[Linux] 如何正确控制springboot中bean的加载顺序总结

1.为什么需要控制加载顺序​

{@code @Order} defines the sort order for an annotated component. Since Spring 4.0, annotation-based ordering is supported for many kinds of components in Spring, even for collection injection where the order values of the target components are taken into account (either from their target class or from their {@code @Bean} method). While such order values may influence priorities at injection points, please be aware that they do not influence singleton startup order which is an orthogonal concern determined by dependency relationships and {@code @DependsOn} declarations (influencing a runtime-determined dependency graph).

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• 控制AOP的类的加载顺序，也就是被​​@Aspect​​标注的类
  
• 控制​​ApplicationListener​​实现类的加载顺序
  
• 控制​​CommandLineRunner​​实现类的加载顺序
  
  
  
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@Configuration
public class BeanOrderConfiguration {

@Bean
@DependsOn("beanB")
public BeanA beanA(){
System.out.println("bean A init");
return new BeanA();
  }

@Bean
public BeanB beanB(){
System.out.println("bean B init");
return new BeanB();
  }

@Bean
@DependsOn({"beanD","beanE"})
public BeanC beanC(){
System.out.println("bean C init");
return new BeanC();
  }

@Bean
@DependsOn("beanE")
public BeanD beanD(){
System.out.println("bean D init");
return new BeanD();
  }

@Bean
public BeanE beanE(){
System.out.println("bean E init");
return new BeanE();
  }
}

bean B init
bean A init
bean E init
bean D init
bean C init

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• 直接或者间接标注在带有​​@Component​​注解的类上面;
  
• 直接或者间接标注在带有​​@Bean​​注解的方法上面;
  
• 使用​​@DependsOn​​注解到类层面仅仅在使用 component-scanning 方式时才有效，如果带有​​@DependsOn​​注解的类通过XML方式使用，该注解会被忽略，​​<bean depends-on="..."/>​​这种方式会生效。
  
  
  
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@Bean
public BeanA beanA(BeanB demoB){
  System.out.println("bean A init");
  return new BeanA();
}

@Bean
public BeanB beanB(){
  System.out.println("bean B init");
  return new BeanB();
}

@Configuration
@AutoConfigureOrder(2)
public class BeanOrderConfiguration1 {
@Bean
public BeanA beanA(){
System.out.println("bean A init");
return new BeanA();
  }
}

@Configuration
@AutoConfigureOrder(1)
public class BeanOrderConfiguration2 {
@Bean
public BeanB beanB(){
System.out.println("bean B init");
return new BeanB();
  }
}

@Configuration
@AutoConfigureOrder(10)
public class BeanOrderConfiguration1 {
@Bean
public BeanA beanA(){
System.out.println("bean A init");
return new BeanA();
  }
}

@Configuration
@AutoConfigureOrder(1)
public class BeanOrderConfiguration2 {
@Bean
public BeanB beanB(){
System.out.println("bean B init");
return new BeanB();
  }
}

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.example.demo.BeanOrderConfiguration1,\
  com.example.demo.BeanOrderConfiguration2