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使用mybatis实现数据的基础增删改查,简单的增删改查操作方法步骤

代码实现

• pom.xml

<dependencies><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>3.0.4</version></dependency><dependency><groupId>com.mysql</groupId><artifactId>mysql-connector-j</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter-test</artifactId><version>3.0.4</version><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency></dependencies>

• EmpMapper.interface

/*** @author gaofeng* @date 2025-01-04 - 18:02*/
@Mapper
public interface EmpMapper {@Select("select * from tb_emp")public List<Emp> getAllEmpList();@Delete("delete from tb_emp where id = #{id}")public int deleteEmp(Integer id);
}

• pojo.java

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;import java.time.LocalDate;
import java.time.LocalDateTime;/*** @author gaofeng* @date 2025-01-04 - 17:58*/@Data
@AllArgsConstructor
@NoArgsConstructor
public class Emp {private Integer id;private String username;private String password;private String name;private Short gender;private String image;private Short job;private LocalDate entrydate;private Integer geptId;private LocalDateTime createTime;private LocalDateTime updateTime;
}

• application.properties文件

server.port=9090
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/javaweb
spring.datasource.username=root
spring.datasource.password=123456# 控制台输出mybatis的日志信息
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

• 测试效果

  • 查询所有数据

  @Testpublic void getAllEmpList(){List<Emp> allEmpList = empMapper.getAllEmpList();allEmpList.stream().forEach(emp -> {System.out.println(emp);});}
  

  

  • 根据id删除记录

  @Test
  public void deleteEmpById(){int count = empMapper.deleteEmp(17);System.out.println(count);
  }
  

  

  • 增加

    @Test
    public void insertEmp(){Emp emp = new Emp();emp.setUsername("Tom");emp.setName("汤姆");emp.setImage("1.jpg");emp.setGender((short)1);emp.setJob((short)1);emp.setEntrydate(LocalDate.of(2000,01,01));emp.setCreateTime(LocalDateTime.now());emp.setUpdateTime(LocalDateTime.now());emp.setDeptId(1);empMapper.insert(emp);
    }
    

    

  • 新增返回主键

    	@Options(keyProperty = "id",useGeneratedKeys = true)  // 加上这个注解@Insert("insert into tb_emp(username, name, gender, image, job, entrydate, dept_id, create_time, update_time) VALUES\n" +"            (#{username},#{name},#{gender},#{image},#{job},#{entrydate},#{deptId},#{createTime},#{updateTime})")public void insert(Emp emp);
    

    @Test
    public void insertEmp(){Emp emp = new Emp();emp.setUsername("Tom2");emp.setName("汤姆2");emp.setImage("1.jpg");emp.setGender((short)1);emp.setJob((short)1);emp.setEntrydate(LocalDate.of(2000,01,01));emp.setCreateTime(LocalDateTime.now());emp.setUpdateTime(LocalDateTime.now());emp.setDeptId(1);empMapper.insert(emp);System.out.println(emp.getId());
    }
    

    这样在数据库中就对应上了

    

  • 更新

        @Update("update tb_emp set username = #{username},name = #{name},gender = #{gender},\n" +"                  image=#{image},job=#{job},entrydate=#{entrydate},dept_id=#{deptId},\n" +"                  update_time=#{updateTime} where id = #{id}")public void update(Emp emp);
    

     @Testpublic void updateEmp(){Emp emp = new Emp();emp.setId(18);emp.setUsername("Tom3");emp.setName("汤姆3");emp.setImage("1.jpg");emp.setGender((short)1);emp.setJob((short)1);emp.setEntrydate(LocalDate.of(2000,01,01));emp.setUpdateTime(LocalDateTime.now());emp.setDeptId(1);empMapper.update(emp);
    //        System.out.println(emp.getId());}
    

    
    

  • 根据id查询

    @Select("select * from tb_emp where id = #{id}")public Emp getById(Integer id);
  

  // 根据id@Testpublic  void getById(){Emp emp = empMapper.getById(19);System.out.println(emp);}
  

解决方法一：就是起别名，需要列出所有的字段，不能用*代替了
解决方法二：使用Results注解

 	@Results({@Result(column = "dept_id",property = "deptId"),@Result(column = "create_time",property = "createTime"),@Result(column = "update_time",property = "updateTime")})@Select("select * from tb_emp where id = #{id}")public Emp getById(Integer id);	

解决方法三：使用mybatis的配置，开启识别驼峰命名

mybatis.configuration.map-underscore-to-camel-case = true

• 条件查询
  • 方式1

 @Select("select * from tb_emp where name like '%${name}%' and gender = #{gender}\n" +"and entrydate between #{begin} and #{end} order by update_time desc;\n")public List<Emp> listEmp(String name,Short gender, LocalDate begin,LocalDate end);

• 方式2

 @Select("select * from tb_emp where name like concat('%',#{name},'%') and gender = #{gender}\n" +"and entrydate between #{begin} and #{end} order by update_time desc;\n")public List<Emp> listEmp(String name,Short gender, LocalDate begin,LocalDate end);

@Testpublic void testList(){List<Emp> empList = empMapper.listEmp("张",(short)1, LocalDate.of(2010, 1, 1), LocalDate.of(2020, 1, 1));System.out.println(empList);}