📄 cookiecounter.java
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/*程序清单5-8*/
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import sun.servlet.http.Cookie;
public class CookieCounter extends HttpServlet
{
//countername是Servlet保存的主Cookie的名字
private static final String countername = "MyCounter";
/*defaultInitialValue是servlet缺省初试值，是客户与服务器初试的会面值。
在实例中可以被Servlet的初始化参数覆盖*/
static final int defaultInitialValue=10;
//initialValue是实例实际上的初试值
private int initialValue;
//初始化Servlet
public void init(ServletConfig conf) throws ServletException
{
String s;
super.init(conf);
if((s = getInitParameter("initial")) == null)
{
initialValue= defaultInitialValue;
}else
{
try
{
initialValue= Integer.parseInt(s);
}
catch (NumberFormatException e)
{
initialValue = defaultInitialValue;
log("Non-numeric format for 'initial' parameter:" + s);
}
}
}
//处理客户请求
protected void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException.IOException
{
int counter = initialValue;
Cookie Cookies[],c = null;
boolean hadCookies = false, hadCounter = false;
//方法getCookies返回这次请求的所有Cookie
if ((Cookiese = Cookie.getCookies(req))!=null)
{
hadCookies = true;
for (int i=0;i<Cookies.length ;i++ )
{
if (Cookies[i].getName().equals(counterName))
{
try
{
//方法clone返回该Cookie对象的一个拷贝
c = (Cookie)Cookies[i].clone();
counter = Integer.parseInt(c.getValue());
c.setValue(Integer.toString(counter + 1));
hadCounter = true;
}
catch (NumberFormatException e)
{
c = null;
}
break;
}
}
}
/*不管以前有无名字为"MyCounter"的Cookie，现在都要保存它*/
if (c == null)
{
//Cookie的构造函数
c = new Cookie(counterName,Integer.toString(counter));
//给Cookie加注解
c.setComment("Supports Cookie Counter Demo Servlet");
//设定最长保存期限
c.setMaxAge(2*24*60*60);
//设定路径
c.setPath("/");
//保存Cookie
c.saveCookie(res);
}
if (false)
{
//增加一个新的Cookie，在退出浏览器时删除！
c = new Cookie("gensym-"+(System.currentTimeMillis() & 0x0ff),
new Date.toString());
c.setComment("Show multi-Cookies support");
c.saveCookie(res);
}
//产生应答信息，一个显示所有的Cookies、他们的值和属性、以及一些其它信息的HTML
//页面，建立一个长度为4068字节的输出缓冲区。
//建立一个缓冲区
ByteArrayOutputStream bytes;
//建立一个输出流
PrintStream out;
//Cookies的长度限制是4K
bytes = new ByteArrayOutputStream(4096);
//连接输出流与缓冲区
out = new PrintStream(bytes);
out.println("<html><head><title>");
out.println("<Cookie Counter</title></head>");
out.println("<body>");
out.println("<center><h1>Cookie Counter</h1></center>");
if (hadCounter)
{
out.println("<center>");
out.println("<p><em><b>Your session's counter name was");
out.println(counter);
out.println("before you visited this page!</b></em></p>");
out.println("<p>The counter has been incremented.");
out.println("</center>");
}
else
{
out.println("<p>You presented no session Cookie.");
out.println("A new Cookie was created with an initial counter");
out.println("holding the value" + counter + ".");
}
if (hadCookies)
{
out.println("<p>You presented these Cookies:<ol>");
for (int i=0;i<Cookies.length ;i++ )
{
String temp;
out.println("<li>Name = ");
out.println(Cookies[i].getName());
out.println(", Value = ");
out.println(Cookies[i].getValue());
//方法getDomain返回该Cookie的区域
if ((temp = Cookies[i].getName()) != null)
{
out.println(", Domain = ");
out.println(Cookies[i].getDomain());
}
if ((temp = Cookies[i].getPath()) != null)
{
out.println(", Path= ");
out.println(Cookies[i].getPath());
}
}
out.println("</ol>");
}
out.println("<p> Watch teh value of the counter change");
out.println(" as reload this page! The counter is updated");
out.println("by the servlet which dynamically generates");
out.println(" this web page!");
//方法getHeader返回请求的头部信息
String temp = req.getHeader("User-Agent");
out.println("<p> Your browser is <b>"
+ ((temp != null)?temp:"not known!") + "</b>.");
out.println("<p>The cookie server's time is now <b>"
+ new Date() + "</b>.");
out.println("</body></html>");
out.flush();
res.setContentType("text/html");
res.setContentLength(bytes.size());
bytes.writeTo(res.getOutputStream());
}
public String getServletInfo()
{
return "Demonstrates the Cookie API for user sessions!";
}
}
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