Spring中AutowireCapableBeanFactory的使用

今天发现所开发的项目中有这样一段代码：

[java] view
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public class ClickstreamFilter implements Filter {

protected FilterConfig filterConfig;

private MonitorLogger reqMonitorLogger;

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

///

}

/**

* Initializes this filter.

*

* @param filterConfig The filter configuration

* @throws ServletException If an error occurs

*/

public void init(FilterConfig filterConfig) throws ServletException {

this.filterConfig = filterConfig;

WebApplicationContext wac = WebApplicationContextUtils.getWebApplicationContext(filterConfig.getServletContext());

AutowireCapableBeanFactory autowireCapableBeanFactory = wac.getAutowireCapableBeanFactory();

autowireCapableBeanFactory.autowireBeanProperties(this, AutowireCapableBeanFactory.AUTOWIRE_BY_NAME, false);</strong>

}

/**

* Destroys this filter.

*/

public void destroy() {

}

<span style="white-space:pre"> </span>public MonitorLogger getReqMonitorLogger() {

return reqMonitorLogger;

}

public void setReqMonitorLogger(MonitorLogger reqMonitorLogger) {

this.reqMonitorLogger = reqMonitorLogger;

}

}

注意到这里有对AutowireCapableBeanFactory该接口的使用，于是去看了spring的源码：

一段是spring的applicationContext中的代码：

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/**

* Expose AutowireCapableBeanFactory functionality for this context.

* <p>This is not typically used by application code, except for the purpose

* of initializing bean instances that live outside the application context,

* applying the Spring bean lifecycle (fully or partly) to them.

* <p>Alternatively, the internal BeanFactory exposed by the

* {@link ConfigurableApplicationContext} interface offers access to the

* AutowireCapableBeanFactory interface too. The present method mainly

* serves as convenient, specific facility on the ApplicationContext

* interface itself.

* @return the AutowireCapableBeanFactory for this context

* @throws IllegalStateException if the context does not support

* the AutowireCapableBeanFactory interface or does not hold an autowire-capable

* bean factory yet (usually if {@code refresh()} has never been called)

* @see ConfigurableApplicationContext#refresh()

* @see ConfigurableApplicationContext#getBeanFactory()

*/

AutowireCapableBeanFactory getAutowireCapableBeanFactory() throws IllegalStateException;

这里说的意思就是通过getAutowireCapableBeanFactory这个方法将AutowireCapableBeanFactory这个接口暴露给外部使用，AutowireCapableBeanFactory这个接口一般在applicationContext的内部是较少使用的，它的功能主要是为了装配applicationContext管理之外的Bean。

另一段是AutowireCapableBeanFactory该接口中的源码：

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/**

* Autowire the bean properties of the given bean instance by name or type.

* Can also be invoked with {@code AUTOWIRE_NO} in order to just apply

* after-instantiation callbacks (e.g. for annotation-driven injection).

* <p>Does <i>not</i> apply standard {@link BeanPostProcessor BeanPostProcessors}

* callbacks or perform any further initialization of the bean. This interface

* offers distinct, fine-grained operations for those purposes, for example

* {@link #initializeBean}. However, {@link InstantiationAwareBeanPostProcessor}

* callbacks are applied, if applicable to the configuration of the instance.

* @param existingBean the existing bean instance

* @param autowireMode by name or type, using the constants in this interface

* @param dependencyCheck whether to perform a dependency check for object

* references in the bean instance

* @throws BeansException if wiring failed

* @see #AUTOWIRE_BY_NAME

* @see #AUTOWIRE_BY_TYPE

* @see #AUTOWIRE_NO

*/

void autowireBeanProperties(Object existingBean, int autowireMode, boolean dependencyCheck)

throws BeansException;

这个方法的作用就是将传入的第一个参数按照spring中按name或者按type装备的方法将传入的Bean的各个properties给装配上。

再回到我们贴出的第一段code，我们可以看到这是一个Filter的实例，它一般是不在spring的容器中的，而存在于tomcat的容器之中，我不清楚有没有办法使spring来管理tomcat的Beans，但是这里给出了一个很好的办法怎么来用spring装配Filter的instance，。由此想开去，很多component是无法置于spring的容器之中的，这里给出了一个很好的办法来装配这些component。

拥有自动装配能力的BeanFactory。这个BeanFactory并非是要用到应用中去的，在应用中要用，就用BeanFactory或者是 ListableBeanFactory。这个接口更多的作用是用于和其他框架的结合，把不在Spring容器中的Bean加入到Spring容器声明周 期管理中来。

需要注意的是，在Spring的ApplicationContext（Spring的应用容器）中，并没有实现这个接口，因为这个接口在应用中，确实很少用到。

不过，你可以通过ApplicationContext的getAutowireCapableBeanFactory()方法获得。或者，你也可 以实现BeanFactoryAware(这个接口就是为了取得BeanFactory的)，然后把BeanFactory转换成 AutowireCapableBeanFactory