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JAVA连接REDIS缓存数据库

发表于 分类于

3.2.1 导入JAR包

commons-pool2-2.3.jar
jedis-2.7.0.jar

3.2.2 单实例连接
代码：

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package com.itheima.redis;
 

import redis.clients.jedis.Jedis;

 

/**

 * 演示Jedis对象操作Redis内存数据库

 * 相当于客户端

 */

public class Demo01 {

public static void main(String[] args) {

//NO1)创建Jedis对象

//参数一： 连接装Redis数据库的机器的IP

//参数二：Redis数据库占用的端口号

Jedis jedis = new Jedis(“127.0.0.1”,6379);

//NO2)调用Jedis对象的API操作Redis数据库

//选择15号数据库

jedis.select(15);

//将key=value存入15号数据库

jedis.set(“username”,“赵君”);

//取出key=value

System.out.println(jedis.get(“username”));

//NO3关闭Jedis对象

jedis.close();

}

}

 

package com.itheima.redis;

 

import java.util.List;

import redis.clients.jedis.Jedis;

 

/**

 * 演示Jedis对象操作Redis内存数据库

 * 相当于客户端

 */

public class Demo02 {

public static void main(String[] args) {

//NO1)创建Jedis对象

Jedis jedis = new Jedis(“127.0.0.1”,6379);

//NO2)调用Jedis对象的API操作Redis数据库，默认选择0号数据库

jedis.select(15);

jedis.lpush(“class”,new String[]{“如茶”,“如草”,“如叶”,“如花”});

List<String> list = jedis.lrange(“class”,0,-1);

for(String str : list){

System.out.print(str + ” “);

}

//NO3关闭Jedis对象

jedis.close();

}

}

3.2.3 连接池连接
代码：

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package com.itheima.redis;
 

import redis.clients.jedis.Jedis;

import redis.clients.jedis.JedisPool;

import redis.clients.jedis.JedisPoolConfig;

 

/**

 * 演示Jedis连接池

 * 客户端

 */

public class Demo01 {

public static void main(String[] args) {

//NO1)创建Jedis连接池配置对象，类似到c3p0-config.xml文件

JedisPoolConfig config = new JedisPoolConfig();

//NO2)创建Jedis连接池

//设置连接池最多存入10个Jedis对象

config.setMaxTotal(10);

//从连接池中取出Jedis对象最多等2秒

config.setMaxWaitMillis(2000);

//NO3)从Jedis连接池中取出一个Jedis对象

JedisPool pool = new JedisPool(config,“127.0.0.1”,6379);

//NO4)使用Jedis对象操作Redis数据库

Jedis jedis = pool.getResource();

//选择15号数据库

jedis.select(15);

//根据key找value

String username = jedis.get(“username”);

//如果value找到了

if(username != null){

//删除该key

jedis.del(“username”);

}

//NO5)将Jedis对象还回给Jedis连接池

jedis.close();

}

}

3.2.4 编写JedisUtil工具类
代码：

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package com.itheima.redis.service;
 

import redis.clients.jedis.Jedis;

import com.itheima.redis.util.JedisUtil;

 

/**

 * 演示通过JedisUtils来获取,操作,关闭Jedis对象

 * 客户端

 */

public class Demo01 {

public static void main(String[] args) throws Exception{

//获取Jedis对象

Jedis jedis = JedisUtil.getJedis();

//使用Jedis对象操作Redis数据库

jedis.set(“address”,“长沙”);

//关闭Jedis对象

JedisUtil.close(jedis);

}

}

 

package com.itheima.redis.util;

 

import java.util.ResourceBundle;

import redis.clients.jedis.Jedis;

import redis.clients.jedis.JedisPool;

import redis.clients.jedis.JedisPoolConfig;

 

/**

 * Jedis工具类

 */

public final class JedisUtil {

private static JedisPool pool;

private static String maxTotal;

private static String maxWaitMillis;

private static String host;

private static String port;

/**

 * 读取src/jedis.properties属性文件中的内容

 */

static{

//ResourceBundle专用于去类路径下找*.properties文件，所以扩展名properties可以不写

//建议项目中的配置文件放在src目录下

ResourceBundle rb = ResourceBundle.getBundle(“jedis”);

//根据key找value

maxTotal = rb.getString(“maxTotal”);

maxWaitMillis = rb.getString(“maxWaitMillis”);

host = rb.getString(“host”);

port = rb.getString(“port”);

