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請給出一個mvc模式編程的實例，最簡單的HelloWord
馬克-to-win：下面我們先給出一個最簡單的mvc例子。這是一個常見的購物車的例子。在下面的例子當中，作為View的add.jsp提交給作為Controller的 ServletHello1.java來處理。真正的處理過程交給了作為Model的Cart.java來處理。作為Controller的 ServletHello1.java，用response.sendRedirect("add.jsp");這句話，最后控制流程跳轉(zhuǎn)到 add.jsp。馬克- to-win：馬克 java社區(qū)：防盜版實名手機尾號： 73203。
例1.1.1：
add.jsp:
<%@ page contentType="text/html; charset=GBK" %>
<html>
<body>
<hr>
<center><h3>書目</h3></center>
<table border="1" width="300" cellspacing="0" cellpadding="3" align="center">
<tr><th>書名</th><th>價格</th></tr>
<tr>
<form action="MarkToWinServlet" method="post">
<td>Java自學</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自學">
<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">看看購物車</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>購物車內(nèi)容</b>
</caption>
<tr>
<th>書名</th>
<th>價格</th>
<th>數(shù)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">接著買</a>
</body>
</html>
MVC模式下訪問數(shù)據(jù)庫
下面的例子給出在mvc模式下如何訪問數(shù)據(jù)庫。
例1.2.1：
<%@ page contentType="text/html; charset=GBK" %>
<html>
<body>
<center><h3>學生登記系統(tǒng)(for 教務(wù)處)</h3></center>
<form action="MarkToWinServlet" method="post">
姓名<INPUT TYPE="TEXT" NAME="name">
年齡<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();
/*即使表為空，rs.getInt(1)返回值為0，我們的程序邏輯也對*/
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的目的是讓ds有值，和con無關(guān)*/
new DatabaseConn();
}
Connection con = null;
con = ds.getConnection();
return con;
}
}
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