jsp/servlet/javaBean三层架构小示例

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 在java代码中写文档（html)，这是servlet;在文档中写java代码，这是jsp;而如何将两者分开，这就是MVC模式了。虽然是java的一小步，却是程序员们生活的一大步哦。
下面给出一个简单的用户登陆功能，采用jsp/servelt/javaBean来实现MVC模式（即经典的模式2）。

模型层：
package com.vitamin.DataAccess;


import java.sql.*;

public class DBbase {
String sDBDriver = "sun.jdbc.odbc.JdbcOdbcDriver";
String sConnstr = "jdbc:odbc:myDB";
Connection connect = null;
ResultSet rs = null;
Statement stmt = null;


public DBbase()
{

try
{

Class.forName(sDBDriver);

}
catch(ClassNotFoundException ex)
{
System.err.println(ex.getMessage());

}
}
public ResultSet executeQuery(String sql)
{

try
{
this.connect = DriverManager.getConnection(sConnstr);
this.stmt = this.connect.createStatement();
rs = stmt.executeQuery(sql);
}
catch(SQLException ex)
{
System.err.println(ex.getMessage());
}
return rs;
}
public int executeUpdate(String sql)
{
int result = 0;
try
{
this.connect = DriverManager.getConnection(sConnstr);
this.stmt = this.connect.createStatement();
result = stmt.executeUpdate(sql);
}
catch(SQLException ex)
{
System.err.println(ex.getMessage());
}
return result;
}

}


控制层：
package com.vitamin.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.vitamin.DataAccess.*;
import java.sql.*;

public class Hello extends HttpServlet {

/**
* Constructor of the object.
*/
public Hello() {
super();
}

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
 }

/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("text/html");

PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
 out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print(" This is ");
out.print(this.getClass());
out.println(", using the GET method");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}

/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("text/html");
response.setCharacterEncoding("GBK");
PrintWriter out = response.getWriter();

request.setCharacterEncoding("GBK");
String name = request.getParameter("name");
String pwd = request.getParameter("password");
DBbase myDb = new DBbase();
ResultSet rs = null;
int result = 0;

String sql = "select count(*) as count from users where username = '"+name+"' and password = '"+pwd+"'";

try
{
rs = myDb.executeQuery(sql);
if(rs.next())
{
result = rs.getInt("count");
}
}
catch(SQLException ex)
{
ex.printStackTrace();

}

if(result>0)
{
out.println("合法用户");
}
else
{
out.println("非法用户");
}

}

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occure
*/
public void init() throws ServletException {
// Put your code here
 }

}

Web表示层:

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>

<%
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 'index.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>
<FORM name="form1" method="POST" action="/servletTest/servlet/Hello">
<P> &nbsp; 用户名：&nbsp; &nbsp; <INPUT type="text" name="name" maxlength="20" /></P>
<P> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;密码 &nbsp;<INPUT type="password" name="password" maxlength="20" /> </P>
<P>
&nbsp;
</P>
<P> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;<INPUT type="Submit" name="button4" value="确定" /> &nbsp; &nbsp;<INPUT type="Reset" name="button5" value="重置"></P>
<P>
&nbsp;
</P>
<P>
&nbsp;
</P>
</FORM>
</body>
</html>

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