{"id":1936,"date":"2025-02-17T17:27:21","date_gmt":"2025-02-17T09:27:21","guid":{"rendered":"https:\/\/www.fanyamin.com\/wordpress\/?p=1936"},"modified":"2025-02-17T17:27:52","modified_gmt":"2025-02-17T09:27:52","slug":"how-spring-boot-injects-sqlsessiontemplate-for-mapper-interfaces","status":"publish","type":"post","link":"https:\/\/www.fanyamin.com\/wordpress\/?p=1936","title":{"rendered":"How Spring Boot Injects `SqlSessionTemplate` for `@Mapper` Interfaces"},"content":{"rendered":"

In Spring Boot with MyBatis<\/strong>, the @Mapper<\/code> annotation is used to mark an interface as a MyBatis Mapper. Spring Boot automatically injects SqlSessionTemplate<\/code> behind the scenes<\/strong> to enable SQL execution for these mapper interfaces.<\/p>\n

How Spring Boot Injects SqlSessionTemplate<\/code> for @Mapper<\/code> Interfaces<\/strong><\/h3>\n

Spring Boot and MyBatis integrate through MyBatis-Spring-Boot-Starter<\/code>, which:<\/p>\n

    \n
  1. Scans for @Mapper<\/code> interfaces<\/strong> and registers them as Spring beans.<\/li>\n
  2. Automatically configures a SqlSessionFactory<\/code> and SqlSessionTemplate<\/code>.<\/strong><\/li>\n
  3. Injects SqlSessionTemplate<\/code> behind the scenes<\/strong> into each @Mapper<\/code> interface.<\/li>\n<\/ol>\n
    \n

    Example Setup<\/strong><\/h3>\n

    1. Add Dependencies<\/strong><\/h4>\n

    If using Maven, add:<\/p>\n

    <dependency>\n    <groupId>org.mybatis.spring.boot<\/groupId>\n    <artifactId>mybatis-spring-boot-starter<\/artifactId>\n    <version>3.0.3<\/version>\n<\/dependency><\/code><\/pre>\n
    2. Define the MyBatis @Mapper<\/code> Interface<\/strong><\/h4>\n
    @Mapper\npublic interface UserMapper {\n    @Select("SELECT * FROM users WHERE id = #{id}")\n    User findById(@Param("id") Long id);\n}<\/code><\/pre>\n
    3. Configure MyBatis in application.properties<\/code><\/strong><\/h4>\n
    spring.datasource.url=jdbc:mysql:\/\/localhost:3306\/mydb\nspring.datasource.username=root\nspring.datasource.password=root\nspring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver\nmybatis.mapper-locations=classpath:mappers\/*.xml<\/code><\/pre>\n
    4. Enable @MapperScan<\/code> in the @SpringBootApplication<\/code><\/strong><\/h4>\n
    @SpringBootApplication\n@MapperScan("com.example.mappers")  \/\/ Automatically scans @Mapper interfaces\npublic class MyApplication {\n    public static void main(String[] args) {\n        SpringApplication.run(MyApplication.class, args);\n    }\n}<\/code><\/pre>\n
    5. Use the UserMapper<\/code> in a Service<\/strong><\/h4>\n
    @Service\npublic class UserService {\n\n    @Autowired\n    private UserMapper userMapper;\n\n    public User getUserById(Long id) {\n        return userMapper.findById(id);\n    }\n}<\/code><\/pre>\n
    \n
    How SqlSessionTemplate<\/code> Works Behind the Scenes<\/strong><\/h3>\n