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用户登录系统的演变之MVC模式

 
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在前面的版本中，jsp中嵌套着java代码，或者调用java 类和方法

显得非常奇怪，层次不够清晰，接下来我们要用mvc模式来完善和优化次系统

Model : java class /java bean/ejb

View： jsp

Controller：Servlet

1,login.jsp

	<body>
		<center><h1>登陆界面</h1>
		<hr>
		<form action="LoginServlet" method="post">
			用户名:
			<input type="text" name="id" />
			<br>
			密&nbsp;&nbsp;码:
			<input type="password" name="passw" />
			<br>
			<input type="submit" value="提交" />
			<input type="reset" value="重置" />
			<hr>
		</form>
		</center>
	</body>
</html>

 

2,LoginServlet.java
package com.dtg.controller;

import java.io.IOException;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.dtg.model.User;
import com.dtg.model.UserCl;

public class LoginServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		/**
		 * 把loginCl.jsp 页面实现的操作，转移到它本应该所在的位置上，就是控制器Servlet
		 * 
		 */
		String id = request.getParameter("id");
		String passw = request.getParameter("passw");
		System.out.println("这是Servlet控制器！！！非常牛逼");
		int pageNow = 1;//当前页
//		int pageSize = 3;//页大小
		int pageCount = 0;//页数
//		int rowCount = 0;//总记录数
		UserCl userCl = new UserCl();
		if (userCl.checkUser(id, passw)) {
			// 用户合法
			/**
			 * sendRedirect “转向” 效率不过，很多软件公司都不适用这个方法，而是使用转发
			 */
			// response.sendRedirect("login_success.jsp");
			
			/**
			 * 在跳转到login_succss.jsp 之前，先把数据准备好 
			 */
			ArrayList<User> al = userCl.getUserByPage(pageNow);
			pageCount = userCl.getPageCount();
//			将al和pageCount,pageNow放入request中
			request.setAttribute("result", al);
			request.setAttribute("pageCount", pageCount+"");
			request.setAttribute("pageNow", "1");
			
			request.getRequestDispatcher("login_success.jsp").forward(request,
					response);
		} else {
//			 用户不合法
			request.getRequestDispatcher("login_failure.jsp").forward(request,
					response);
		}

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		/**
		 * 合二为一
		 * post方法或者get方法都能搞定
		 */
		this.doGet(request, response);

	}

}
 3，login_success.jsp
	<body>
		<center>
			<h1> 
				登陆成功 
			</h1>
			<h2>
				欢迎
				<font color="red"><%=request.getParameter("user")%></font>光临
			</h2>
			<a href="/jsp1/index.jsp">返回重新登录</a>
			<hr>
			<%
				//接受用户想要显示的页面
				String s_pageNow = (String)request.getAttribute("pageNow");
				
				int pageNow = Integer.parseInt(s_pageNow);
			
				//要显示的数据，用request来取
				ArrayList<User> al = (ArrayList<User>)request.getAttribute("result");
				
				//	object -->String -->int
				
				String s_pageCount = (String)request.getAttribute("pageCount");
				int pageCount = Integer.parseInt(s_pageCount);
				
				//用表格显示
				%>
					<table border="1">
							<tr><td>userId</td><td>ID</td><td>PASSWORD</td><td>AGE</td><td>SEX</td></tr>
							<%
								for(int i=0;i<al.size();i++){
									User user = (User)al.get(i);
									%>
										<tr><td><%=user.getUserId() %></td><td><%=user.getId() %></td>
										<td><%=user.getPassword() %></td>
										<td><%=user.getAge() %></td><td><%=user.getSex() %></td></tr>
									<%
								}
							 %>
						</table>
				<%
				//显示超链接
				if(pageNow != 1){
						out.print("<a href=UserServlet?pageNow="+(pageNow-1)+" >上一页</a>");
					}
				
				if(pageNow > 6 && pageNow <= (pageCount-4)){
					for(int i=pageNow-5;i<=pageNow+4;i++){
						out.println("<a href=UserServlet?pageNow="+i+">["+i+"]</a>");
					}
				}else if(pageNow >(pageCount-4) ){
					for(int i=pageCount-9;i<=pageCount;i++){
						out.println("<a href=UserServlet?pageNow="+i+">["+i+"]</a>");
					}
				}else{
					for(int i=1;i<=10;i++){
				//要是pageCount > 10  则不显示全部，只显示前10页的超链接
				//for(int i=1;i<=pageCount;i++)
					out.println("<a href=UserServlet?pageNow="+i+">["+i+"]</a>");
					}
				}
				
				if(pageNow != pageCount){
					out.print("<a href=UserServlet?pageNow="+(pageNow+1)+">下一页</a>");
				}
				
