MVC 实现的小实例

                                                                                                     MVC 实现的小实例

      在上一篇博文中我们搭建了一下开发环境。在这个基础上这一篇文章我们来讲一下mvc的实现，在Java web中开始采用的形式是model （JavaBean+jsp)，但是后来发现这样写的话前后台的耦合度会增加，不利于系统的维护，为了避免牵一发而动全身，所以后来慢慢的诞生了model2（jsp+servlet+javaBean)这样就把前后台的耦合度给降低了,这样的实现是所谓的mvc下面我们来做一个demo;

        step1:在elipse中建立一个java web动态工程,工程名称是mvcDemo，由于时间问题这里做的很简单主要是阐述一下思想：

        step2:建立一个mysql数据库 mvcdb,里边有一张表table1:


       step3:下载mysql-jdbc驱动包    

 下载

         下载之后把这个jar复制到WEB-INF/lib中或者添加到external jar中都可以。

       在工程下新建一个数据库操作类：dbUtils代码如下：

package com.soft.grand.Utils;

import java.util.*;

import java.sql.*;

import com.mysql.jdbc.Connection;

public class dbUtils {
public static String name = "root";
public static String pwd = "root";
public static String driver = "com.mysql.jdbc.Driver";
public static String connUrl = "jdbc:mysql://localhost:3306/mvcdb";
public static Connection conn;
public static Statement statement;
public static ResultSet rs;
public static int isRegist = 0; // 数据库驱动只可以注册一次，这是注册次数

/*
* 构造函数
*/
public dbUtils() {
}

private synchronized static Connection getConnection() {
try {
if (isRegist == 0) {
Class.forName(driver).newInstance();
isRegist = 1;
}
if (conn == null)
conn = (Connection) DriverManager.getConnection(connUrl, name,
pwd);

} catch (Exception e) {
e.printStackTrace();
}
return conn;
}

/*
* 执行修改,删除，插入等操作
*/
public synchronized static int updateOrInsert(String sql) {
int count = 0;
getConnection();
try {
statement = conn.createStatement();
count = statement.executeUpdate(sql);
} catch (Exception e) {
e.printStackTrace();
} finally {

try {
if (statement != null) {
statement.close();
statement = null;
}
if (conn != null) {
conn.close();
conn = null;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return count;
}

/*
* 查询 返回List<map>
*/
public static synchronized List<Map> query(String sql) {
List<Map> list = null;
getConnection();
try {
statement = conn.createStatement();
rs = statement.executeQuery(sql);
if (rs != null) {
ResultSetMetaData data = rs.getMetaData();
int count = data.getColumnCount();
Map map = null;
list = new ArrayList<Map>();
while (rs.next()) {
map = new HashMap();
for (int i = 1; i <= count; i++) {
map.put(data.getColumnName(i), rs.getObject(i));
}
}
list.add(map);

}

} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (statement != null) {
statement.close();
statement = null;
}
if (conn != null) {
conn.close();
conn = null;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return list;

}

/*
* 执行一条语句返回一个object对象
*/
public synchronized static Map getObject(String sql) {
getConnection();
Map map = null;
try {
statement = conn.createStatement();
rs = statement.executeQuery(sql);
while (rs.next()) {
map = new HashMap();
ResultSetMetaData data = rs.getMetaData();
int count = data.getColumnCount();
for (int i = 1; i <= count; i++) {
map.put(data.getColumnName(i), rs.getObject(i));
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (statement != null) {
statement.close();
statement = null;
}
if (conn != null) {
conn.close();
conn = null;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return map;
}

}

tep4:在工程下创建两个jsp（show.jsp,index.jsp）与一个servlet，一个person类：queryInfo代码如下：

package com.soft.grand.Utils;

import java.io.IOException;

import javax.servlet.ServletConfig;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.util.*;

/**

 * Servlet implementation class queryInfo

 */

@WebServlet("/queryInfo")

public class queryInfo extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#HttpServlet()
*/
public queryInfo() {
super();
// TODO Auto-generated constructor stub
}

/**
* @see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException {
// TODO Auto-generated method stub
}

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
*      response)
*/
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doPost(request, response);

}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
*      response)
*/
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub

dbUtils utils = new dbUtils();
String sql = "select * from table1 where id=1";
// String sql="select * from table1";
Map map = null;

map = utils.getObject(sql);
// list=utils.query(sql);
person p = new person();
/*
* Iterator i=list.iterator(); while(i.hasNext()){ Map map=(Map)
* i.next(); System.out.print(map.get("name").toString()); }
*/
p.setName(map.get("name").toString());
p.setSex(map.get("sex").toString());
p.setPhone(map.get("phone").toString());
List list = new ArrayList();
list.add(p);
request.setAttribute("list", list);

request.getRequestDispatcher("/show.jsp").forward(request, response);
}

}

index.jsp:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

    pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">

<title>Insert title here</title>

</head>

<body>

    <form action="queryInfo" method=post"> 

      <input type="submit"/>

    </form>

</body>

</html>

show.jsp:

<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">

<title>Insert title here</title>

</head>

<body>
<div>

<c:forEach var="list" items="${list}">

           ${list.name}

         </c:forEach>

</div>

</body>

</html>

 person:

package com.soft.grand.Utils;

public class person {
private int id;
private String name;
private String sex;
private String phone;

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getSex() {
return sex;
}

public void setSex(String sex) {
this.sex = sex;
}

public String getPhone() {
return phone;
}

public void setPhone(String phone) {
this.phone = phone;
}

}

这几个文件主要逻辑是这样的：首先发布工程index.jsp显示，这个页面会出现一个按钮，点击触发表单进去servlet 然后servlet中与数据库中对接操作，把数据存储在model person中然后在跳转去show.jsp中显示数据，在这里我用到了JSTL 标签，在show.jsp文件的头部可以看到有如下代码：

<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%/>

 换需要导入两个jar包：

   点击下载

下载之后点击工程右键->properties->java build path->libary->add external jar 然后选中你的这来那个包，或者可以直接把这两个包复制到web-inf/lib下就ok

这就是一个简单的mvc 由于时间关系数据库 jsp页面都比较简单  主要是这个思路。