手记

spring-boot-route(八)整合mybatis操作数据库

MyBatis 是一款优秀的持久层框架,它支持定制化 SQL、存储过程以及高级映射。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以使用简单的 XML 或注解来配置和映射原生信息,将接口和 Java 的 POJOs(Plain Ordinary Java Object,普通的 Java对象)映射成数据库中的记录。

通过注解完成数据操作

第一步:引入mysql依赖和mybatis依赖

mysqlmysql-connector-javaorg.mybatis.spring.bootmybatis-spring-boot-starterLATEST

第二步:新建学生表及对应的实体类

CREATE TABLE `student` (
   `student_id` int(30) NOT NULL AUTO_INCREMENT,
   `age` int(1) DEFAULT NULL COMMENT '年龄',
   `name` varchar(45) DEFAULT NULL COMMENT '姓名',
   `sex` int(1) DEFAULT NULL COMMENT '性别:1:男,2:女,0:未知',
   `create_time` datetime DEFAULT NULL COMMENT '创建时间',
   `status` int(1) DEFAULT NULL COMMENT '状态:1:正常,-1:删除',
   PRIMARY KEY (`student_id`)
 ) ENGINE=InnoDB AUTO_INCREMENT=617354 DEFAULT CHARSET=utf8mb4 CHECKSUM=1 DELAY_KEY_WRITE=1 ROW_FORMAT=DYNAMIC COMMENT='学生表'
@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:配置数据库连接信息

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

增删改查

@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);
}

上面演示的传参方式是通过单个参数传递的,如果想通过Map或实体类传参数,就不需要使用@Param来绑定参数了,将map中的key或者实体类中的属性与sql中的参数值对应上就可以了

通过XML配置完成数据操作

@Mapper和@MapperScan

@Mapper加在数据层接口上,将其注册到ioc容器上,@MapperScan加在启动类上,需要指定扫描的数据层接口包。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);
    }
}

两个注解的作用一样,在开发中为了方便,通常我们会使用@MapperScan。

指定mapper.xml的位置

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

开启数据实体映射驼峰命名

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

编写xml和与之对应的mapper接口

<?xml version="1.0" encoding="UTF-8" ?>


        select * from student where student_id = #{studentId}
    
        insert into student(name,age) values(#{name},#{age})
    
        update student set name = #{name} where  student_id = #{studentId}
    
        delete from student where student_id = #{studentId}
    
@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);
}

编写测试类

@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");
    }
}

这里有几个需要注意的点:mapper标签中namespace属性对应的是mapper接口;select标签的id对应mapper接口中的方法名字;select标签的resultType对应查询的实体类,使用全路径。

此是spring-boot-route系列的第八篇文章,这个系列的文章都比较简单,主要目的就是为了帮助初次接触Spring Boot 的同学有一个系统的认识。本文已收录至我的github,欢迎各位小伙伴star

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