Java之Interceptor和Filter

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最近研究了下Spring的HandlerInterceptor和Java的Filter，因为经常搞混它们两个，今天整理个笔记记录一下。

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HandlerInterceptor 是Spring里面的拦截器

Filter是Java里面的过滤器

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共同点 还是贴下Java里面的注释吧，解释还是很到位的：

?* <p>A HandlerInterceptor gets called before the appropriate HandlerAdapter

?* triggers the execution of the handler itself. This mechanism can be used

?* for a large field of preprocessing aspects, e.g. for authorization checks,

?* or common handler behavior like locale or theme changes. Its main purpose

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?* is to allow for factoring out repetitive handler code.

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?* <p>HandlerInterceptor is basically similar to a Servlet 2.3 Filter, but in

?* contrast to the latter it just allows custom pre-processing with the option

?* of prohibiting the execution of the handler itself, and custom post-processing.

?* Filters are more powerful, for example they allow for exchanging the request

?* and response objects that are handed down the chain. Note that a filter

?* gets configured in web.xml, a HandlerInterceptor in the application context.

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?* <p>As a basic guideline, fine-grained handler-related preprocessing tasks are

?* candidates for HandlerInterceptor implementations, especially factored-out

?* common handler code and authorization checks. On the other hand, a Filter

?* is well-suited for request content and view content handling, like multipart

?* forms and GZIP compression. This typically shows when one needs to map the

?* filter to certain content types (e.g. images), or to all requests.

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? 解释下吧：

? HandlerInteceptor一般用于权限验证，以及一些处理风格本地化等公共代码。

? Filter一般用于修改请求内容和界面的解析处理相关。

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? Inteceptor的三个方法：

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//做实际的请求之前调用
//返回true会接着链式调用
//返回false终止链式调用
boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
	    throws Exception;


//请求之后，解析视图界面之前调用
void postHandle(
			HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
			throws Exception;

//解析完界面之后调用
void afterCompletion(
			HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
			throws Exception;

// 在applicationContext.xml中配置
    <!--interceptors begin-->
    <mvc:interceptors>
        <bean class="com.xxx.AllInterceptor"/>
    </mvc:interceptors>
    <!--interceptors end-->

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? ? Filter配置

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@Component
public class RequestLogFilter implements Filter{

	@Override
	public void destroy() {
		System.out.println("destory");
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// TODO Auto-generated method stub
		System.out.println("doFilter");
		chain.doFilter(request , response);
		
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		// TODO Auto-generated method stub
		System.out.println("init");
		
	}

}


// web.xml配置
<filter>
    <filter-name>testFilter</filter-name>
    <filter-class>com.abcd.system.RequestLogFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>testFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

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? ?测试结果顺序：发现filter会在前面处理

? ?init

? ?doFilter

? ?preHandle

? ?postHandle

? ?afterCompletion

原文：http://labreeze.iteye.com/blog/2213653