			%>
		</center>

	</body>
</html>
 4，UserServlet.java
package com.dtg.controller;
/*
 * 这个控制器，控制分页，增删改查等功能
 * */
import java.io.IOException;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.dtg.model.User;
import com.dtg.model.UserCl;

public class UserServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		/*
		 * 得到用户希望显示的pageNow
		 * */
		System.out.println("分页也用的是servlet控制器");
		String s_pageNow = request.getParameter("pageNow"); //从login_success.jsp传过来
		try {
			int pageNow = Integer.parseInt(s_pageNow);
			UserCl userCl = new UserCl();
			ArrayList<User> al =  userCl.getUserByPage(pageNow);
			int pageCount = userCl.getPageCount();
			request.setAttribute("result", al);
			request.setAttribute("pageCount", pageCount+"");
			request.setAttribute("pageNow", pageNow+"");
			
			request.getRequestDispatcher("login_success.jsp").forward(request,
					response);
			
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
	}

	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		this.doGet(request, response);

	}

}
 5，UserCl.java
package com.dtg.model;
 
import java.sql.*;
import java.util.ArrayList;
public class UserCl {
	
	Connection conn = null;
	Statement sm = null;
	ResultSet rs = null;
	boolean flag = false;
	
	int pageSize = 3; // 页面大小
	int pageNow = 1;//默认显示第一页
	int rowCount = 0;//总记录数，从数据库中查询
	int pageCount = 0; //页数，(rowCount/pageSize)+1
	
	//关闭连接
	public void closeConn() throws SQLException{
		try {
			if(rs != null){
				rs.close();
				rs = null;
			}
			if(sm!=null){
				sm.close();
				sm = null;
			}
			if(conn!=null){
				conn.close();
				conn = null;
			}
		} catch (Exception e) {
			
			e.printStackTrace();
			// TODO: handle exception
		}
		
	}
	public boolean checkUser(String id, String passw){
		
		try {
			
			ConnDB conndb =new ConnDB();
			conn = conndb.getConn();
			sm = conn.createStatement();
	    	rs = sm
	    			.executeQuery("select password from user2 where id ='" + id
	    					+ "'");
	    	if (rs.next()) {
	    		//确保用户名id是存在的
	    		if (rs.getString(1).equals(passw)) {
	    			//密码正确，用户合法
	    			flag = true;
	    		} else {
	    			//密码不正确，用户不合法
	    			flag = false;
	    		}
	    	} else {
	    		//用户不存在
	    		flag = false;
	    	}
			
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}finally{
			try {
				this.closeConn();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		return flag;
	}
	
	/**
	 * 得到分页的页数
	 * @return
	 */
	public int getPageCount(){
		try {
			conn = new ConnDB().getConn();
			sm = conn.createStatement();
			rs = sm.executeQuery("select count(*) from user2");
			if (rs.next()) {
				rowCount = rs.getInt(1);
			}

			// 计算pageCount
			if (rowCount % pageSize == 0) {
				pageCount = rowCount / pageSize;
			} else {
				pageCount = rowCount / pageSize + 1;
			}
		} catch (Exception e) {
			// TODO: handle exception
		}finally{
			try {
				this.closeConn();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		return pageCount;
	}
	
	/**
	 * 取要分页显示的数据
	 */
	public ArrayList<User> getUserByPage(int pageNow){
		ArrayList<User> al =  new ArrayList<User>();
		try {
			conn = new ConnDB().getConn();
			sm = conn.createStatement();
			rs = sm.executeQuery("select top "+ pageSize+ " * from user2 where userId not in (select top "+ pageSize*(pageNow-1)+" userId from user2 order by userId) order by userId");
			while(rs.next()){
				User user = new User();
				user.setUserId(rs.getInt(1));
				user.setId(rs.getString(2));
				user.setPassword(rs.getString(3));
				user.setAge(rs.getInt(4));
				user.setSex(rs.getString(5));
				
				//添加user到动态数组中
				al.add(user);
			}
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}finally{
			try {
				this.closeConn();
			} catch (Exception e2) {
				e2.printStackTrace();
				// TODO: handle exception
			}
		}
		return al;
	}
}
 6,web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.dtg.controller.LoginServlet</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>TestServlet</servlet-name>
    <servlet-class>com.dtg.controller.TestServlet</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>UserServlet</servlet-name>
    <servlet-class>com.dtg.controller.UserServlet</servlet-class>
  </servlet>



  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>TestServlet</servlet-name>
    <url-pattern>/TestServlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>UserServlet</servlet-name>
    <url-pattern>/UserServlet</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>
 
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