程序开发：MVC设计模式与应用

MVC全名是Model View Controller，是模型(model)－视图(view)－控制器(controller)的缩写，一种软件设计典范，用一种业务逻辑、数据、界面显示分离的方法组织代码，将业务逻辑聚集到一个部件里面，在改进和个性化定制界面及用户交互的同时，不需要重新编写业务逻辑。MVC被独特的发展起来用于映射传统的输入、处理和输出功能在一个逻辑的图形化用户界面的结构中。

下面讲解简单的登录操作:

程序流程图:

JSP的功能

 User.java文件

package com.mvc.oumyye.vo ;/** *  * @author 偶my耶 *    实体类 */public class User {    private String userid ;    private String name ;    private String passWord ;    public void setUserid(String userid){        this.userid = userid ;    }    public void setName(String name){        this.name = name ;    }    public void setPassword(String password){        this.password = password ;    }    public String getUserid(){        return this.userid ;    }    public String getName(){        return this.name ;    }    public String getPassword(){        return this.password ;    }}

DatabaseConnection.java

package com.mvc.oumyye.dbc ;import java.sql.* ;/** *  * @author 偶my耶 *    数据库连接 */public class DatabaseConnection {    private static final String DBDRIVER = "org.gjt.mm.MySQL.Driver" ;     private static final String DBURL = "jdbc:mysql://localhost:3306/mytest" ;    private static final String DBUSER = "root" ;    private static final String DBPASSWORD = "root" ;    private Connection conn = null ;    public DatabaseConnection() throws Exception{        try{            Class.forName(DBDRIVER) ;            this.conn = DriverManager.getConnection(DBURL,DBUSER,DBPASSWORD) ;        }catch(Exception e){            throw e ;        }    }    public Connection getConnection(){        return this.conn ;    }    public void close() throws Exception{        if(this.conn != null){            try{                this.conn.close() ;            }catch(Exception e){                throw e ;            }        }    }}

package com.mvc.oumyye.dao ;import com.mvc.oumyye.vo.User;public interface IUserDAO {        public boolean findLogin(User user) throws Exception ;} 

package com.mvc.oumyye.dao.impl ;import com.mvc.oumyye.dao.*;import com.mvc.oumyye.vo.User;import java.sql.* ;/** *  * @author 偶my耶 *    Dao实现类 */public class UserDAOImpl implements IUserDAO {    private Connection conn = null ;    private PreparedStatement pstmt = null ;    public UserDAOImpl(Connection conn){        this.conn = conn ;    }    public boolean findLogin(User user) throws Exception{        boolean flag = false ;        String sql = "SELECT name FROM user WHERE userid=? AND password=?" ;        this.pstmt = this.conn.prepareStatement(sql) ;        this.pstmt.setString(1,user.getUserid()) ;        this.pstmt.setString(2,user.getPassword()) ;        ResultSet rs = this.pstmt.executeQuery() ;        if(rs.next()){            user.setName(rs.getString(1)) ;                flag = true ;        }        this.pstmt.close() ;        return flag ;    }} 

DAOFactory.java

package com.mvc.oumyye.factory ;import com.mvc.oumyye.dao.*;import com.mvc.oumyye.dao.proxy.*;/** *  * @author 偶my耶 *    工厂接口 */public class DAOFactory {    public static IUserDAO getIUserDAOInstance(){        return new UserDAOProxy() ;    }}

UserDAOProxy.java

package com.mvc.oumyye.dao.proxy ;import com.mvc.oumyye.dbc.DatabaseConnection;import com.mvc.oumyye.dao.IUserDAO;import com.mvc.oumyye.dao.impl.UserDAOImpl;import com.mvc.oumyye.vo.User;/** *  * @author 偶my耶 *    工厂类 实现业务操作 */public class UserDAOProxy implements IUserDAO {    private DatabaseConnection dbc = null ;    private IUserDAO dao = null ;    public UserDAOProxy(){        try{            this.dbc = new DatabaseConnection() ;        }catch(Exception e){            e.printStackTrace() ;        }        this.dao = new UserDAOImpl(dbc.getConnection()) ;    }    public boolean findLogin(User user) throws Exception{        boolean flag = false ;        try{            flag = this.dao.findLogin(user) ;            }catch(Exception e){            throw e ;        }finally{            this.dbc.close() ;        }        return flag ;    }} 

