redis学习(案例)

Posted 2020-11-29 食惯嘴第一才子

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效果如下

注意：必须要开启redis服务器端

数据库

CREATE DATABASE heima; -- 创建数据库
USE heima; -- 使用数据库
CREATE TABLE province( -- 创建表
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20) NOT NULL

);
-- 插入数据
INSERT INTO province VALUES(NULL,\'北京\');
INSERT INTO province VALUES(NULL,\'上海\');
INSERT INTO province VALUES(NULL,\'广州\');
INSERT INTO province VALUES(NULL,\'陕西\');

jar包

jedis.properties

host=127.0.0.1
port=6379
maxTotal=50
maxIdle=10

js包

加入redis缓存

目录结构

html网页

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>redis缓存+json</title>
    <script src="js/jquery-3.3.1.min.js"></script>
    <script>
        $(function () {
            //发送ajax请求，加载所有省份数据
            $.get("provinceServlet",{},function (data) {
                //json[{"id":1,"name":"北京"},{"id":2,"name":"上海"},{"id":3,"name":"广州"},{"id":4,"name":"陕西"}]

                /*
                    1.获取select
                    2.遍历json数组
                    3.创建<option>
                    4.调用select的append追加option
                 */
                //1.获取select
                var province=$("#province");
                //2.遍历json数组
                $(data).each(function () {
                   // 3.创建<option>
                    var option="<option id=\'"+this.id+"\'>"+this.name+"</option>";
                    //4.调用select的append追加option
                    province.append(option);
                });
            });
        });
    </script>
</head>
<body>
    <select id="province">
        <option>---请选择省份---</option>
    </select>
</body>
</html>

Servlet类

@WebServlet("/provinceServlet")
public class ProvinceServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /*
            1.调用service查询
            2.序列化（写）list为json
            3.响应结果
         */
//        //1.调用service查询
//        ProvinceService service=new ProvinceServiceImpl();
//        List<Province> list = service.findAll();
//        //2.序列化（写）list为json
//        ObjectMapper mapper=new ObjectMapper();
//        String json = mapper.writeValueAsString(list);
        //1.调用service查询
        ProvinceService service=new ProvinceServiceImpl();
        String json = service.findAllJson();

        //System.out.println("json"+json);
        //json[{"id":1,"name":"北京"},{"id":2,"name":"上海"},{"id":3,"name":"广州"},{"id":4,"name":"陕西"}]

        //3.响应结果
        response.setContentType("application/json;charset=utf-8");
        response.getWriter().write(json);




    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

Javabean

public class Province {
    private int id;
    private String name;

    public Province() {
    }

    public Province(int id, String name) {
        this.id = id;
        this.name = name;
    }

    @Override
    public String toString() {
        return "Province{" +
                "id=" + id +
                ", name=\'" + name + \'\\\'\' +
                \'}\';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

dao

public interface ProvinceDao {
    public List<Province> findAll();
}

dao Impl

public class ProvinceDaoImpl implements ProvinceDao {
    private JdbcTemplate template=new JdbcTemplate(JDBCUtil.getDataSource());
    @Override
    public List<Province> findAll() {
        String sql="select * from province";
        List<Province> list = template.query(sql, new BeanPropertyRowMapper<Province>(Province.class));
        return list;
    }
}

service

public interface ProvinceService {
    public List<Province> findAll();
    //redis缓存
    public String findAllJson();
}

sevice Impl(核心)

public class ProvinceServiceImpl implements ProvinceService {
    private ProvinceDao provinceDao=new ProvinceDaoImpl();
    @Override
    public List<Province> findAll() {
        return provinceDao.findAll();
    }

    /*
        使用redis缓存
     */
    @Override
    public String findAllJson() {
        //1.先从redis中查询数据
        //1.1获取redis客户端连接
        Jedis jedis = JedisUtil.getJedis();
        String province_json = jedis.get("province");
        //2判断province是否为空
        if (province_json==null||province_json.length()==0){
            System.out.println("redis没有数据  ---  查询数据库");
            //2.1province为空,也就是redis没有数据  ---  查询数据库
            List<Province> ps = provinceDao.findAll();
            //2.2将ps 序列化为json，也就是写
            ObjectMapper mapper=new ObjectMapper();
            try {
                province_json = mapper.writeValueAsString(ps);
            } catch (JsonProcessingException e) {
                e.printStackTrace();
            }
            //2.3  (不要忘记)将json数据存入到redis中
            jedis.set("province",province_json);
            //3.归还连接
            jedis.close();
        }else {
            System.out.println("redis有数据   ----   查询redis缓存");
            //province不为空，也就是redis有数据   ----   查询redis缓存
        }
        return province_json;
    }
}

工具类

JDBCUtil

public class JDBCUtil {
    private static DataSource ds;
    static {
        //读取配置文件
        InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("druid.properties");
        //创建Properties对象
        Properties pro =new Properties();
        try {
            //获取关联
            pro.load(is);
            //2.初始化druid数据库连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
    public static DataSource getDataSource(){
        return ds;
    }
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
    //释放资源
    public void close(Connection conn, PreparedStatement ps){
        if (ps!=null){
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    //释放资源
    public void close(Connection conn, PreparedStatement ps, ResultSet rs){
        close(conn,ps);
        if (rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

JedisUtil

public class JedisUtil {
    //工具类主要都是获取Jedis
    private static JedisPool jedisPool;
    static {
        //读取配置文件
        InputStream is = JedisUtil.class.getClassLoader().getResourceAsStream("jedis.properties");
        //创建Properties对象
        Properties pro=new Properties();
        //关联文件
        try {
            pro.load(is);
        } catch (Exception e) {
            e.printStackTrace();
        }
        JedisPoolConfig config=new JedisPoolConfig();
        config.setMaxTotal(Integer.parseInt(pro.getProperty("maxTotal")));
        config.setMaxIdle(Integer.parseInt(pro.getProperty("maxIdle")));
        jedisPool=new JedisPool(pro.getProperty("host"),Integer.parseInt(pro.getProperty("port")));
    }
    public static Jedis getJedis(){
        return jedisPool.getResource();
    }
}

druid.properties配置文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/heima?useUnicode=true&characterEncoding=utf8&useSSL=false&serverTimezone=Asia/Shanghai
username=root
password=

# 初始化连接数量
initialSize=5
# 最大连接数
maxActive=10
# 最大等待时间
maxWait=3000

jedis.properties配置文件

host=127.0.0.1
port=6379
maxTotal=50
maxIdle=10

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