)
        result = jedis.setex(key, 3, "setex demo");
        print("setex " + key + "(ttl 3)=" + result + "; value=" + jedis.get(key) + "; ttl=" + jedis.ttl(key));
        try {
            Thread.sleep(4000);
        } catch (InterruptedException e) {
        }
        print("[4秒之后]get " + key + "=" + jedis.get(key));

        //获取原值, 更新为新值一步完成
        key = "key003";
        String former = jedis.getSet(key, "value002-after-getset");
        print("getSet 原值:" + former + "; 新值" + jedis.get(key));

        //incr 自增
        key = "redis_num";
        jedis.del(key);
        long incr = jedis.incr(key);
        print("incr " + key + " = " + incr);
        incr = jedis.incr(key);
        print("incr " + key + " = " + incr);
        incr = jedis.incrBy(key, 100);
        print("incrBy " + key + " 100 = " + incr);
        Long decr = jedis.decrBy(key, 100);
        print("decrBy " + key + " 100 = " + decr);

        jedis.close();
    }

    private static void print(String info) {
        System.out.println(info);
        System.out.println("------------------------------------------------------");
        System.out.println();
    }
}

JedisProvider.java

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

public class JedisProvider {

    private static JedisPool pool;

    public static Jedis getJedis() {
        if(pool == null) {
            JedisPoolConfig config = new JedisPoolConfig();
            config.setMaxTotal(1024);
            config.setMaxIdle(200);
            config.setMaxWaitMillis(1000);
            config.setTestOnBorrow(true);
            config.setTestOnReturn(true);
            pool = new JedisPool(config, "127.0.0.1", 6380);
        }
        return pool.getResource();
    }
}

二、实践练习

StringLession.Java

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.lang3.math.NumberUtils;

import redis.clients.jedis.Jedis;

public class StringLession {

    public static void main(String[] args) {
        StringLession sl = new StringLession();
        sl.clear();

        //添加一批商品
        for(int i = 0; i< 41; i++) {
            Goods goods = new Goods(0, "goods" + String.format("%05d", i), i);
            sl.addGoods(goods);
        }
        //读取商品总数
        System.out.println("商品总数: " + sl.getTotalCount());
        //分页显示
        List<Goods> list = sl.getGoodsList(2, 20);
        System.out.println("第二页商品:");
        for(Goods goods : list) {
            System.out.println(goods);
        }
    }

    private Jedis jedis = null;

    public StringLession() {
        this.jedis = JedisProvider.getJedis();
    }

    /**
     * 获得一个自增主键值
     * @return
     */
    private long getIncrementId() {
        String key = "goods:count";
        return jedis.incr(key);
    }

    /**
     * 添加一个商品
     * @param goods
     * @return
     */
    public boolean addGoods(Goods goods) {
        long id = getIncrementId();
        goods.setId(id);
        String key = "goods:" + id;
        return jedis.set(key, goods.toString()).equals("OK");
    }

    /**
     * 修改商品
     * @param goods
     * @return
     */
    public boolean editGoods(Goods goods) {
        String key = "goods:" + goods.getId();
        if(jedis.exists(key)) {
            return jedis.set(key, goods.toString()).equals("OK");
        }
        return false;
    }

    /**
     * 读取商品总数
     * @return
     */
    public long getTotalCount() {
        String key = "goods:count";
        return NumberUtils.toLong(jedis.get(key));
    }

    /**
     * 读取用于分页的商品列表
     * @param pageIndex 页数
     * @param pageSize 每页显示行数
     * @return
     */
    public List<Goods> getGoodsList(int pageIndex, int pageSize) {
        int totals = (int)getTotalCount();
        int from = (pageIndex - 1) * pageSize;
        if(from < 0) {
            from = 0;
        }
        else if(from > totals) {
            from = (totals / pageSize) * pageSize;
        }
        int to = from + pageSize;
        if(to > totals) {
            to = totals;
        }
        String[] keys = new String[(int)(to - from)];
        for(int i = from; i < to; i++) {
            keys[i - from] = "goods:" + (i + 1);
        }
        List<String> list = jedis.mget(keys);
        List<Goods> goodsList = new ArrayList<>();
        for(String value : list) {
            goodsList.add(Goods.parseJson(value));
        }
        return goodsList;
    }

    public void clear() {
        jedis.flushDB();
    }
}

Goods.java

import com.alibaba.fastjson.JSON;

public class Goods {

    public Goods() {}

    public Goods(long id, String title, float price) {
        super();
        this.id = id;
        this.title = title;
        this.price = price;
    }

    private long id;
    private String title;
    private float price;
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }

    public String toString() {
        return JSON.toJSONString(this);
    }

    public static Goods parseJson(String json) {
        return JSON.parseObject(json, Goods.class);
    }
}