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 OKString result = jedis.set(key, "a string value");print("set " + key + "=" + result);//读取value长度print("strlen(" + key + ")=" + jedis.strlen(key));//读取valueString 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-1Long 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keyjedis.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);}}

源码下载

Redis从基础命令到实战之散列类型(Hash)
Redis从基础命令到实战之列表类型(List)
Redis从基础命令到实战之集合类型(Set)
Redis从基础命令到实战之有序集合类型(SortedSet)