MyBatisPlus入门案例

MyBatisPlus入门案例

• 准备数据库表

• 新建一个springboot工程

• 导包

  <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
  </dependency>
  
  <dependency>
      <groupId>com.baomidou</groupId>
      <artifactId>mybatis-plus-boot-starter</artifactId>
      <version>3.4.0</version>
  </dependency>
  
   <!-- https://mvnrepository.com/artifact/com.baomidou/mybatis-plus-generator -->
  <dependency>
      <groupId>com.baomidou</groupId>
      <artifactId>mybatis-plus-generator</artifactId>
      <version>3.4.0</version>
  </dependency>
  <!-- 模板引擎 -->
  <dependency>
      <groupId>org.apache.velocity</groupId>
      <artifactId>velocity-engine-core</artifactId>
      <version>2.0</version>
  </dependency>
  
  <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.11</version>
  </dependency>
  

注意：引入 MyBatis-Plus之后请不要再次引入MyBatis以及MyBatis-Spring，以避免因版本差异导致的问题

• 在application.yml配置文件中添加数据库的相关配置：

  # 配置数据库
  spring:
    datasource:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/mybatis_plus?characterEncoding=utf8&serverTimezone=GMT%2B8
      username: root
      password: 123456
  # 配置日志
  mybatis-plus:
    configuration:
      log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  

• 在 Spring Boot 启动类中添加@MapperScan注解，扫描 Mapper 文件夹

  package com.yl;
  
  import org.mybatis.spring.annotation.MapperScan;
  import org.springframework.boot.SpringApplication;
  import org.springframework.boot.autoconfigure.SpringBootApplication;
  
  @SpringBootApplication
  @MapperScan("com.yl.mapper")//扫描mapper类
  public class MybatisPlus01Application {
  
      public static void main(String[] args) {
          SpringApplication.run(MybatisPlus01Application.class, args);
      }
  
  }
  

• 实体类

  package com.yl.bean;
  
  import lombok.Data;
  import lombok.NoArgsConstructor;
  
  import java.io.Serializable;
  
  /**
   * 用户实体类
   */
  @Data
  @NoArgsConstructor
  public class User implements Serializable {
      private Integer id;
      private String name;
      private Integer age;
      private String email;
  }
  

• Mapper类

  package com.yl.mapper;
  
  import com.baomidou.mybatisplus.core.mapper.BaseMapper;
  import com.yl.bean.User;
  import org.springframework.stereotype.Repository;
  
  /**
   * 用户映射接口
   */
  @Repository
  public interface UserMapper extends BaseMapper<User> {
  
  }
  

• 测试类

  package com.yl.mybatis_plus_01;
  
  import com.yl.bean.User;
  import com.yl.mapper.UserMapper;
  import org.junit.jupiter.api.Test;
  import org.junit.runner.RunWith;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.boot.test.context.SpringBootTest;
  import org.springframework.test.context.junit4.SpringRunner;
  
  import java.util.List;
  
  @SpringBootTest
  @RunWith(SpringRunner.class)
  class MybatisPlus01ApplicationTests {
      @Autowired
      private UserMapper userMapper;
  
      /**
       *查询所有
       */
      @Test
      void contextLoads() {
          List<User> userList=userMapper.selectList(null);
  
          userList.forEach(System.out::println);
    }
  
      /**
       * 添加用户
       */
      @Test
      void add(){
          User user=new User();
          user.setId(6);
          user.setAge(17);
          user.setName("yl01");
          user.setEmail("123@qq.com");
  
          userMapper.insert(user);
      }
  
      /**
       * 根据id修改用户
       * mybatisplus的修改sql语句是动态sql，没有修改的字段会保留原来的值
       */
      @Test
      void update(){
          User user=new User();
          user.setId(6);
          user.setEmail("12345@qq.com");
  
          userMapper.updateById(user);
      }
      
       /**
       * 根据id删除用户
       */
      @Test
      void delete(){
          userMapper.deleteById(7);
      }
  
  }
  
  

  复杂的查询（删改同理）

  // 测试批量查询！
  @Test public void testSelectByBatchId(){
      //查询id为1、2、3的用户
      List<User> users = userMapper.selectBatchIds(Arrays.asList(1, 2, 3));
      users.forEach(System.out::println); 
  }
  
  // 按条件查询之使用map操作
  @Test public void testSelectByBatchIds(){
      HashMap<String, Object> map = new HashMap<>(); 
      // 自定义要查询，查询name为yl01且age为3的用户
      map.put("name","yl01");
      map.put("age",3); 
      List<User> users = userMapper.selectByMap(map); 
      users.forEach(System.out::println);
  }