}

/**

 * 创建连接池对象

 */

static{

JedisPoolConfig config = new JedisPoolConfig();

config.setMaxTotal(Integer.parseInt(maxTotal));

config.setMaxWaitMillis(Integer.parseInt(maxWaitMillis));

pool = new JedisPool(config,host,Integer.parseInt(port));

}

private JedisUtil(){

}

/**

 * 获取Jedis对象

 */

public static Jedis getJedis() throws Exception{

//如果连接池非空

if(pool != null){

//从连接池中获取Jedis对象

return pool.getResource();

}else{

//return null;

//抛异常

throw new Exception(“Jedis不能为空”);

}

}

/**

 * 关闭Jedis对象

 */

public static void close(Jedis jedis) {

if(jedis != null){

jedis.close();

}

}

}

 

jedis.properties

maxTotal=10

maxWaitMillis=2000

host=127.0.0.1

port=6379

目前为止，我们用过的工具类很多了

04 Redis实战之查询所有省份（重点）

代码：

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<%@ page language=“java” import=“java.util.*” pageEncoding=“UTF-8”%>

<!DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN”>

<html>

  <head>

    <title>My JSP ‘index.jsp’ starting page</title>

<meta http-equiv=“pragma” content=“no-cache”>

<meta http-equiv=“cache-control” content=“no-cache”>

<meta http-equiv=“expires” content=“0”>    

<meta http-equiv=“keywords” content=“keyword1,keyword2,keyword3”>

<meta http-equiv=“description” content=“This is my page”>

<!– 引入JQ的JS文件 –>

<script type=“text/javascript” src=“js/jquery-1.11.3.min.js”></script>

  </head>

  <body>

    

    <select id=“provinceID”>

    <option>选择省份</option>

<%–当浏览器加载index.jsp页面时，动态加载省份–%>

    </select>

    

    

    <script type=“text/javascript”>

    //当浏览器加载index.jsp页面时，动态加载省份

    $(function(){

    //发送AJAX请求

    var url = “${pageContext.request.contextPath}/ProvinceServlet”;

    var data = null;

    var callback = function(backData){//[{“pid”:1,”pname”:”湖南”},{“pid”:2,”pname”:”广东”}]

    //用JS语法来解析JSON对象

    for(var i=0;i<backData.length;i++){

    //获取每个JSON对象的pid

    var pid = backData[i].pid;

    //获取每个JSON对象的pname

    var pname = backData[i].pname;

    //创建option标签

    var $option = $(“<option value='” + pid + “‘>” + pname + “</option>”);

    //将option标签添加到select标签中

    $(“#provinceID”).append( $option );

    }//for-end

    };

    var type = “json”;

    $.post(url,data,callback,type);

    });

    </script>

    

  </body>

</html>
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package com.itheima.redis.web;

 

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.itheima.redis.service.ProvinceService;

import com.itheima.redis.util.PrintUtil;

 

/**

 * web层

 */

public class ProvinceServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

}

public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

try {

request.setCharacterEncoding(“UTF-8”);

//创建业务层对象，并调用方法

ProvinceService service = new ProvinceService();

String provinceListJSON = service.findAllProvince();

//用IO形式将JSON字符串输出到客户端

PrintUtil.toClient(provinceListJSON,response);

} catch (Exception e) {

e.printStackTrace();

request.setAttribute(“MESSAGE”,“查询所有省份失败”);

request.getRequestDispatcher(“/WEB-INF/message.jsp”).forward(request,response);

}

}

}

 

package com.itheima.redis.service;

 

import java.util.List;

import redis.clients.jedis.Jedis;

import com.google.gson.Gson;

import com.itheima.redis.dao.ProvinceDao;

import com.itheima.redis.entity.Province;

import com.itheima.redis.util.JedisUtil;

 

/**

 * service层

 */

public class ProvinceService {

private ProvinceDao dao = new ProvinceDao();

/**

 * 查询所有省份

 */

public String findAllProvince() throws Exception{

//获取Jedis对象

Jedis jedis = JedisUtil.getJedis();

//根据key去Redis中找到对应value

String provinceListJSON = jedis.get(“PROVINCE_LIST_JSON”);

//如果key存在

if(provinceListJSON != null){

System.out.println(“去Redis中取”);

//关闭Jedis对象

JedisUtil.close(jedis);

//返回

return provinceListJSON;

