JSP代碼 MVC編程開發實例

我之前一直搞不明白JAVABEAN在MVC中到底充當一個什麼角色。現在來看一個實例

定義一個JAVABEAN
package com.bean;
public class User {
    private String userName;
    private String userPwd;
    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPwd() {
        return userPwd;
    }

    public void setUserPwd(String userPwd) {
        this.userPwd = userPwd;
    }
}

JAVABEAN的作用：是一個PO對象之前我以為是VO對象。搞錯了！

恩我們可以這樣來理解JAVABEAN的作用其實就是用來傳遞數據的一個東西。在我們這次PHPCMS項目中相當於一個結果集的傳輸。控制器接收到一個來自M層的數據之後如何傳遞到視圖層作渲染處理。可以依據這樣的方式。

再來看我們的Action類
package com.dao;
import java.sql.*;
import com.bean.User;
public class DAO {
    Connection conn = null;
    Statement stmt = null;
    ResultSet rs = null;
    PreparedStatement pstmt = null
    public DAO(){
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = getConnection();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public Connection getConnection(){
        String url = "jdbc:mysql://localhost:3306/person";
        String user = "root";
        String password = "123456";
        try {
            conn = DriverManager.getConnection(url, user, password);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }

    public int addPerson(User user){
        int flag = 0;
        String sql = "insert into user(user_name,user_pwd) values(?,?)";
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUserName());
            pstmt.setString(2, user.getUserPwd());
            flag = pstmt.executeUpdate();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return flag;
    }

    public ResultSet showPerson(){
        String sql = "select * from user";
        try {
            pstmt = conn.prepareStatement(sql);
            rs = pstmt.executeQuery();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return rs;
    }

    public void close(){
        try {
            if(rs!=null)rs.close();
            if(pstmt!=null)pstmt.close();
            if(conn!=null)conn.close();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

這個類把數據庫連接操作也放在這裡了。其實是不正確的處理方式。正確的方式應當是將數據庫層單獨寫到一個CLASS類裡面去。但這裡面我們來看一下：

public int addPerson(User user){
        int flag = 0;
        String sql = "insert into user(user_name,user_pwd) values(?,?)";
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUserName());
            pstmt.setString(2, user.getUserPwd());
            flag = pstmt.executeUpdate();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return flag;
    }

這個DAO對象它的作用是接收來自JAVABEAN層的數據。

再看是如何SET值到這個BEAN的

package com.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.bean.User;
 import com.dao.DAO;
 public class AddUser extends HttpServlet {
 public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        String userName = request.getParameter("userName");
        String userPwd = request.getParameter("userPwd");
        User user = new User();
        user.setUserName(userName);//依據的是SET與GET方式了吧！！！！
        user.setUserPwd(userPwd);
        DAO dao = new DAO();