Spring中AutowireCapableBeanFactory的使用

今天发现所开发的项目中有这样一段代码：

public class ClickstreamFilter implements Filter {

protected FilterConfig filterConfig;
private MonitorLogger reqMonitorLogger;

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
<span style="white-space:pre">	</span>...
}

/**
* Initializes this filter.
*
* @param filterConfig The filter configuration
* @throws ServletException If an error occurs
*/
public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
<strong><span style="white-space:pre">	</span>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：

/**
* 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：

/**
* 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。