loginfilter.java

在线考试 考生登陆 查分 管理员管理后台等的 的的的的达到的达到的的的

/*
 * LoginFilter.java
 *
 *
 */

package com.eonline.web;



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

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;




/**
 *
 * @author
 * @version
 */

public class LoginFilter implements Filter {
    
    // The filter configuration object we are associated with.  If
    // this value is null, this filter instance is not currently
    // configured.
    private FilterConfig filterConfig = null;
    
    public LoginFilter() {
    }
    
    private void doBeforeProcessing(ServletRequest request, ServletResponse response)
    throws IOException, ServletException {
        if (debug) log("LoginFilter:DoBeforeProcessing");
        //
        // Write code here to process the request and/or response before
        // the rest of the filter chain is invoked.
        //
        
        //
        // For example, a logging filter might log items on the request object,
        // such as the parameters.
        //
        /*
         for (Enumeration en = request.getParameterNames(); en.hasMoreElements(); ) {
             String name = (String)en.nextElement();
             String values[] = request.getParameterValues(name);
             int n = values.length;
             StringBuffer buf = new StringBuffer();
             buf.append(name);
             buf.append("=");
             for(int i=0; i < n; i++) {
                 buf.append(values[i]);
                 if (i < n-1)
                     buf.append(",");
             }
             log(buf.toString());
         }
         */
        
    }
    
    private void doAfterProcessing(ServletRequest request, ServletResponse response)
    throws IOException, ServletException {
        if (debug) log("LoginFilter:DoAfterProcessing");
        //
        // Write code here to process the request and/or response after
        // the rest of the filter chain is invoked.
        //
        
        //
        // For example, a logging filter might log the attributes on the
        // request object after the request has been processed.
        //
        /*
        for (Enumeration en = request.getAttributeNames(); en.hasMoreElements(); ) {
            String name = (String)en.nextElement();
            Object value = request.getAttribute(name);
            log("attribute: " + name + "=" + value.toString());
         
        }
         */
        //
        
        //
        // For example, a filter might append something to the response.
        //
        /*
        PrintWriter respOut = new PrintWriter(response.getWriter());
        respOut.println("<P><B>This has been appended by an intrusive filter.</B>");
         */
    }
    
    /**
     *
     * @param request The servlet request we are processing
     * @param result The servlet response we are creating
     * @param chain The filter chain we are processing
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet error occurs
     */
    public void doFilter(ServletRequest _request, ServletResponse _response,
            FilterChain chain)
            throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest)_request;//;//如果处理HTTP请求，并且需要访问诸如getHeader或getCookies等在ServletRequest中无法得到的方法，就要把此request对象构造成HttpServletRequest
        HttpServletResponse response = (HttpServletResponse)_response;

        String currentURL = request.getRequestURI();//取得根目录所对应的绝对路径:


        String targetURL = currentURL.substring(currentURL.indexOf("/", 1), currentURL.length());  //截取到当前文件名用于比较

        HttpSession session = request.getSession(false);

          if ((!"/login.jsp".equals(targetURL)) && (!"/register.jsp".equals(targetURL))) {//判断当前页是否是重定向以后的登录页面页面，如果是就不做session的判断，防止出现死循环
               if (session == null || session.getAttribute("userItem") == null) {//*用户登录以后需手动添加session
                System.out.println("request.getContextPath()=" + request.getContextPath());
                response.sendRedirect(request.getContextPath() + "/login.jsp");//如果session为空表示用户没有登录就重定向到login.jsp页面
                return;
               }

          }
        //加入filter链继续向下执行
        chain.doFilter(request, response);//.调用FilterChain对象的doFilter方法。Filter接口的doFilter方法取一个FilterChain对象作为它的一个参数。在调用此对象的doFilter方法时，激活下一个相关的过滤器。如果没有另一个过滤器与servlet或JSP页面关联，则servlet或JSP页面被激活。

    }
    
    /**
     * Return the filter configuration object for this filter.
     */
    public FilterConfig getFilterConfig() {
        return (this.filterConfig);
    }
    
    
    /**
     * Set the filter configuration object for this filter.
     *
     * @param filterConfig The filter configuration object
     */
    public void setFilterConfig(FilterConfig filterConfig) {
        
        this.filterConfig = filterConfig;
    }
    
    /**
     * Destroy method for this filter
     *
     */
    public void destroy() {
    }
    
    
    /**
     * Init method for this filter
     *
     */
    public void init(FilterConfig filterConfig) {
        
        this.filterConfig = filterConfig;
        if (filterConfig != null) {
            if (debug) {
                log("LoginFilter:Initializing filter");
            }
        }
    }
    
    /**
     * Return a String representation of this object.
     */
    public String toString() {
        
        if (filterConfig == null) return ("LoginFilter()");
        StringBuffer sb = new StringBuffer("LoginFilter(");
        sb.append(filterConfig);
        sb.append(")");
        return (sb.toString());
        
    }
    
    
    
    private void sendProcessingError(Throwable t, ServletResponse response) {
        
        String stackTrace = getStackTrace(t);
        
        if(stackTrace != null && !stackTrace.equals("")) {
            
            try {
                
                response.setContentType("text/html");
                PrintStream ps = new PrintStream(response.getOutputStream());
                PrintWriter pw = new PrintWriter(ps);
                pw.print("<html>\n<head>\n<title>Error</title>\n</head>\n<body>\n"); //NOI18N
                
                // PENDING! Localize this for next official release
                pw.print("<h1>The resource did not process correctly</h1>\n<pre>\n");
                pw.print(stackTrace);
                pw.print("</pre></body>\n</html>"); //NOI18N
                pw.close();
                ps.close();
                response.getOutputStream().close();;
            }
            
            catch(Exception ex){ }
        } else {
            try {
                PrintStream ps = new PrintStream(response.getOutputStream());
                t.printStackTrace(ps);
                ps.close();
                response.getOutputStream().close();;
            } catch(Exception ex){ }
        }
    }
    
    public static String getStackTrace(Throwable t) {
        
        String stackTrace = null;
        
        try {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            t.printStackTrace(pw);
            pw.close();
            sw.close();
            stackTrace = sw.getBuffer().toString();
        } catch(Exception ex) {}
        return stackTrace;
    }
    
    public void log(String msg) {
        filterConfig.getServletContext().log(msg);
    }
    
    private static final boolean debug = true;
}