out.println(\ out.println(\
HttpSession session=request.getSession(true); //获取客户的会话对象 String item =request.getParameter(\称。
session.removeAttribute(item); //删除商品。 //将购物车中的商品显示给客户：
out.println(\ Enumeration enum=session.getAttributeNames(); while(enum.hasMoreElements())
{ String name=(String)enum.nextElement();
out.print(\ } }
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { doPost(request,response); } }
7.8.3 猜数字
在第3章、第6章讲述JSP内置对象以及javabeans时，曾分别举过猜数字的例子。在这里，我们再使用servlet来实现猜数字这个小游戏，这样，我们就用3种方式实现了这个小游戏：直接由JSP页面来实现、通过javabeans来实现、通过servlet来实现。
当客户访问servlet：GetNumber时，随机分配给客户一个1到100之间的数，然后将这个数字存在客户的session对象中。客户在表单里输入一个数，来猜测分配给自己的那个数字。客户输入一个数字后，提交给servlet：Result，该servlet负责判断这个数是否和客户的session对象中存放的那个数字相同，如果相同就连接到servlet：Success；如果不相同就连接到servlet： Large或Small。然后，客户在这些servlet中重新提交数字到Result。
servlet源文件 GetNumber.java： import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*;
public class GetNumber extends HttpServlet
{ public void init(ServletConfig config) throws ServletException {super.init(config);
46
}
public void doPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException { response.setContentType(\
ServletOutputStream out=response.getOutputStream();
out.print(\ HttpSession session=request.getSession(true); session.setAttribute(\
int number=(int)(Math.random()*100)+1; //获取一个随机数。 session.setAttribute(\ out.print(\ out.print(\ out.print(\ out.print(\ }
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException { doPost(request,response); } }
Result.java： import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*;
public class Result extends HttpServlet
{ public void init(ServletConfig config) throws ServletException {super.init(config); }
public void doPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException { response.setContentType(\
ServletOutputStream out=response.getOutputStream(); HttpSession session=request.getSession(true);
47
String str=request.getParameter(\ if(str==null) {str=\ }
int guessNumber=Integer.parseInt(str);
Integer integer=(Integer)session.getAttribute(\ int realnumber=integer.intValue(); if(guessNumber==realnumber)
{ int n=((Integer)session.getAttribute(\ n=n+1;
session.setAttribute(\ response.sendRedirect(\ }
else if(guessNumber>realnumber)
{ int n=((Integer)session.getAttribute(\ n=n+1;
session.setAttribute(\ response.sendRedirect(\ }
else if(guessNumber { int n=((Integer)session.getAttribute(\ n=n+1; session.setAttribute(\ response.sendRedirect(\ } } public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { doPost(request,response); } } Larger.java： import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; 48 public class Larger extends HttpServlet { public void init(ServletConfig config) throws ServletException {super.init(config); } public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { response.setContentType(\ ServletOutputStream out=response.getOutputStream(); out.print(\。 out.print(\ost name=form>\ out.print(\ out.print(%ubmit value=Enter>\ out.print(\ } public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { doPost(request,response); } } Smaller.java import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class Smaller extends HttpServlet { public void init(ServletConfig config) throws ServletException {super.init(config); } public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { response.setContentType(\ ServletOutputStream out=response.getOutputStream(); out.print(\ 49 out.print(\ out.print(\ out.print(\ out.print(\ } public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { doPost(request,response); } } Success.java import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class Success extends HttpServlet { public void init(ServletConfig config) throws ServletException {super.init(config); } public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { response.setContentType(\ ServletOutputStream out=response.getOutputStream(); HttpSession session=request.getSession(true); int count=((Integer)session.getAttribute(\ int num=((Integer)session.getAttribute(\ long startTime=session.getCreationTime(); long endTime=session.getLastAccessedTime(); long spendTime=(endTime-startTime)/1000; out.println(\ out.println(\ out.println(\ out.println(\ } 50
Java - Servlet入门教程
