Spring Annotation Development: From Bean Definition to MyBatis Integration

Spring 3.0 introduced pure annotation development to simplify configuration, especially when integrating with MyBatis.

1. Annotation Development

Annotations are special interfaces extending Annotation; at runtime they are implemented by dynamic proxy classes. When retrieving an annotation via reflection, a proxy object ($Proxy1) is returned, whose invoke method in AnnotationInvocationHandler reads values from the memberValues map sourced from the constant pool.

2. Defining Beans with Annotations

Previously beans were defined in XML:

<bean id="a" class="yu7daily.Dao.Daoimpl.A"/>

With annotations, the @Component("a") annotation on the class replaces the XML definition.

Scanning packages is done with <context:component-scan base-package="yu7daily.Dao"/> or the equivalent @ComponentScan("yu7daily.Dao") in a configuration class.

3. Bean Scope

Beans are singleton by default; use @Scope("prototype") to create non‑singleton beans.

4. Derived Annotations

Spring provides @Controller, @Service, and @Repository as specializations of @Component to distinguish presentation, business, and data layers.

5. Pure Annotation Mode

Configuration classes are marked with @Configuration and package scanning with @ComponentScan. The XML <context:component-scan/> can be fully replaced.

6. Dependency Injection

Field injection is achieved with @Autowired. When multiple beans of the same type exist, @Qualifier("beanName") together with @Autowired specifies the target bean, avoiding NoUniqueBeanDefinitionException.

7. Simple Value Injection

Use @Value("hello java") or @Value("${property}") to inject literal strings or properties from a file.

8. Reading Properties Files

Annotate a configuration class with @PropertySource("test.properties") and inject values with @Value("${name}").

9. Spring‑MyBatis Integration

Add spring-jdbc and mybatis-spring dependencies, configure a data source, create a main configuration class that imports JdbcConfig and MybatisConfig, and obtain beans via AnnotationConfigApplicationContext. This eliminates most XML configuration.

The article demonstrates that pure annotation development dramatically reduces boilerplate and simplifies Spring‑MyBatis projects.