@Value注解不能注入static修饰的属性

1：问题描述

配置文件application.yml：

person.name: nobody
person.age: 20

  

 

  
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实体类Person：

package com.nobody.pojo.entity;

import java.io.Serializable;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class Person implements Serializable { /** * */ private static final long serialVersionUID = -8245392957106320519L; @Value("${person.name}") private static String name; private static String age; @Value("${person.age}") public void setAge(String age) { Person.age = age; } public void setName(String name) { Person.name = name; } public static String getName() { return name; } public static String getAge() { return age; }

}

  

 

  
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测试接口类DemoController：

package com.nobody.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.nobody.ehr.pojo.entity.Person;

@RequestMapping("demo")
@RestController
public class DemoController { @GetMapping public String demo() { System.out.println("name:" + Person.getName() + ", age:" + Person.getAge()); return ""; }

}

  

 

  
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测试结果：
@Value注解放在属性上注入值失败，而@Value放在setter方法上(注意，该方法也不能是静态方法)注入成功。

name:null, age:20

  

 

  
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2：分析

启动日志：

[19:37:45] INFO  [restartedMain] o.s.b.f.a.AutowiredAnnotationBeanPostProcessor - Autowired annotation is not supported on static fields: private static java.lang.String com.nobody.pojo.entity.Person.name

  

 

  
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源码分析：

private InjectionMetadata buildAutowiringMetadata(final Class<?> clazz) {
		List<InjectionMetadata.InjectedElement> elements = new ArrayList<>();
		Class<?> targetClass = clazz; do { final List<InjectionMetadata.InjectedElement> currElements = new ArrayList<>(); ReflectionUtils.doWithLocalFields(targetClass, field -> { AnnotationAttributes ann = findAutowiredAnnotation(field); if (ann != null) { //这里对静态属性注入做了过滤 if (Modifier.isStatic(field.getModifiers())) { if (logger.isInfoEnabled()) { logger.info("Autowired annotation is not supported on static fields: " + field); } return; } boolean required = determineRequiredStatus(ann); currElements.add(new AutowiredFieldElement(field, required)); } }); ReflectionUtils.doWithLocalMethods(targetClass, method -> { Method bridgedMethod = BridgeMethodResolver.findBridgedMethod(method); if (!BridgeMethodResolver.isVisibilityBridgeMethodPair(method, bridgedMethod)) { return; } AnnotationAttributes ann = findAutowiredAnnotation(bridgedMethod); if (ann != null && method.equals(ClassUtils.getMostSpecificMethod(method, clazz))) { //这里对静态方法做了过滤 if (Modifier.isStatic(method.getModifiers())) { if (logger.isInfoEnabled()) { logger.info("Autowired annotation is not supported on static methods: " + method); } return; } if (method.getParameterCount() == 0) { if (logger.isInfoEnabled()) { logger.info("Autowired annotation should only be used on methods with parameters: " + method); } } boolean required = determineRequiredStatus(ann); PropertyDescriptor pd = BeanUtils.findPropertyForMethod(bridgedMethod, clazz); currElements.add(new AutowiredMethodElement(method, required, pd)); } }); elements.addAll(0, currElements); targetClass = targetClass.getSuperclass();
		}
		while (targetClass != null && targetClass != Object.class); return new InjectionMetadata(clazz, elements);
	}

  

 

  
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3：结论

从源码上发现，理论上spring是可以对静态域注入的，只是spring没有这样做，它认为依赖注入发生的时段是在实例的生命周期，而不是类的生命周期。

文章来源: javalib.blog.csdn.net，作者：陈皮的JavaLib，版权归原作者所有，如需转载，请联系作者。

原文链接：javalib.blog.csdn.net/article/details/105229998