关于Filter中的两个异常，重定向后要加Return
编程技术 / houtizong 发布于 3年前 172
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。
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这两个异常如下：
java.lang.IllegalStateException: Cannot forward after response has been committedat 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)
java.lang.IllegalStateExceptionat 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。
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。
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