spring-boot-route（八）整合mybatis操作數據庫

本文轉載自查看原文 2020-10-07 23:40 477 spring-boot-route

MyBatis 是一款優秀的持久層框架，它支持定制化 SQL、存儲過程以及高級映射。MyBatis 避免了幾乎所有的 JDBC 代碼和手動設置參數以及獲取結果集。MyBatis 可以使用簡單的 XML 或注解來配置和映射原生信息，將接口和 Java 的 POJOs(Plain Ordinary Java Object,普通的 Java對象)映射成數據庫中的記錄。

通過注解完成數據操作

第一步：引入mysql依賴和mybatis依賴

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>LATEST</version>
</dependency>

第二步：新建學生表及對應的實體類

CREATE TABLE `student` (
   `student_id` int(30) NOT NULL AUTO_INCREMENT,
   `age` int(1) DEFAULT NULL COMMENT '年齡',
   `name` varchar(45) DEFAULT NULL COMMENT '姓名',
   `sex` int(1) DEFAULT NULL COMMENT '性別：1：男，2：女，0：未知',
   `create_time` datetime DEFAULT NULL COMMENT '創建時間',
   `status` int(1) DEFAULT NULL COMMENT '狀態：1：正常，-1：刪除',
   PRIMARY KEY (`student_id`)
 ) ENGINE=InnoDB AUTO_INCREMENT=617354 DEFAULT CHARSET=utf8mb4 CHECKSUM=1 DELAY_KEY_WRITE=1 ROW_FORMAT=DYNAMIC COMMENT='學生表'

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student implements Serializable {

    private static final long serialVersionUID = 6712540741269055064L;

    private Integer studentId;
    private Integer age;
    private String name;
    private Integer sex;
    private Date createTime;
    private Integer status;
}

第三步：配置數據庫連接信息

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/simple_fast
    username: root
    password: root

增刪改查

@Mapper
public interface StudentMapper {

    @Select("select * from student where student_id = #{studentId}")
    Student findById(@Param("studentId") Integer studentId);

    @Insert("insert into student(age,name) values(#{age},#{name})")
    int addStudent(@Param("name") String name,@Param("age") Integer age);

    @Update("update student set name = #{name} where student_id = #{studentId}")
    int updateStudent(@Param("studentId") Integer studentId,@Param("name") String name);

    @Delete("delete from student where student_id = #{studentId}")
    int deleteStudent(@Param("studentId") Integer studentId);
}

上面演示的傳參方式是通過單個參數傳遞的，如果想通過Map或實體類傳參數，就不需要使用@Param來綁定參數了，將map中的key或者實體類中的屬性與sql中的參數值對應上就可以了。

通過XML配置完成數據操作

@Mapper和@MapperScan

@Mapper加在數據層接口上，將其注冊到ioc容器上，@MapperScan加在啟動類上，需要指定掃描的數據層接口包。如下：

@Mapper
public interface StudentMapper {}

@SpringBootApplication
@MapperScan("com.javatrip.mybatis.mapper")
public class MybatisApplication {
    public static void main(String[] args) {
        SpringApplication.run(MybatisApplication.class, args);
    }
}

兩個注解的作用一樣，在開發中為了方便，通常我們會使用@MapperScan。

指定mapper.xml的位置

mybatis:
  mapper-locations: classpath:mybatis/*.xml

開啟數據實體映射駝峰命名

mybatis:
  configuration:
    map-underscore-to-camel-case: true

編寫xml和與之對應的mapper接口

<?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.javatrip.mybatis.mapper.StudentXMapper">
    <select id="findById" resultType="com.javatrip.mybatis.entity.Student">
        select * from student where student_id = #{studentId}
    </select>
    <insert id="addStudent" parameterType="com.javatrip.mybatis.entity.Student">
        insert into student(name,age) values(#{name},#{age})
    </insert>
    
    <update id="updateStudent" parameterType="com.javatrip.mybatis.entity.Student">
        update student set name = #{name} where  student_id = #{studentId}
    </update>

    <delete id="deleteStudent" parameterType="Integer">
        delete from student where student_id = #{studentId}
    </delete>
</mapper>

@Mapper
public interface StudentXMapper {

    Student findById(@Param("studentId") Integer studentId);

    int addStudent(Student student);

    int updateStudent(@Param("studentId") Integer studentId,@Param("name") String name);

    int deleteStudent(@Param("studentId") Integer studentId);
}

編寫測試類

@SpringBootTest
class MybatisApplicationTests {

    @Autowired
    StudentMapper mapper;

    @Autowired
    StudentXMapper xMapper;

    @Test
    void testMapper() {

        Student student = mapper.findById(10);
        mapper.addStudent("Java旅途",19);
        mapper.deleteStudent(31);
        mapper.updateStudent(10,"Java旅途");
    }

    @Test
    void contextLoads() {
        
        Student student = xMapper.findById(10);
        Student studentDo = new Student();
        studentDo.setAge(18);
        studentDo.setName("Java旅途呀");
        xMapper.addStudent(studentDo);
        xMapper.deleteStudent(32);
        xMapper.updateStudent(31,"Java旅途");
    }
}

這里有幾個需要注意的點：mapper標簽中namespace屬性對應的是mapper接口；select標簽的id對應mapper接口中的方法名字；select標簽的resultType對應查詢的實體類，使用全路徑。