Java - Servlet入门教程 

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);

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}

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);

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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.*;

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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(\

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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(\ }

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