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请给出一个mvc模式编程的实例，最简单的HelloWord
马克-to-win：下面我们先给出一个最简单的mvc例子。这是一个常见的购物车的例子。在下面的例子当中，作为View的add.jsp提交给作为Controller的 ServletHello1.java来处理。真正的处理过程交给了作为Model的Cart.java来处理。作为Controller的 ServletHello1.java，用response.sendRedirect("add.jsp");这句话，最后控制流程跳转到 add.jsp。马克- to-win：马克 java社区：防盗版实名手机尾号： 73203。
例1.1.1：
add.jsp:
<%@ page contentType="text/html; charset=GBK" %>
<html>
<body>
<hr>
<center><h3>书目</h3></center>
<table border="1" width="300" cellspacing="0" cellpadding="3" align="center">
<tr><th>书名</th><th>价格</th></tr>
<tr>
<form action="MarkToWinServlet" method="post">
<td>Java自学</td>
<td>25</td>
<td><input type="submit" name="Submit" value="Add"></td>
<input type="hidden" name="id" value="1">
<input type="hidden" name="title" value="Java自学">
<input type="hidden" name="price" value="25">
</form>
</tr>
<tr>
<form action="MarkToWinServlet" method="post">
<td>C++精通</td>
<td>28</td>
<td><input type="submit" name="Submit" value="Add"></td>
<input type="hidden" name="id" value="2">
<input type="hidden" name="title" value="C++精通">
<input type="hidden" name="price" value="28">
</form>
</tr>
</table>
<a href="cart.jsp">看看购物车</a>
</body>
</html>
package com;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class ServletHello1 extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
Cart cart=(Cart)session.getAttribute("cart");
if(cart==null ) cart = new Cart();
request.setCharacterEncoding("GBK");
String id = request.getParameter("id");
String title = request.getParameter("title");
String price = request.getParameter("price");
cart.addItem(id, title, price);
session.setAttribute("cart", cart);
response.sendRedirect("add.jsp");
}
}
package com;
import java.util.Enumeration;
import java.util.Hashtable;
public class Cart {
protected Hashtable items = new Hashtable();
public void addItem(String itemId, String title, String price) {
String[] item = { itemId, title, price, "1" };
if (items.containsKey(itemId)) {
/* after the next statement,tmpItem is a reference pointing to the
* thing in Hashtable,if you change the thing tmpItem points to, you
* change the thing itself.*/
String[] tmpItem = (String[]) items.get(itemId);
int tmpQuant = Integer.parseInt(tmpItem[3]);
System.out.println("before is " + tmpItem[3]);
tmpQuant++;
tmpItem[3] = Integer.toString(tmpQuant);
String[] tmpItem1 = (String[]) items.get(itemId);
System.out.println("after is " + tmpItem1[3]+tmpItem1[1]);
} else {
items.put(itemId, item);
}
}
public Enumeration getEnumeration() {
return items.elements();
}
}
cart.jsp:
<%@ page contentType="text/html; charset=GBK"%>
<%@ page import="java.util.*"%>
<jsp:useBean id="cart" class="com.Cart" scope="session" />
<html>
<body>
<center>
<table width="300" border="1" cellspacing="0" cellpadding="3"
border="0">
<caption>
<b>购物车内容</b>
</caption>
<tr>
<th>书名</th>
<th>价格</th>
<th>数量</th>
</tr>
<%
Enumeration enu = cart.getEnumeration();
String[] tmpItem;
while (enu.hasMoreElements()) {
tmpItem = (String[]) enu.nextElement();
%>
<tr>
<td align="center"><%=tmpItem[1]%></td>
<td align="center">$<%=tmpItem[2]%></td>
<td align="center"><%=tmpItem[3]%></td>
</tr>
<%
}
%>
</table>
</center>
<a href="add.jsp">接着买</a>
</body>
</html>
MVC模式下访问数据库
下面的例子给出在mvc模式下如何访问数据库。
例1.2.1：
<%@ page contentType="text/html; charset=GBK" %>
<html>
<body>
<center><h3>学生登记系统(for 教务处)</h3></center>
<form action="MarkToWinServlet" method="post">
姓名<INPUT TYPE="TEXT" NAME="name">
年龄<INPUT TYPE="TEXT" NAME="age">
<input type="submit" name="Submit" value="提交">
</form>
</body>
</html>
package com;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ServletHello1 extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("GBK");
String name = request.getParameter("name");
String age = request.getParameter("age");
MyBean mb=new MyBean();
try {
mb.register(name,age);
} catch (Exception e) {
e.printStackTrace();
}
response.sendRedirect("add.jsp");
}
}
package com;
import java.sql.*;
public class MyBean {
public synchronized void register(String name, String age) throws Exception {
Connection con;
/*MysqlConnectionPoolDataSource ds is always in the memory once it is
* created becasue it is static.. */
con = DatabaseConn.getConnection();
Statement stmt = con.createStatement();
/*即使表为空，rs.getInt(1)返回值为0，我们的程序逻辑也对*/
ResultSet rs = stmt.executeQuery("select max(id) from register");
rs.next();
System.out.println(rs.getInt(1));
int id;
id=rs.getInt(1);id++;
String insertString="insert into register Values("+id+",\""+name+"\","+Integer.valueOf(age)+")";
System.out.println(insertString);
stmt.executeUpdate(insertString);
stmt.close();
con.close();
}
}
package com;
import com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSource;
import java.sql.*;
import javax.sql.*;
public class DatabaseConn {
static private MysqlConnectionPoolDataSource ds;
private Connection con;
private DatabaseConn() {
ds = new MysqlConnectionPoolDataSource();
ds.setURL("jdbc:mysql://localhost:3306/test");
ds.setUser("root");
ds.setPassword("1234");
}
public static Connection getConnection() throws Exception {
if (ds == null) {
/*DatabaseConn的目的是让ds有值，和con无关*/
new DatabaseConn();
}
Connection con = null;
con = ds.getConnection();
return con;
}
}
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