LoginServlet.java

package com.mvc.oumyye.servlet ;import java.io.* ;import java.util.* ;import javax.servlet.* ;import javax.servlet.http.* ;import com.mvc.oumyye.factory.DAOFactory;import com.mvc.oumyye.vo.User;/** *  * @author 偶my耶 *    Servlet */public class LoginServlet extends HttpServlet {        private static final long serialVersionUID = 1L;    public void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{        String path = "login.jsp" ;        String userid = req.getParameter("userid") ;        String userpass = req.getParameter("userpass") ;        System.out.println(userid);        System.out.println(userpass);        List<String> info = new ArrayList<String>() ;            if(userid==null || "".equals(userid)){            info.add("用户名不能为空！！！") ;        }        if(userpass==null || "".equals(userpass)){            info.add("密码不能为空！！") ;        }        if(info.size()==0){                User user = new User() ;            user.setUserid(userid) ;            user.setPassword(userpass) ;            try{                if(DAOFactory.getIUserDAOInstance().findLogin(user)){                    info.add("欢迎" + user.getName() + "登陆") ;                } else {                    info.add("请重新登录") ;                }            }catch(Exception e){                e.printStackTrace() ;            }        }        req.setAttribute("info",info) ;        req.getRequestDispatcher(path).forward(req,resp) ;    }    public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{        this.doGet(req,resp) ;    }}

web.xml文件

<?xml version="1.0" encoding="ISO-8859-1"?><web-app xmlns="http://java.sun.com/xml/ns/javaee"   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"   version="2.5">  <display-name>Welcome to Tomcat</display-name>  <description>     Welcome to Tomcat  </description>    <servlet>        <servlet-name>login</servlet-name>        <servlet-class>            com.mvc.oumyye.servlet.LoginServlet        </servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>login</servlet-name>        <url-pattern>/LoginServlet</url-pattern>    </servlet-mapping></web-app>

login.jsp文件

<%@ page contentType="text/html" pageEncoding="GBK"%><%@ page import="java.util.*"%><html><head><title></title></head><body><script language="Javascript">    function validate(f){        if(!(/^/w{5,15}$/.test(f.userid.value))){            alert("用户ID必须是5~15位！") ;            f.userid.focus() ;            return false ;        }        if(!(/^/w{5,15}$/.test(f.userpass.value))){            alert("密码必须是5~15位！") ;            f.userpass.focus() ;            return false ;        }    }</script><%    request.setCharacterEncoding("GBK") ;%><%    List<String> info = (List<String>) request.getAttribute("info") ;    if(info != null){    // 有信息返回        Iterator<String> iter = info.iterator() ;        while(iter.hasNext()){%>            <h4><%=iter.next()%></h4><%        }    }%><form action="LoginServlet" method="post" onSubmit="return validate(this)">    用户ID：<input type="text" name="userid"><br>    密&nbsp;&nbsp;码：<input type="password" name="userpass"><br>    <input type="submit" value="登陆">    <input type="reset" value="重置"></form></body></html>

数据库文件.sql

/*======================= 创建user数据表 =======================*/CREATE TABLE user(    userid            VARCHAR(30)        PRIMARY KEY ,    name            VARCHAR(30)        NOT NULL ,    password        VARCHAR(32)        NOT NULL) ;/*======================= 插入测试数据 =======================*/INSERT INTO user (userid,name,password) VALUES ('admin','administrator','admin') ;

效果图：

MVC设计模式的好处：