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.javaimport 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.javaimport 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
