从Spring 2.5 开始,自动装配功能进行了多次改进,可以通过@Autowired或者@Resource注解一个设值方法,构造字段,属性甚至任意方法自动装配特定的属性。
为了要求Spring 自动装配具有@Autowired或者@Resource注解的属性,必须在IOC容器中注册一个AutowiredAnnotationBeanPostProcessor实例。在上下文中什么实例:
写道
<bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor"/>
也可以在bean的配置文件中包含<context:annotation-config/>元素。或者是
写道
<context:component-scan base-package="*"></context:component-scan>
默认情况下所有带@Autowired的属性都是必须的,如果没有找到匹配的Bean就会抛出如下异常
写道
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sequenceGenerator': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private SpringInAction.IOC.PrefixGenerator SpringInAction.IOC.SequenceGeneratorImpl.prefixGenerator; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [SpringInAction.IOC.PrefixGenerator] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:287)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1106)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:607)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:925)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:472)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
at SpringInAction.IOC.App.main(App.java:14)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private SpringInAction.IOC.PrefixGenerator SpringInAction.IOC.SequenceGeneratorImpl.prefixGenerator; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [SpringInAction.IOC.PrefixGenerator] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:513)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:92)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:284)
... 13 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [SpringInAction.IOC.PrefixGenerator] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:947)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:816)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:730)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:485)
... 15 more
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:287)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1106)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:607)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:925)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:472)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
at SpringInAction.IOC.App.main(App.java:14)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private SpringInAction.IOC.PrefixGenerator SpringInAction.IOC.SequenceGeneratorImpl.prefixGenerator; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [SpringInAction.IOC.PrefixGenerator] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:513)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:92)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:284)
... 13 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [SpringInAction.IOC.PrefixGenerator] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:947)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:816)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:730)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:485)
... 15 more
如果你希望某个属性是可选的可以将@Autowired的required属性设置为false 。这样当Spring 找不到匹配的bean之后,将不设置该属性。
写道
@Autowired(required=false)
private PrefixGenerator prefixGenerator;
private PrefixGenerator prefixGenerator;
运行结果:
ABC10000A
ABC10001A
默认情况下,按照类型自动装配在IOC容器中有超过一个类型兼容性的Bean时无效,但是Spring 允许指定一个候选Bean 这个Bean的名称在@Qulifier注解中提供。
相关推荐
通过@Bean 和spring的factoryBean注入的bean. 以及对应@service注解注入的类 通过@Autowired 注入对象的时间是现根据类型在根据beanName获取的案例集合
NULL 博文链接:https://forestqqqq.iteye.com/blog/2235292
Spring框架中 @Autowired 和 @Resource 注解的区别 在 spring 框架中,除了使用其特有的注解外,使用基于 JSR-250 的注解,它包括 @PostConstruct, @PreDestroy 和 @Resource 注释。 首先,咱们简单了解 @...
主要介绍了详解Spring依赖注入:@Autowired,@Resource和@Inject区别与实现原理,小编觉得挺不错的,现在分享给大家,也给大家做个参考。一起跟随小编过来看看吧
Spring注解@Resource和@Autowired.doc
Spring@Autowired注解与自动装配.rar
本篇文章主要介绍最重要的三个Spring注解,也就是@Autowired、@Resource和@Service,具有很好的参考价值。下面跟着小编一起来看下吧
自定义标签中@Autowired的属性为null 解决办法:两步 1.新建一个类SpringContext,实现接口ApplicationContextAware; 2.spring.xml中添加<bean id="" class="com............SpringContext"> 3.使用SpingContext....
主要介绍了Spring使用@Autowired为抽象父类注入依赖代码实例,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
主要介绍了详解SpringBoot 多线程处理任务 无法@Autowired注入bean问题解决,小编觉得挺不错的,现在分享给大家,也给大家做个参考。一起跟随小编过来看看吧
@Autowired使用 构造函数注入 public Class Outer { private Inner inner; @Autowired public Outer(Inner inner) { this.inner = inner; } } 属性注入 public Class Outer { @Autowired private Inner ...
SSH笔记-通过@Autowired配置注入关系的demo,续上一篇文章中的annotation笔记
主要介绍了Spring注解@Resource和@Autowired区别对比详解,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
主要介绍了Spring Boot 自定义 Shiro 过滤器无法使用 @Autowired问题及解决方法 ,本文给大家介绍的非常详细,具有一定的参考借鉴价值,需要的朋友可以参考下
【Java面试】@Resource 和 @Autowired 的区别.doc
主要介绍了SpringBoot项目使用多线程处理任务时无法通过@Autowired注入bean问题的解决方法,需要的朋友可以参考下
@Resource和@Autowired都是做bean的注入时使用,其实@Resource并不是Spring的注解,它的包是javax.annotation.Resource,需要导入,但是Spring支持该注解的注入。 1、共同点 两者都可以写在字段和setter方法上。两者...