mybatis的基于注解和xml的两种实现方式详解

文章简介

本文介绍了springboot+mybatis实现数据库操作的两种实现方式，经测试均可运行使用。整体而言注解更加简便，但面对一些复杂查询，可能需要使用到注解方式。

注解方式

pom依赖：

<dependencies>
        <!--连接数据库-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.1</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>
    </dependencies>

application.yaml配置文件

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mmall_learning?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver #com.mysql.cj.jdbc.Driver

Controller层

@RestController
public class UserController {
    @Autowired
    private UserService userService;
    
    @RequestMapping(value = "/get_user", method = RequestMethod.GET)
    public ResponseEntity<User> getUser(@RequestParam(value = "id") String userId) {
        User user = userService.getUser(userId);
        return ResponseEntity.status(HttpStatus.OK).body(user);
    }
}

Service层

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public User getUser(String userId) {
        User user = userMapper.findById(userId);
        return user;
    }

}

Dao层

@Mapper
public interface UserMapper {

    @Select("SELECT * FROM mmall_user WHERE ID = #{id}")
    User findById(@Param("id") String id);
}

实体类

@Data
public class User {
    private Integer id;
    private String username;
    private String password;
    private String email;
}

评析：注解方式非常简便，没有额外的配置工作。

xml方式

xml方式相对来说会需要配置一些路径参数，如果各位想通过这种方式实现数据库操作，可以参照以下目录结构和对应路径配置来实现。

目录结构

pom依赖：

	<dependencies>
        <!--连接数据库-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.1</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>

        <!-- Mybatis核心 仅xml方式需要加入该依赖，注解方式不需要 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
    </dependencies>

application.yaml配置文件：

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mmall_learning?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver #com.mysql.cj.jdbc.Driver

# 配置Mybatis文件位置，告诉Spring Boot你需要扫描的位置
mybatis:
  mapper-locations: classpath:com.example.demo.dao/*.xml

UserMapper.xml

<?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.example.demo.mmall.dao.UserMapper">
    <select id="findById" parameterType="int" resultType="com.example.demo.mmall.bean.User">
    SELECT * FROM mmall_user WHERE id = #{id}
  </select>
</mapper>

Controller层

@RestController
public class UserController {
    @Autowired
    private UserService userService;
    
    @RequestMapping(value = "/get_user", method = RequestMethod.GET)
    public ResponseEntity<User> getUser(@RequestParam(value = "id") String userId) {
        User user = userService.getUser(userId);
        return ResponseEntity.status(HttpStatus.OK).body(user);
    }
}

Service层

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public User getUser(String userId) {
        User user = userMapper.findById(Integer.valueOf(userId));
        return user;
    }

}

Dao层

@Mapper
public interface UserMapper {
    User findById(@Param("id") Integer id);
}

实体类

@Data
public class User {
    private Integer id;
    private String username;
    private String password;
    private String email;
}

评析：XML方式需要做些额外的配置工作，包括新建xml映射文件、在application.yaml中配置扫描路径等。但总体来说，比原来spring+mybatis使用xml方式实现数据库操作的配置已经简便不少了。

测试结果

以上两种方式测试结果均如下所示，可以正常查询到所需数据。

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