java Filter的实际应用一例

以下代码为项目期间，使用fiter过滤器控制统一编码和防止非法url进入

package com.tongtech.bjvsp.sysmng.filter;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.tongtech.bjvsp.sysmng.constant.ConstantServlet;

public class EncodingFilter extends HttpServlet implements Filter {
	private FilterConfig filterConfig;

	// Handle the passed-in FilterConfig
	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
	}

	// Process the request/response pair
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain filterChain) {
		try {

			HttpServletRequest httpRequest = (HttpServletRequest) request;
			HttpServletResponse httpResponse = (HttpServletResponse) response;
			boolean isValid = true;
			String uriStr = httpRequest.getRequestURI();
			if (uriStr.indexOf(".jsp") == -1 && uriStr.indexOf(".do") == -1) {
				isValid = true;
			} else if (uriStr.indexOf("login.jsp") == -1 && uriStr.indexOf("login.do") == -1
					&& httpRequest.getSession().getAttribute("UserWraper") == null) {
				isValid = false;
			}

			if (isValid) {
				request.setCharacterEncoding("GBK");
				filterChain.doFilter(request, response);
			}

			else {
				request.setCharacterEncoding("GBK");
				PrintWriter out = httpResponse.getWriter();
				if( uriStr.indexOf("index.jsp") == -1 ) {
					out.write("<script>window.parent.parent.location.href='../../login.jsp'</script>");
				} else {
					out.write("<script>window.parent.parent.location.href='../login.jsp'</script>");
				}

			}

		} catch (ServletException sx) {
			filterConfig.getServletContext().log(sx.getMessage());
		} catch (IOException iox) {
			filterConfig.getServletContext().log(iox.getMessage());
		}
	}

	// Clean up resources
	public void destroy() {
	}
}

out.write内的内容为当未登录时或Session过期时通过地址栏访问应用URL时
对于页面跳转的控制

web.xml配置

<filter>
    <filter-name>encodingfilter</filter-name>
    <filter-class>com.tongtech.bjvsp.sysmng.filter.EncodingFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>encodingfilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

out.write("<script>window.parent.parent.location.href='../../login.jsp'</script>");  
                } else {  
                    out.write("<script>window.parent.parent.location.href='../login.jsp'</script>");  
parent.parent麻不麻烦啊,还有../../login.jsp这是什么和什么啊
这样写感觉不友好,直接跳转到一个含login.jsp链接的错误页面不就好了

看来是 js 不熟啊，用：

window.top.location.href = 【login.jsp的绝对路径】

或者更好（个人认为）：

out.write("<script>\n");
out.write("alert('你没有登录...'); \n");
out.write("window.opener = ''; \n");
out.write("window.close(); \n");
out.write("</script>");

恩你的更好,改好后这个filter收藏了:)
如果不用绝对路径, else {  
                    out.write("<script>window.parent.parent.location.href='../login.jsp'</script>");  
                }  源码这句要删了,只有uriStr.indexOf("index.jsp")==-1才能到这步,根本不存在else

真是晕倒，为何不使用RequestDistpach跳转？就是是使用sendRedirect貌似也比这个要好

楼主这样还是会乱码吧！http传递过来的编码不是GBK的吧，如果不是GBK的话，你直接就将它设置成GBK，是会乱码的。先用ISO-8859-1取出再把它转换成GBK就一定不会的。可能你现在这样也不会乱。乱码的原因是因为我们没有控制好编码的一致性，要转换编码需要人工来完成才会正确的。这个只是我在处理乱码的时候个人理解的。