mybatis通過if語句增刪改查

有時候爲了簡化我們的代碼。

1 舉個例子

Student類：

@Data
public class Student {
    private Integer id;
    private Integer age;
    private Integer sno;
}

有時候我們想通過age這個屬性獲取Student對象
有時候我們也想通過sno這個屬性獲取Student對象

難道我們在DAO層寫兩個接口？
比如這樣子？

Student getStudentByAge(Int age);
Student getStudentBySno(Int sno);

那麼在mapper文件中要這樣寫？

    <select id="getStudentByAge" parameterType="int" resultMap="studentMap">
        select * from student where age=#{age}
    </select>
    <select id="getStudentBySno" parameterType="int" resultMap="studentMap">
        select * from student where sno=#{sno}
    </select>

顯然，這樣子是不高效的

2 上手測試 實驗

實體類 Student：

@Data
public class Student {
    @ApiModelProperty(name = "id",example = "1",position = 1)
    private Integer id;
    @ApiModelProperty(name = "age",value = "年齡",example = "18",position = 2)
    private Integer age;
    @ApiModelProperty(name = "sno",value = "學號",example = "334",position = 3)
    private Integer sno;
}

數據庫：

CREATE TABLE `student` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `age` int(11) DEFAULT NULL COMMENT '年齡',
  `sno` int(11) NOT NULL COMMENT '學號',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

手動添加一些數據

Dao層：

@Mapper
public interface StudentDao {

    /**
     * @description: 通過student中的屬性 查詢到student
     * @param: student
     * @author: Yuz
     * @creat_time: 2019/8/20
     * @return: student
    **/
    Student getStudent(Student student);

    /**
     * @description: 通過age sno 屬性來刪除
     * @param: student
     * @author: Yuz
     * @creat_time: 2019/8/20
     * @return: void
    **/
    void deleteStudent(Student student);

}

Mapper

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.dao.StudentDao">
    <resultMap id="studentMap" type="com.entity.Student">
        <id property="id" column="id"/>
        <result property="age" column="age"/>
        <result property="sno" column="sno"/>
    </resultMap>

    <select id="getStudent" parameterType="com.entity.Student" resultMap="studentMap">
        select * from student where
        <if test="age != null">age=#{age}</if>
        <if test="sno !=null">sno=#{sno}</if>
    </select>

    <delete id="deleteStudent" parameterType="Student">
        delete from student
        <where>
            <if test="age != null">
                age =#{age}
            </if>
            <if test="sno != sno">
                sno=#{sno}
            </if>
        </where>
    </delete>

</mapper>

Service層：

@Service
public class StudentService {

    @Autowired
    StudentDao studentDao;


    /**
     * @description: 通過student中的屬性 查詢到student
     * @param: student
     * @author: Yuz
     * @creat_time: 2019/8/20
     * @return: student
     **/
    public Student getStudent(Student student){
        return studentDao.getStudent(student);
    }

    /**
     * @description: 通過age sno 屬性來刪除
     * @param: student
     * @author: Yuz
     * @creat_time: 2019/8/20
     * @return: void
     **/
    public void deleteStudent(Student student){
        studentDao.deleteStudent(student);
    }
}

Controller:

@RestController
@Api("學生接口")
@RequestMapping("/student")
public class StudentController {
    @Autowired
    StudentService studentService;


    /**
     * @description: 通過student中的屬性 查詢到student
     * @param: student
     * @author: Yuz
     * @creat_time: 2019/8/20
     * @return: student
     **/
    @ApiOperation("通過屬性查詢student")
    @PostMapping("/getStudent")
    Student getStudent(@RequestBody Student student){
        return studentService.getStudent(student);
    }

    /**
     * @description: 通過age sno 屬性來刪除
     * @param: student
     * @author: Yuz
     * @creat_time: 2019/8/20
     * @return: void
     **/
    @ApiOperation("通過屬性刪除student")
    @PostMapping("/delete")
    public void deleteStudent(@RequestBody Student student){
        studentService.deleteStudent(student);
    }
}

3 直接測試

通過age屬性查詢student：成功

通過sno屬性查詢:

通過屬性age刪除Student:

通過sno屬性刪除Student