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使用过滤器过滤非法用户时出现的问题，请牛人帮忙

摘要: 使用过滤器过滤非法用户时出现的问题，请牛人帮忙

在网上看到一篇使用过滤器过滤非法用户访问系统网页的方法后，加入到自己的代码中，

出现了其他页面不能访问的问题，并且Index.jsp（首页）中的图片也显示不了，请高人指点，

以下为有关的代码：

Web.xml:
加入


loginFilter
com.tdsj.filter.LoginFilter


loginFilter
/*


LoginFilter.java的源码:

package com.tdsj.filter;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class LoginFilter extends HttpServlet implements Filter {

private FilterConfig filterConfig;

public LoginFilter() {

}

public void init(FilterConfig arg0) throws ServletException {

this.filterConfig = arg0;

}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain filterChain) throws IOException, ServletException {

HttpServletRequest sr = (HttpServletRequest) request;
HttpSession session = sr.getSession(); // 获得session
String user = (String) session.getAttribute("user");

// 判断用户是否登录，如果没有，
if (user == null || user.trim().equals("")) {

// 获锝当前的URL
String strURL = sr.getRequestURL().toString();
System.out.println(strURL);
// 判断是否为index.jsp
if (strURL.indexOf("/Index.jsp") == -1) {

ServletContext sc = filterConfig.getServletContext();
RequestDispatcher rd = sc
.getRequestDispatcher("/Index.jsp");
try {
rd.forward(request, response); // 转发到index.jsp让用户登录
filterChain.doFilter(request, response);
return;
} catch (ServletException sx) {
filterConfig.getServletContext().log(sx.getMessage());
} catch (IOException iox) {
filterConfig.getServletContext().log(iox.getMessage());
}

}
}
filterChain.doFilter(request, response);
}

public void destroy() {

this.filterConfig = null;

}

}

运行后，出现以下错误：

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.IllegalStateException: Cannot forward after response has been committed
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1063)
org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:386)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:229)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
com.tdsj.filter.LoginFilter.doFilter(LoginFilter.java:42)


note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.


请大家帮帮忙

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Cannot forward after response has been committed


RequestDispatcher rd = sc.getRequestDispatcher("/Index.jsp");
不能用这种方式跳转，换成javascript 来跳转就可以了

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楼上说的方法可以试下,二次重复提交请求有时候会阻塞的,还有可以用其它方法!

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Struts里面有个过滤非法用户登录的例子,不如下载Struts源码看看吧!

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djpsunday能不能具体指点一下

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靠。

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doFilter方法写错!
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain filterChain) throws IOException, ServletException {

HttpServletRequest sr = (HttpServletRequest) request;
HttpSession session = sr.getSession(); // 获得session
String user = (String) session.getAttribute("user");

// 判断用户是否登录，如果没有，
if (user == null || user.trim().equals("")) {

String url = sr.getRequestURL().toString();

if (url.indexOf("/index.jsp") == -1) {

RequestDispatcher rd = request
.getRequestDispatcher("/index.jsp");

rd.forward(request, response);

}

} else {

filterChain.doFilter(request, response);
}

}

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public void doFilter(ServletRequest request, ServletResponse response,
FilterChain filterChain) throws IOException, ServletException {

HttpServletRequest sr = (HttpServletRequest) request;
HttpSession session = sr.getSession(); // 获得session
String user = (String) session.getAttribute("user");

// 判断用户是否登录，如果没有，
if (user == null || user.trim().equals("")) {

String url = sr.getRequestURL().toString();

if (url.indexOf("/index.jsp") == -1) {

RequestDispatcher rd = request
.getRequestDispatcher("/index.jsp");

rd.forward(request, response);

return ;

}

} else {

filterChain.doFilter(request, response);
}

}
加一个return;语句!

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以上代码全经过测试!

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还是没有用啊
和上面是一个情况

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你是不是提交form后的问题啊？

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这是对整个web应用的一个过滤！你必须排除form中的action所指向的网页！
可以对程序这样改一下！例如action="do.jsp"
if(url.indexOf("/do.jsp")){

filterChain.doFilter(request,response);

}

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谢谢genzhongzhang

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