Spring5源码分析BeanFactoryPostProcessor

  • Z时代
  • 2024-01-10
  • 分类：综合

编程

上一篇：Spring5源码分析-BeanDefinitionRegistryPostProcessor

BeanFactoryPostProcessor可以完成对BeanDefinition的修改

源码：

public interface BeanFactoryPostProcessor {
	/**
	 * Modify the application context"s internal bean factory after its standard
	 * initialization. All bean definitions will have been loaded, but no beans
	 * will have been instantiated yet. This allows for overriding or adding
	 * properties even to eager-initializing beans.
	 * @param beanFactory the bean factory used by the application context
	 * @throws org.springframework.beans.BeansException in case of errors
	 * 在Spring的标准初始化完成之后，此时所有的符合Spring规则的BeanDefinition已经全部完成加载，但是还没有任何一个Bean被初始化，
	 * Spring允许咋们可以覆盖或者添加新的属性
	 *
	 */
	void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
}

 

测试用例代码如下：

@Component
@Getter
@Setter
public class ProcessorUser implements BeanFactoryAware {
	private BeanFactory beanFactory;
	@Value("${name}")
	private String name;
	@Value("${age}")
	private Integer age;
	@Override
	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		this.beanFactory = beanFactory;
	}
}

如果没有BeanFactoryPostProcessor干预的话，默认初始化完成之后的容器中会有一个processorUser对应的ProcessorUser类型的对象。

但我让下面的PostProcessor生效后就会发现 processorUser对应的对象类型是ProcessorCity了

@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		System.out.println("MyBeanFactoryPostProcessor");
		BeanDefinition processorUser = beanFactory.getBeanDefinition("processorUser");
		processorUser.setBeanClassName("com.jv.spring.postprocessor.entity.ProcessorCity");
	}
}

看debug的情况

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