Understanding Spring Boot Starters with MyBatis: mybatis‑spring vs mybatis‑spring‑boot‑starter

The article uses MyBatis as an example to illustrate what a Spring Boot Starter is, why it exists, and how it works. It first defines a Starter as a Maven module that packages a component's dependencies and auto‑configuration, enabling developers to add functionality with a single dependency.

It then compares the traditional mybatis-spring integration with the mybatis-spring-boot-starter approach, showing that the starter reduces boilerplate configuration such as creating mybatis-config.xml, defining DataSource, SqlSessionFactoryBean, and MapperScannerConfigurer beans.

Spring (non‑Boot) integration steps include:

Adding Spring, MyBatis, and JDBC dependencies.

Creating mybatis-config.xml with property placeholders, settings, mapper packages, and bean definitions for data source, session factory, and mapper scanner.

Writing mapper XML files and Java interfaces.

Calling mapper methods in business code.

For Spring Boot, the process is simplified to:

Adding the mybatis-spring-boot-starter dependency.

Configuring the datasource and mapper locations in application.properties.

spring.datasource.username=xxxx
spring.datasource.password=xxxx
spring.datasource.url=jdbc:mysql://...
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
mybatis.mapper-locations=classpath:mapper/*.xml

Creating mapper interfaces annotated with @Mapper and corresponding XML files.

Injecting the mapper with @Autowired and invoking methods.

The starter automatically handles:

Dependency management, avoiding version conflicts.

Discovery and registration of an existing DataSource.

Creation and registration of SqlSessionFactory and SqlSessionTemplate beans.

Scanning of @Mapper interfaces and registering them as beans.

Internally, the starter’s mybatis-spring-boot-autoconfigure module uses Spring’s SPI mechanism to load MybatisAutoConfiguration, which performs the above tasks, including an AutoConfiguredMapperScannerRegistrar that registers mapper bean definitions.

Overall, using the starter dramatically reduces configuration code and improves developer productivity when integrating MyBatis with Spring Boot.