Spring静态Bean的原理
最近遇到一个spring static bean的坑，我们知道使用Java Config的方式定义一个Bean 非常简单，只需在Configuration的method上加上 @Bean 注解即可。 但是这里有个例外，假如你的Bean不是一个普通的Bean，而是一个BeanFactoryPostProcessor就需要使用static方法来定义这个Bean。 否则你会得到一个警告： @Bean method TestConfig.customEditorConfigurer is non-static and returns an object assignable to Spring's BeanFactoryPostProcessor interface. This will result in a failure to process annotations such as @Autowired, @Resource and @PostConstruct within the method's declaring @Configuration class. Add the 'static' modifier to this method to avoid these container lifecycle issues; see @Bean javadoc for complete details. 也就是说，如果你的bean是一个BFPP，必须定义为static，否则，使用@Autowired, @Resource and @PostConstruct 会有问题。 来看 @Bean注解源码里的注释： 1234567891011121314Special consideration must be taken for @Bean methods that return Spring BeanFactoryPostProcessor (BFPP) types. Because BFPP objects must be instantiated very early in the container lifecycle,they can interfere with processing of annotations such as @Autowired, @Value, and @PostConstruct within @Configuration classes. To avoid these lifecycle issues, mark BFPP-returning @Bean methods as static. For example: @Bean public static PropertySourcesPlaceholderConfigurer pspc() { // instantiate, configure and return pspc ... } By marking this method as static, it can be invoked without causing instantiation of its declaring @Configuration class, thus avoiding the above-mentioned lifecycle conflicts. Note however that static @Bean methods will not be enhanced for scoping and AOP semantics as mentioned above. This works out in BFPP cases, as they are not typically referenced by other @Bean methods. As a reminder, a WARN-level log message will be issued for any non-static @Bean methods having a return type assignable to BeanFactoryPostProcessor. 因为BFPP都需要在在Spring容器的早期进行实例化，因为他们会干扰正常的Bean实例化中处理 @Autowired @Value @PostConstruct ，这篇Blog尝试寻找一下Static Bean背后的原理。