Using MyBatis3 Annotations to Replace XML Configuration: A Comprehensive Guide

The article introduces MyBatis3 annotation support as a way to gradually replace XML configuration, showing how @Select and @SelectProvider can be used to write SQL directly in Java code and handle dynamic queries for complex business needs.

Basic CRUD annotations – MyBatis provides @Select, @Insert, @Update, and @Delete for the majority of data‑access operations. An example interface demonstrates a simple @Select query without any XML:

@Mapper
public interface UserMapper {
    @Select("select * from t_user")
    List<User> list();
}

Result mapping annotations – When column names do not follow the default underscore‑to‑camel‑case conversion, @Results and @Result can explicitly map database fields to object properties. The article shows a @Results example that maps USER_ID, USERNAME, PASSWORD, and PHONE_NUM to the corresponding fields in the User class.

@Results({
    @Result(property = "userId", column = "USER_ID"),
    @Result(property = "username", column = "USERNAME"),
    @Result(property = "password", column = "PASSWORD"),
    @Result(property = "mobileNum", column = "PHONE_NUM")
})
@Select("select * from t_user")
List<User> list();

Advanced provider annotations – @SelectProvider, @InsertProvider, @UpdateProvider, and @DeleteProvider enable dynamic SQL generation via a separate Java class. The guide includes a @SelectProvider example that calls UserSqlProvider.listByUsername.

@SelectProvider(type = UserSqlProvider.class, method = "listByUsername")
List<User> listByUsername(String username);

public class UserSqlProvider {
    public String listByUsername(String username) {
        return "select * from t_user where username = #{username}";
    }
}

Step‑by‑step tutorial

1. Dependencies – Maven coordinates for Spring Boot Web, MyBatis Spring Boot Starter, MySQL driver, and test libraries are added.

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <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>
        <scope>runtime</scope>
    </dependency>
</dependencies>

2. Application configuration – The application.yml file enables the MyBatis underscore‑to‑camel‑case mapping and configures the datasource and SQL logging.

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/socks?useSSL=false
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
mybatis:
  configuration:
    map-underscore-to-camel-case: true
logging:
  level:
    com.hehe.mapper: debug

3. Data‑layer code – The UserMapper interface contains CRUD methods, @SelectProvider for dynamic SQL, and @Results for explicit column mapping.

package com.hehe.mapper;
@Mapper
public interface UserMapper {
    @Select("select * from t_user")
    List<User> list();

    @SelectProvider(type = UserSqlProvider.class, method = "listByUsername")
    List<User> listByUsername(String username);

    @Results({
        @Result(property = "userId", column = "USER_ID"),
        @Result(property = "username", column = "USERNAME"),
        @Result(property = "password", column = "PASSWORD"),
        @Result(property = "mobileNum", column = "PHONE_NUM")
    })
    @Select("select * from t_user")
    List<User> listSample();
}

4. SQL provider – The UserSqlProvider class shows two ways to build SQL: a simple string return and a dynamic builder using MyBatis' SQL API.

public class UserSqlProvider {
    public String listByUsername(String username) {
        return "select * from t_user where username = #{username}";
    }

    public String getBadUser(@Param("username") String username, @Param("password") String password) {
        return new SQL() {{
            SELECT("*");
            FROM("t_user");
            if (username != null && password != null) {
                WHERE("username like #{username} and password like #{password}");
            } else {
                WHERE("1=2");
            }
        }}.toString();
    }
}

5. Entity class – A plain Java User POJO with fields matching the database columns.

public class User {
    private String userId;
    private String username;
    private String password;
    private String mobileNum;
    // getters & setters
}

6. Database script – SQL statements to create the t_user table and insert two sample rows.

USE `SOCKS`;
DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user` (
  `USER_ID` varchar(50),
  `USERNAME` varchar(50),
  `PASSWORD` varchar(50),
  `PHONE_NUM` varchar(15)
);
INSERT INTO `t_user` VALUES ('1','admin','admin','15011791234');
INSERT INTO `t_user` VALUES ('2','roots','roots','18812342017');

7. Controller layer – A Spring Boot @RestController exposing endpoints to list users, query by username, and perform login‑style lookups.

package com.hehe.controller;
@RestController
@RequestMapping("/user/*")
public class UserController {
    @Autowired
    UserMapper userMapper;

    @GetMapping("list")
    public List<User> list() { return userMapper.list(); }

    @GetMapping("list/{username}")
    public List<User> listByUsername(@PathVariable("username") String username) {
        return userMapper.listByUsername(username);
    }

    @GetMapping("get/{username}/{password}")
    public User get(@PathVariable("username") String username,
                    @PathVariable("password") String password) {
        return userMapper.get(username, password);
    }
}

8. Running and testing – After starting the Spring Boot application, the endpoints http://localhost:8080/user/list and http://localhost:8080/user/list/admin return the full user list and the record for the user admin, respectively.

9. Source code and documentation – The complete project is hosted at https://github.com/yizhiwazi/springboot-socks , and the official MyBatis Java API documentation can be found at http://www.mybatis.org/mybatis-3/zh/java-api.html .