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
>
看过一篇资料说，servlet能够与多个客户机连接，接受多个客户的输入，并将结果广播到多个客户机上，例如可以作为一个多人参与的游戏服务器，这点倒是让我挺吃惊的，不知道如何能够实现哪？如果是真的，那servlet是如何得知客户的详细信息的？难道可以象socket那样？不解。。。