//如果key不存在

}else{

System.out.println(“去MySQL中取”);

//调用持久层对象的方法

List<Province> provinceList = dao.findAllProvince();

//为了让以后，少查MySQL，我们将List集合转成JSON字符串

Gson gson = new Gson();

provinceListJSON = gson.toJson(provinceList);

//存入Redis中

jedis.set(“PROVINCE_LIST_JSON”,provinceListJSON);

//关闭Jedis对象

JedisUtil.close(jedis);

//返回

return provinceListJSON;

}

}

}

 

package com.itheima.redis.dao;

 

import java.sql.SQLException;

import java.util.List;

import org.apache.commons.dbutils.QueryRunner;

import org.apache.commons.dbutils.handlers.BeanListHandler;

import com.itheima.redis.entity.Province;

import com.itheima.redis.util.JdbcUtil;

 

/**

 * dao层

 */

public class ProvinceDao {

/**

 * 查询所有的省份

 */

public List<Province> findAllProvince() throws SQLException{

//创建QueryRunner对象

QueryRunner runner = new QueryRunner(JdbcUtil.getDataSource());

//创建SQL语句

String sql = ” SELECT *” +

     ” FROM tab_province” +

     ” ORDER BY pid ASC”;

//创建数组

Object[] params = null;

//执行SQL语句

return runner.query(sql,new BeanListHandler<Province>(Province.class),params);

}

}

 

package com.itheima.redis.entity;

 

/**

 * 省份

 * 与

 * tab_province表一一对应

 */

public class Province implements java.io.Serializable{

private int pid;//编号

private String pname;//名字

public Province(){}

public int getPid() {

return pid;

}

public void setPid(int pid) {

this.pid = pid;

}

public String getPname() {

return pname;

}

public void setPname(String pname) {

this.pname = pname;

}

}

 

package com.itheima.redis.util;

 

import com.mchange.v2.c3p0.ComboPooledDataSource;

 

/**

 * Jdbc工具类

 */

public final class JdbcUtil {

private JdbcUtil(){}

/**

 * 去src/c3p0–config.xml文件

 */

private static ComboPooledDataSource dataSource = new ComboPooledDataSource();

/**

 * 获取DataSource

 */

public static ComboPooledDataSource getDataSource() {

return dataSource;

}

}

 

package com.itheima.redis.util;

 

import java.util.ResourceBundle;

import redis.clients.jedis.Jedis;

import redis.clients.jedis.JedisPool;

import redis.clients.jedis.JedisPoolConfig;

 

/**

 * Jedis工具类

 */

public final class JedisUtil {

private static JedisPool pool;

private static String maxTotal;

private static String maxWaitMillis;

private static String host;

private static String port;

/**

 * 读取src/jedis.properties属性文件中的内容

 */

static{

//ResourceBundle专用于去类路径下找*.properties文件，所以扩展名properties可以不写

//建议项目中的配置文件放在src目录下

ResourceBundle rb = ResourceBundle.getBundle(“jedis”);

//根据key找value

maxTotal = rb.getString(“maxTotal”);

maxWaitMillis = rb.getString(“maxWaitMillis”);

host = rb.getString(“host”);

port = rb.getString(“port”);

}

/**

 * 创建连接池对象

 */

static{

JedisPoolConfig config = new JedisPoolConfig();

config.setMaxTotal(Integer.parseInt(maxTotal));

config.setMaxWaitMillis(Integer.parseInt(maxWaitMillis));

pool = new JedisPool(config,host,Integer.parseInt(port));

}

private JedisUtil(){

}

/**

 * 获取Jedis对象

 */

public static Jedis getJedis() throws Exception{

//如果连接池非空

if(pool != null){

//从连接池中获取Jedis对象

return pool.getResource();

}else{

//return null;

//抛异常

throw new Exception(“Jedis不能为空”);

}

}

/**

 * 关闭Jedis对象

 */

public static void close(Jedis jedis) {

if(jedis != null){

jedis.close();

}

}

}

 

package com.itheima.redis.util;

 

import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;

 

/**

 * 向客户端输出内容

 */

public final class PrintUtil {

private PrintUtil(){}

public static void toClient(String content,HttpServletResponse response) throws Exception{

response.setContentType(“text/html;charset=UTF-8”);

PrintWriter pw = response.getWriter();

pw.write(content);

pw.flush();

pw.close();

}

}