Servlet学习以及使用
近期任务安排
今天的内容是继续理解昨天的CRUD的写法，然后采用类似的方法重写猜数字的游戏，以巩固认知。今天是最后一次集中练习javaweb的内容了。
上午我讲一下反射的基本内容，在马士兵的视频里有相关章节。
明天我们就按照类似现在的crud的模式，结合反射和xml操作，自己写一个简单的mvc框架。
后天就正式开始学习struts2.
今天主要使用Servlet重新写了猜数字游戏：
自己写的源代码：
List.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>欢迎进入猜数字游戏</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<div align=center><h1>NumberGuess</h1></div>
<p></p>
<p></p>
<hr width=80%>
<div align="center"><a href="<%=request.getContextPath() %>/NumberGuessServlet?act=NewGuess">新游戏</a></div>
<div align=center>
<form name=f action="<%=request.getContextPath() %>/NumberGuessServlet?act=guess" method="post">
<input type="text" size=8 name="number">
<input type="submit" value="guess">
</form>
</div>
</body>
</html>
Result.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'result.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<div align=center><P>结果显示</P></div>
<p></p>
<p></p>
<hr width="80%"></hr>
<div align=center>${content }</div>
<div align=center> 你总共猜了${GuessTimes }次</div>
<div align=center>总共有${times}人玩过此游戏</div>
<div align=center><a href='<%=request.getContextPath()%>/NumberGuessServlet?act=new'>返回重新猜</a></div>
</body>
</html>
Servlet文件：
NumberGuessServlet1.java（此servlet写的繁琐了）
package com.yuqiao.qiu;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class NumberGuessServlet1 extends HttpServlet {
public NumberGuessServlet1(){
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException{
// request.getSession().removeAttribute("randomNo");
String act=request.getParameter("act");
// Integer randomNo1=(Integer)request.getSession().getAttribute("randomNo");
if(null==request.getSession().getAttribute("randomNo")||"NewGuess".equals(act))
{
Random random=new Random();
Integer randomNo=random.nextInt(101);
System.out.print(randomNo);
request.getSession().removeAttribute("GuessTimes");
request.getSession().setAttribute("randomNo", randomNo);
if(null==this.getServletContext().getAttribute("times")){
this.getServletContext().setAttribute("times", 0);
}
else{
Integer times=(Integer)this.getServletContext().getAttribute("times");
++times;
this.getServletContext().setAttribute("times",times);
}
if("NewGuess".equals(act))
{
// this.getServletContext().setAttribute("times",times);
request.getRequestDispatcher("/list.jsp").forward(request, response);
}
}
if("guess".equals(act))
{
Integer number=Integer.parseInt(request.getParameter("number").trim());
request.getSession().setAttribute("number", number);
Integer GuessTimes=(Integer)request.getSession().getAttribute("GuessTimes");
if(GuessTimes == null)GuessTimes = 0;
GuessTimes+=1;
request.getSession().setAttribute("GuessTimes", GuessTimes);
if(number<(Integer)request.getSession().getAttribute("randomNo")){
request.setAttribute("content", "对不起你猜的数字小了");
}
if(number>(Integer)request.getSession().getAttribute("randomNo")){
request.setAttribute("content", "对不起你猜的数字大了");
}
if(number==(Integer)request.getSession().getAttribute("randomNo")){
// request.getSession().setAttribute("number", number);
request.getSession().removeAttribute("randomNo");
request.setAttribute("content", "恭喜你，你猜对了");
}
request.getRequestDispatcher("/result.jsp").forward(request, response);
}
if("new".equals(act))
{
request.getRequestDispatcher("/list.jsp").forward(request, response);
}
}
@Override
// protected void service(HttpServletRequest request, HttpServletResponse response)
// throws ServletException, IOException {
//
// }
//
// public Integer StringToInt(String number)
// {
// return Integer.parseInt(number);
// }
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
public void init() throws ServletException {
// Put your code here
}
}
Web.xml配置文件
<servlet>
<servlet-name>NumberGuessServlet</servlet-name>
<servlet-class>com.yuqiao.qiu.NumberGuessServlet1</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>NumberGuessServlet</servlet-name>
<url-pattern>/NumberGuessServlet</url-pattern>
</servlet-mapping>
其中写的时候遇到的问题挺多：
1. 对于Servlet路径的问题！（超链接如何链接到servlet，还有request.getRequestDispatcher(路径).farward();的路径问题）
2. 其中超链接是使用doGet（）方式提交的 所以要重写doGet（）方法，不然会报错。
doGet（）方法里面直接调用doPost（）方法。
3. 出现java.lang.IllegalStateException: Cannot forward after response has been committed 错误。主要原因是进行了两次转向。
4.其他都是小问题（就不写了）
今天的内容是继续理解昨天的CRUD的写法，然后采用类似的方法重写猜数字的游戏，以巩固认知。今天是最后一次集中练习javaweb的内容了。
上午我讲一下反射的基本内容，在马士兵的视频里有相关章节。
明天我们就按照类似现在的crud的模式，结合反射和xml操作，自己写一个简单的mvc框架。
后天就正式开始学习struts2.
