关于Filter中的两个异常，重定向后要加Return

- 日理万妓 2022-06-06 06:20 223阅读 0赞

这是个很常见的问题，度娘和谷歌动手就能查到，可是今天还是遇到了，因为一直做业务研发，没有直接关注这些细节。

该文章来自ITeye，网络爬虫请自重！[欢迎大家访问我的博客][Link 1]！

这两个异常如下：

1、Java代码

java.lang.IllegalStateException: Cannot forward after response has been committed  
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:313)  
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)  
        at com.servlet.MyServlet2.doGet(MyServlet2.java:22)  
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)  
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)  
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)  
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
        at com.filter.MyFilter.doFilter(MyFilter.java:48)  
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)  
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:228)  
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)  
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)  
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)  
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)  
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:216)  
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)  
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:634)  
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)  
        at java.lang.Thread.run(Unknown Source)

2、Java 代码

java.lang.IllegalStateException  
        at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:407)  
        at org.apache.catalina.servlets.DefaultServlet.serveResource(DefaultServlet.java:662)  
        at org.apache.catalina.servlets.DefaultServlet.doGet(DefaultServlet.java:325)  
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)  
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)  
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)  
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
        at com.filter.MyFilter.doFilter(MyFilter.java:48)  
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)  
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:228)  
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)  
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)  
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)  
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)  
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:216)  
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)  
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:634)  
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)  
        at java.lang.Thread.run(Unknown Source)

只要在重定向后加return就可以了。

Java代码

public void doFilter(ServletRequest request, ServletResponse response,  
            FilterChain chain) throws IOException, ServletException {  
        request.setCharacterEncoding("UTF-8");  
        response.setCharacterEncoding("UTF-8");       
        HttpServletRequest hrequest = (HttpServletRequest)request;  
        String path = hrequest.getContextPath();  
        String basePath = hrequest.getScheme()+"://"+hrequest.getServerName()+":"+hrequest.getServerPort()+path+"/";  
        // 获得请求的全路径  
        String reUrl = hrequest.getRequestURL().toString();  
        // 是否包含参数  
        int index = reUrl.indexOf("?");  
        String re = "";  
        if(index == -1){  
            re = reUrl.substring(basePath.length());  
        }else{  
            re = reUrl.substring(basePath.length(), index);  
        }  
        // 是否是请求资源  
        if(!isResource(re)){  
            // 是否有访问的权限  
            boolean isCheck = ConnUril.checkUrl(re);  
            if(!isCheck){  
                request.getRequestDispatcher("/error.jsp").forward(request,response);  
                // 必须加返回，否则报错  
                return ;  
            }  
        }  
        // 继续执行  
        chain.doFilter(request, response);  
    }

报错原因很简单，转向后再去执行关于response的操作，就等于执行了两遍转向，因此会报错！

问题简单，也需要留意，再简单的问题也是问题，成功在细节和那些别人以为是傻冒的问题中。

原文网址：[http://cuisuqiang.iteye.com/blog/1478086][http_cuisuqiang.iteye.com_blog_1478086]

[Link 1]: http://cuisuqiang.iteye.com/
[http_cuisuqiang.iteye.com_blog_1478086]: http://cuisuqiang.iteye.com/blog/1478086