Master Spring Boot & MyBatis: Complete Setup, Mapper Scanning, and Unit Testing Guide

Environment

Spring Boot 2.3.11 + MyBatis 3.5.6

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>2.1.4</version>
</dependency>
<dependency>
  <groupId>com.github.pagehelper</groupId>
  <artifactId>pagehelper-spring-boot-starter</artifactId>
  <version>1.3.0</version>
</dependency>

Application Configuration

pagehelper:
  helperDialect: mysql
  reasonable: true
  pageSizeZero: true
  offsetAsPageNum: true
  rowBoundsWithCount: true
---
mybatis:
  type-aliases-package: com.pack.domain
  configuration:
    lazy-loading-enabled: false
    aggressive-lazy-loading: false
    logImpl: org.apache.ibatis.logging.stdout.StdOutImpl
    mapUnderscoreToCamelCase: true

For detailed configuration, refer to the official documentation.

Pagination configuration:

MyBatis configuration:

Adding Mapper Scan to the Startup Class

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

After adding @MapperScan, individual @Mapper annotations on each mapper are unnecessary.

Core processing class: MapperScannerRegistrar.java

public class MapperScannerRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware {
    // implementation omitted
}

The ImportBeanDefinitionRegistrar interface is used to dynamically register beans, similar to how EnableFeignClients works.

Mapper Interface Definition

public interface UsersMapper {
    @Select("SELECT * FROM t_users")
    @Results(id = "users", value = {
        @Result(property = "name", column = "name", javaType = String.class),
        @Result(property = "password", column = "password")
    })
    List<Users> findAll();

    @Select("SELECT * FROM t_users WHERE id = #{id}")
    @ResultMap("users")
    Users findById(String id);

    @Insert("insert into t_users values(#{id}, #{password}, #{username})")
    int saveUsers(Users users);

    @Update("UPDATE t_users SET username = #{username}, password = #{password} WHERE id = #{id}")
    int updateUsers(Users users);

    @Delete("DELETE FROM t_users where id = #{id}")
    int deleteById(String id);

    @SelectProvider(type = UsersProvider.class, method = "selectLikeUsers")
    @ResultMap("users")
    List<Users> selectLikeUsers(Users users);

    @UpdateProvider(type = UsersProvider.class, method = "updateByProvider")
    int updateByProvider(@Param("users") Users users);
}

Note: Adding an id to @Results allows reuse via @ResultMap("users") in other methods. @*Provider annotations enable dynamic SQL definition.

Dynamic SQL Provider

public class UsersProvider {
    public String selectLikeUsers(Users users) {
        StringBuilder sql = new StringBuilder("SELECT * FROM t_users t where 1=1 ");
        if (users.getUsername() != null && users.getUsername().trim().length() > 0) {
            sql.append(String.format("and t.username like '%s'", "%" + users.getUsername() + "%"));
        }
        return sql.toString();
    }

    public String updateByProvider(@Param("users") Users users) {
        SQL sql = new SQL();
        sql.UPDATE("t_users")
           .SET("username = #{users.username}", "password = #{users.password}")
           .WHERE("id = #{users.id}");
        return sql.toString();
    }
}

Unit Tests

@RunWith(SpringRunner.class)
@SpringBootTest
public class UsersMapperTest {

    @Resource
    private UsersMapper usersMapper;

    @Test
    public void testFindAll() {
        Page<Users> page = PageHelper.startPage(1, 2);
        usersMapper.findAll();
        System.out.println(page.getResult());
        System.out.println(page.getTotal() + "
" + page.getPages());
    }

    @Test
    public void testFindById() {
        System.out.println(usersMapper.findById("1"));
    }

    @Test
    public void testSaveUsers() {
        Users users = new Users();
        users.setId("4");
        users.setPassword("123456");
        users.setUsername("zhangsan");
        System.out.println(usersMapper.saveUsers(users));
    }

    @Test
    public void testUpdateUser() {
        Users users = new Users();
        users.setId("3");
        users.setPassword("111111");
        users.setUsername("zhangsan");
        System.out.println(usersMapper.updateUsers(users));
    }

    @Test
    public void testDeleteById() {
        System.out.println(usersMapper.deleteById("3"));
    }

    @Test
    public void testSelectLikeUsers() {
        Users users = new Users();
        users.setUsername("gu");
        System.out.println(usersMapper.selectLikeUsers(users));
    }

    @Test
    public void testUpdateByProvider() {
        Users users = new Users();
        users.setId("2");
        users.setPassword("111111");
        users.setUsername("guest");
        System.out.println(usersMapper.updateByProvider(users));
    }
}

End of tutorial.