springboot 注解说明（@EnableConfigurationProperties）

我会带着你远行 2023-02-23 03:54 89阅读 0赞

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### springboot 注解说明（@EnableConfgurationProperties） ###

**应用：带有@ConfigurationProperties注解的类A从配置文件中读取配置信息，@EnableConfigurationProperties将类A注册为容器的bean；**

**说明：可以不使用@EnableConfigurationProperties，直接在类A上加注解（@Component等）将其注册为容器的bean**

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**相关类与注解**

**@EnableConfigurationProperties：导入EnableConfigurationPropertiesRegistrar类**

@Target({ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Import({EnableConfigurationPropertiesRegistrar.class})
    public @interface EnableConfigurationProperties {
        String VALIDATOR_BEAN_NAME = "configurationPropertiesValidator";
    
        Class<?>[] value() default {};
    }

**EnableConfigurationPropertiesRegistrar**

class EnableConfigurationPropertiesRegistrar implements ImportBeanDefinitionRegistrar {
        EnableConfigurationPropertiesRegistrar() {
        }
    
        public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
            registerInfrastructureBeans(registry);
            ConfigurationPropertiesBeanRegistrar beanRegistrar = new ConfigurationPropertiesBeanRegistrar(registry);
                                                                //使用ConfigurationPropertiesBeanRegistrar将类注册为容器的bean
            this.getTypes(metadata).forEach(beanRegistrar::register);  //遍历value指定的类，进行注册                                           
        }
    
        private Set<Class<?>> getTypes(AnnotationMetadata metadata) {  //获取value指定的类                                      
            return (Set)metadata.getAnnotations().stream(EnableConfigurationProperties.class).flatMap((annotation) -> {
                return Arrays.stream(annotation.getClassArray("value"));
            }).filter((type) -> {
                return Void.TYPE != type;
            }).collect(Collectors.toSet());
        }
    
        static void registerInfrastructureBeans(BeanDefinitionRegistry registry) {
            ConfigurationPropertiesBindingPostProcessor.register(registry);
            BoundConfigurationProperties.register(registry);
            ConfigurationPropertiesBeanDefinitionValidator.register(registry);
            ConfigurationBeanFactoryMetadata.register(registry);
        }
    }

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**示例**

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**配置文件**

**application.yml**

person:
      name: 瓜田李下
      age: 20

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**pojo 层**

@Data
    @ConfigurationProperties(prefix = "person")
    public class Person {
    
        private String name;
        private Integer age;
    }

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**config 层**

**WebConfig：使用@EnableConfigurationProperties注解，将person注册为bean**

@Configuration
    @EnableConfigurationProperties(Person.class)
    public class WebConfig {
    }

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**controller 层**

**HelloController**

@RestController
    public class HelloController {
    
        @Resource
        private Person person;
    
        @RequestMapping("/hello")
        public String hello(){
            System.out.println(person);
    
            return "success";
        }
    }

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**使用测试**

**localhost:8080/hello**

2020-07-05 16:33:22.845  INFO 14192 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
    2020-07-05 16:33:22.852  INFO 14192 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 6 ms
    Person(name=瓜田李下, age=20)