loginfilter.java

在sun实训时写的

/*
 * LoginFilter.java
 *
 *
 */

package com.dvd.web;

import com.dvd.model.DVDLibrary;

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

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

import sun.misc.BASE64Decoder;


/**
 *
 * @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 {
        
        if (debug) log("LoginFilter:doFilter()");
        
        HttpServletRequest request = (HttpServletRequest) _request;
        HttpServletResponse response = (HttpServletResponse) _response;
        ServletContext context = filterConfig.getServletContext();
        
        HttpSession session = request.getSession();
        DVDLibrary library = (DVDLibrary) session.getAttribute("library");
        
        doBeforeProcessing(request, response);
        
        Throwable problem = null;
        
        if ( library != null ) {
            try {
                chain.doFilter(request, response);
            } catch(Throwable t) {
                //
                // If an exception is thrown somewhere down the filter chain,
                // we still want to execute our after processing, and then
                // rethrow the problem after that.
                //
                problem = t;
                t.printStackTrace();
            }
        } else {
            // Check if browser is sending the user's credentials
            String credentials = request.getHeader("Authorization");
            if ( credentials != null ) {
                
                // Retrieve the credentials from the header string
                credentials = credentials.substring(6);
                context.log("Credentials = " + credentials);
                

                // Decode the username:password string
                BASE64Decoder decoder = new BASE64Decoder();
                byte[] data = decoder.decodeBuffer(credentials);
                String pair = new String(data);

                // Retrieve the username portion of the credentials
                String username = pair.substring(0, pair.indexOf(':'));
                context.log("Username = " + username);

                // Use the username to create a user-specific
                library = new DVDLibrary(username);
                session.setAttribute("library", library);
                
                // And then proceed with the request
                
                try {
                    chain.doFilter(request, response);
                } catch(Throwable t) {
                    //
                    // If an exception is thrown somewhere down the filter chain,
                    // we still want to execute our after processing, and then
                    // rethrow the problem after that.
                    //
                    problem = t;
                    t.printStackTrace();
                }
                
            } else {
                
                // Send the login challenge
                context.log("Sending the challenge.");
                response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
                response.setHeader("WWW-Authenticate", "Basic realm=dvdLogin");
            }
        }
    }
    
    /**
     * 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;
}