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 {
    	...
    }

    /**
     * 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);
    }

    /**
     * Destroys this filter.
     */
    public void destroy() {
    }

	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.
	 * 
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.
	 * 
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).
	 * 
Does not 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。