SpringBoot秒杀系统：2.Mybatis连接数据库

男娘i 2023-02-18 01:54 30阅读 0赞

1.  引入包

<dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>1.3.1</version>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>
    
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid</artifactId>
                <version>1.0.29</version>
            </dependency>

1.  配置Mybatis以及druid

# mybatis
    mybatis.type-aliases-package=com.liuyang.seckill.domain
    mybatis.configuration.map-underscore-to-camel-case=true
    mybatis.configuration.default-fetch-size=100
    mybatis.configuration.default-statement-timeout=3000
    #mybatis.mapperLocations = classpath:com/imooc/dao/*.xml
    # druid
    spring.datasource.url=jdbc:mysql://127.0.0.1:3306/seckill?useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true&useSSL=false
    #spring.datasource.url=jdbc:mysql://62.234.89.7:3306/seckill
    spring.datasource.username=root
    spring.datasource.password=root
    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
    spring.datasource.filters=stat
    spring.datasource.maxActive=2
    spring.datasource.initialSize=1
    spring.datasource.maxWait=60000
    spring.datasource.minIdle=1
    spring.datasource.timeBetweenEvictionRunsMillis=60000
    spring.datasource.minEvictableIdleTimeMillis=300000
    #spring.datasource.validationQuery=select 'x'
    spring.datasource.testWhileIdle=true
    spring.datasource.testOnBorrow=false
    spring.datasource.testOnReturn=false
    spring.datasource.poolPreparedStatements=true
    spring.datasource.maxOpenPreparedStatements=20

1.  映射数据库表格式的实体类编写

package com.liuyang.seckill.domain;
    
    public class User {
        
        private int id;
        private String name;
        private int add_time;
    
        public int getId() {
        
            return id;
        }
    
        public int getAdd_time() {
        
            return add_time;
        }
    
        public void setAdd_time(int add_time) {
        
            this.add_time = add_time;
        }
    
        public void setId(int id) {
        
            this.id = id;
        }
    
        public String getName() {
        
            return name;
        }
    
        public void setName(String name) {
        
            this.name = name;
        }
    
    }

1.  Mapper编写（SQL语句映射）

package com.liuyang.seckill.dao;
    import com.liuyang.seckill.domain.User;
    import org.apache.ibatis.annotations.Mapper;
    import org.apache.ibatis.annotations.Param;
    import org.apache.ibatis.annotations.Select;
    import org.springframework.web.bind.annotation.RequestParam;
    
    @Mapper
    public interface UserDao {
        
    
        @Select("select * from user where id = #{id}")
        public User getById(@RequestParam("id")int id);
    
    }

1.  Service编写用于业务中使用数据库  
    （也可以直接在Controller中注入Mapper直接使用）

package com.liuyang.seckill.service;
    
    import com.liuyang.seckill.dao.UserDao;
    import com.liuyang.seckill.domain.User;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    @Service
    public class UserService {
        
    
        @Autowired
        UserDao userDao;
    
    
        public User getById(int id){
        
            return userDao.getById(id);
        }
    
    }

1.  Controller中注入Mapper或者Service实现对外访问

package com.liuyang.seckill.controller;
    
    import com.liuyang.seckill.dao.UserDao;
    import com.liuyang.seckill.domain.User;
    import com.liuyang.seckill.result.Result;
    import com.liuyang.seckill.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    @Controller
    public class UserController {
        
        @Autowired
        UserDao userDao;
        
        @Autowired
        UserService userService;
    
        @ResponseBody
        @GetMapping("/user")
        public Result getById(int id){
        
            return Result.success(userDao.getById(id));
        }
    
        @ResponseBody
        @GetMapping("/user2")
        public Result getById2(int id){
        
            return Result.success(userDao.getById(id));
        }
    }

1.  访问http://localhost:8080/user?id=1  
    正确结果：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0aGlyZG9uZWw_size_16_color_FFFFFF_t_70]

错误结果：Mapper中SQL语句有问题！  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0aGlyZG9uZWw_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0aGlyZG9uZWw_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200615111651159.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0aGlyZG9uZWw=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0aGlyZG9uZWw_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200615111456561.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0aGlyZG9uZWw=,size_16,color_FFFFFF,t_70