今天主要使用Servlet重新写了猜数字游戏：
自己写的源代码：
List.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>欢迎进入猜数字游戏</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<div align=center><h1>NumberGuess</h1></div>
<p></p>
<p></p>
<hr width=80%>
<div align="center"><a href="<%=request.getContextPath() %>/NumberGuessServlet?act=NewGuess">新游戏</a></div>
<div align=center>
<form name=f action="<%=request.getContextPath() %>/NumberGuessServlet?act=guess" method="post">
<input type="text" size=8 name="number">
<input type="submit" value="guess">
</form>
</div>
</body>
</html>
Result.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'result.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<div align=center><P>结果显示</P></div>
<p></p>
<p></p>
<hr width="80%"></hr>
<div align=center>${content }</div>
<div align=center> 你总共猜了${GuessTimes }次</div>
<div align=center>总共有${times}人玩过此游戏</div>
<div align=center><a href='<%=request.getContextPath()%>/NumberGuessServlet?act=new'>返回重新猜</a></div>
</body>
</html>
Servlet文件：
NumberGuessServlet1.java（此servlet写的繁琐了）
package com.yuqiao.qiu;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class NumberGuessServlet1 extends HttpServlet {
public NumberGuessServlet1(){
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException{
// request.getSession().removeAttribute("randomNo");
String act=request.getParameter("act");
// Integer randomNo1=(Integer)request.getSession().getAttribute("randomNo");
if(null==request.getSession().getAttribute("randomNo")||"NewGuess".equals(act))
{
Random random=new Random();
Integer randomNo=random.nextInt(101);
System.out.print(randomNo);
request.getSession().removeAttribute("GuessTimes");
request.getSession().setAttribute("randomNo", randomNo);
if(null==this.getServletContext().getAttribute("times")){
this.getServletContext().setAttribute("times", 0);
}
else{
Integer times=(Integer)this.getServletContext().getAttribute("times");
++times;
this.getServletContext().setAttribute("times",times);
}
if("NewGuess".equals(act))
{
// this.getServletContext().setAttribute("times",times);
request.getRequestDispatcher("/list.jsp").forward(request, response);
}
}
if("guess".equals(act))
{
Integer number=Integer.parseInt(request.getParameter("number").trim());
request.getSession().setAttribute("number", number);
Integer GuessTimes=(Integer)request.getSession().getAttribute("GuessTimes");
if(GuessTimes == null)GuessTimes = 0;
GuessTimes+=1;
request.getSession().setAttribute("GuessTimes", GuessTimes);
if(number<(Integer)request.getSession().getAttribute("randomNo")){
request.setAttribute("content", "对不起你猜的数字小了");
}
if(number>(Integer)request.getSession().getAttribute("randomNo")){
request.setAttribute("content", "对不起你猜的数字大了");
}
if(number==(Integer)request.getSession().getAttribute("randomNo")){
// request.getSession().setAttribute("number", number);
request.getSession().removeAttribute("randomNo");
request.setAttribute("content", "恭喜你，你猜对了");
}
request.getRequestDispatcher("/result.jsp").forward(request, response);
}
if("new".equals(act))
{
request.getRequestDispatcher("/list.jsp").forward(request, response);
}
}
@Override
// protected void service(HttpServletRequest request, HttpServletResponse response)
// throws ServletException, IOException {
//
// }
//
// public Integer StringToInt(String number)
// {
// return Integer.parseInt(number);
// }
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
public void init() throws ServletException {
// Put your code here
}
}
Web.xml配置文件
<servlet>
<servlet-name>NumberGuessServlet</servlet-name>
<servlet-class>com.yuqiao.qiu.NumberGuessServlet1</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>NumberGuessServlet</servlet-name>
<url-pattern>/NumberGuessServlet</url-pattern>
</servlet-mapping>
其中写的时候遇到的问题挺多：
1. 对于Servlet路径的问题！（超链接如何链接到servlet，还有request.getRequestDispatcher(路径).farward();的路径问题）
2. 其中超链接是使用doGet（）方式提交的 所以要重写doGet（）方法，不然会报错。
doGet（）方法里面直接调用doPost（）方法。
3. 出现java.lang.IllegalStateException: Cannot forward after response has been committed 错误。主要原因是进行了两次转向。
4.其他都是小问题（就不写了）