spring注解使用

• @Component/Service/Controller：管理bean
• @Scope：bean范围，可以指定单例，多例，session，request，也可以指定动态代理模式。

@Component
@Scope(value = DefaultListableBeanFactory.SCOPE_PROTOTYPE, proxyMode = ScopedProxyMode.TARGET_CLASS)
public class ScopeProxyBean {

    public void test(){
        System.out.println("aaaa");
    }
}

• @Conditional：定义类实现Conditional接口，bean被spring管理条件

public class MyCondition implements Condition {

    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        Environment env = context.getEnvironment();
        String system = env.getProperty("os.name");
        System.out.println("系统环境为 ==="+system);
        // 系统环境在Windows才加载该bean到容器中
        if(system.contains("Windows")){
            return false;
        }
        return true;
    }
}

@Component
@Conditional(MyCondition.class)
public class TestCondition {
}

• @AliasFor
• @PropertySources与PropertySource

@Configuration
@ComponentScan(basePackages = {"com.example.demo.bean"})
//@Conditional(MyCondition.class)
@PropertySource("classpath:application.properties")
public class MainConfig {

    @Bean(autowire = Autowire.BY_NAME)
    public AwareBean awareBean(){
        return new AwareBean();
    }

    @Component
    class TestMainConfig{

    }

}

@Component
//@Conditional(MyCondition.class)
public class TestCondition {

    @Value("${server.port}")
    private String port;

    public String getPort() {
        return port;
    }

    public void setPort(String port) {
        this.port = port;
    }
}

• @Import/ImportSelector/DeferredImportSelector与ImportAware
  ImportAware：获取注解上的值，作用参考EnableAsync注解

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(ProxyConfig.class)
public @interface ImportTest {
    String importTest() default "";
}

@Component
public class ProxyConfig implements ImportAware {

  AnnotationAttributes annotationAttributes;

  @Override
  public void setImportMetadata(AnnotationMetadata importMetadata) {
      annotationAttributes = AnnotationAttributes.fromMap(importMetadata.getAnnotationAttributes(ImportTest.class.getName()));
      System.out.println("=====" + annotationAttributes.getString("importTest"));
  }
}

Import与ImportSelector/DeferredImportSelector，可以导入bean，实现DeferredImportSelector有延迟效果。

public class ImportSelectorTest implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        System.out.println("ImportSelectorTest");
        return new String[]{"com.example.demo.bean.importAware.test1"};
    }
}
public class DeferredImportSelectorTest implements DeferredImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        System.out.println("DeferredImportSelectorTest");
        return new String[]{"com.example.demo.bean.importAware.test2"};
    }
}
// 启动类添加@Import({ImportSelectorTest.class, DeferredImportSelectorTest.class})

@DependsOn

@Component
@DependsOn({"dependB"})
public class DependA {

    @Autowired
    private DependB dependB;
}