1package com.zj.sample;
 2import java.io.IOException;
 3import java.util.Date;
 4import javax.servlet.Filter;
 5import javax.servlet.FilterChain;
 6import javax.servlet.FilterConfig;
 7import javax.servlet.ServletException;
 8import javax.servlet.ServletRequest;
 9import javax.servlet.ServletResponse;
10import javax.servlet.http.HttpServletRequest;
11 
12public class SimpleFilter1 implements Filter {
13    @SuppressWarnings("unused")
14    private FilterConfig filterConfig;
15 
16    public void init(FilterConfig config) throws ServletException {
17       this.filterConfig = config;
18    }
19 
20    public void doFilter(ServletRequest request, ServletResponse response,
21           FilterChain chain) {
22       try {
23           System.out.println("Within SimpleFilter1:Filtering the Request");
24           HttpServletRequest req = (HttpServletRequest) request;
25           System.out.println(req.getRemoteHost() + " tried to access "
26                  + req.getRequestURL() + " on " + new Date() + ".");
27           chain.doFilter(request, response);
28           System.out.println("Within SimpleFilter1:Filtering the Response");
29       } catch (IOException ioe) {
30           ioe.printStackTrace();
31       } catch (ServletException se) {
32           se.printStackTrace();
33       }
34    }
35 
36    public void destroy() {
37       this.filterConfig = null;
38    }
39}

web.xml設(shè)置不變，同章節(jié)3。
 
測(cè)試：
輸入[url]http://localhost:8080/Test4Jsp/login.jsp[/url]
 
結(jié)果：
Within SimpleFilter1:Filtering the Request...
0:0:0:0:0:0:0:1 tried to access [url]http://localhost:8080/Test4Jsp/login.jsp[/url] on Sun Mar 04 17:01:37 CST 2007.
Within SimpleFilter2:Filtering the Request...
Within SimpleFilter2:Filtering the Response...
Within SimpleFilter1:Filtering the Response...

5．訪問(wèn)時(shí)的過(guò)濾器（在過(guò)濾器中使用servlet初始化參數(shù)）
下面利用init設(shè)定一個(gè)正常訪問(wèn)時(shí)間范圍，對(duì)那些不在此時(shí)間段的訪問(wèn)作出記錄。我們改動(dòng)一下章節(jié)3的SimpleFilter2.java。

 1package com.zj.sample;
 2import java.io.IOException;
 3import java.text.DateFormat;
 4import java.util.Calendar;
 5import java.util.GregorianCalendar;
 6import javax.servlet.Filter;
 7import javax.servlet.FilterChain;
 8import javax.servlet.FilterConfig;
 9import javax.servlet.ServletContext;
10import javax.servlet.ServletException;
11import javax.servlet.ServletRequest;
12import javax.servlet.ServletResponse;
13import javax.servlet.http.HttpServletRequest;
14 
15public class SimpleFilter2 implements Filter {
16    @SuppressWarnings("unused")
17    private FilterConfig config;
18    private ServletContext context;
19    private int startTime, endTime;
20    private DateFormat formatter;
21 
22    public void init(FilterConfig config) throws ServletException {
23       this.config = config;
24       context = config.getServletContext();
25       formatter = DateFormat.getDateTimeInstance(DateFormat.MEDIUM,
26              DateFormat.MEDIUM);
27       try {
28           startTime = Integer.parseInt(config.getInitParameter("startTime"));// web.xml
29           endTime = Integer.parseInt(config.getInitParameter("endTime"));// web.xml
30       } catch (NumberFormatException nfe) { // Malformed or null
31           // Default: access at or after 10 p.m. but before 6 a.m. is
32           // considered unusual.
33           startTime = 22; // 10:00 p.m.
34           endTime = 6; // 6:00 a.m.
35       }
36    }
37 
38    public void doFilter(ServletRequest request, ServletResponse response,
39           FilterChain chain) {
40       try {
41           System.out.println("Within SimpleFilter2:Filtering the Request");
42           HttpServletRequest req = (HttpServletRequest) request;
43           GregorianCalendar calendar = new GregorianCalendar();
44           int currentTime = calendar.get(Calendar.HOUR_OF_DAY);
45           if (isUnusualTime(currentTime, startTime, endTime)) {
46              context.log("WARNING: " + req.getRemoteHost() + " accessed "
47                     + req.getRequestURL() + " on "
48                     + formatter.format(calendar.getTime()));
49              // The log file is under <CATALINA_HOME>/logs.One log per day.
50           }
51           chain.doFilter(request, response);
52           System.out
53                  .println("Within SimpleFilter2:Filtering the Response");
54       } catch (IOException ioe) {
55           ioe.printStackTrace();
56       } catch (ServletException se) {
57           se.printStackTrace();
58       }
59    }
60 
61    public void destroy() {}
62 
63    // Is the current time between the start and end
64    // times that are marked as abnormal access times?
65    private boolean isUnusualTime(int currentTime, int startTime, int endTime) {
66       // If the start time is less than the end time (i.e.,
67       // they are two times on the same day), then the
68       // current time is considered unusual if it is
69       // between the start and end times.
70       if (startTime < endTime) {
71           return ((currentTime >= startTime) && (currentTime < endTime));
72       }
73       // If the start time is greater than or equal to the
74       // end time (i.e., the start time is on one day and
75       // the end time is on the next day), then the current
76       // time is considered unusual if it is NOT between
77       // the end and start times.
78       else {
79           return (!isUnusualTime(currentTime, endTime, startTime));
80       }
81    }
82}

<Logger className="org.apache.catalina.logger.FileLogger" prefix="catalina_log." suffix=".txt" timestamp="true"/>