JSP code MVC programming example

I have never understood the role of JAVABEAN in MVC. Now let's look at an instance.

Define a 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;
}
}

Function of JAVABEAN: it is a PO object that I thought was a VO object. Wrong!

In this way, we can understand that the function of JAVABEAN is actually a thing used to transmit data. In this PHPCMS project, it is equivalent to transmitting a result set. How does the Controller transmit data from the M layer to the view layer for rendering. You can use this method.

Let's look at our Action class.
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.exe cuteUpdate ();

} 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.exe cuteQuery ();
} 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 ();
}
}
}

This class also places database connection operations here. It is actually an incorrect method. The correct method should be to write the database layer to a CLASS separately. But here let's take a look:

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.exe cuteUpdate ();
} Catch (SQLException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
}
Return flag;
}

This DAO object is used to receive data from the JAVABEAN layer.

Let's see how to SET the value to this BEAN.

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); // It depends on the SET and GET methods !!!!
User. setUserPwd (userPwd );
DAO dao = new DAO ();