Demo of MVC mode in JSP

 

What is the MVC pattern... Let's talk about its process.

 

A form is defined in login. jsp: <form action = "Controller" name = "loginForm" method = "post">

 

This completes the entry from layer V to layer C.

 

 

Controller. java is a Servlet. to inherit from HttpServlet, you must first arrange it in the configuration file. The code is:

 

String id = request. getParameter ("userId ");

String name = request. getParameter ("userName ");

/// Use the model (UserBeanDL) to process the user

/// 1. Create a UserBean processing object

UserBeanDL ubd = new UserBeanDL ();

Try {

Int iId = Integer. parseInt (id );

If (ubd. checkUser (iId, name )){

System. out. println ("control via Servlet ");

/// When you jump to the wel. jsp page, prepare the data to be displayed.

ArrayList al = ubd. getUsersByPage (1 );

Int pageCount = ubd. getPageCount ();

//// Pass the parameter. Here, an ArrayList is passed.

 

Request. setAttribute ("result", al );

 

//// Note: The following parameters are objects. You need to set int --> Object (String)

 

Request. setAttribute ("pageCount", pageCount + "");

 

/// Turn

// Response. sendRedirect ("welcom. jsp ");

/// Because the sendRedirect method is inefficient, it is a common forwarding method in software companies.

/// This method is efficient, and objects in the request can also be used on the next page.

Request. getRequestDispatcher ("threedown/welcome. jsp"). forward (request, response );

} Else {

Request. getRequestDispatcher ("three/login. jsp"). forward (request, response );

}

......

 

 

In UserBean., all operations on the database are as follows:

 

Public class UserBeanDL {

Connection conn = null;

PreparedStatement ps = null;

ResultSet rs = null;

Private int pageCount = 0;

Int pageSize = 3;

Int rowCount = 0;

//// Close the resource

//// Obtain the total number of rows

//// Get pageCount

/// // Add (over)

//// Modify (over)

//// Delete

/// // Search

//// Verify whether the user exists

 

UserBean. java is an entity class.

 

 

In Welcome. jsp:

 

<Tr> <td> ID </td> <td> name </td> <td> age </td> </tr>

<%

Int pageNow = 1;

String szPageNow = request. getParameter ("pageNow ");

If (szPageNow! = Null)

{

PageNow = Integer. parseInt (szPageNow );

}

ArrayList al = (ArrayList) request. getAttribute ("result ");

For (int I = 0; I <al. size (); I ++)

{

UserBean ub = (UserBean) al. get (I );

%>

<Tr> <td> <% = ub. getId () %> </td>

<Td> <% = ub. getName () %> </td>

<Td> <% = ub. getAge () %> </td> </tr>

<%

}

/// From object --> string -- int

Int pageCount = Integer. parseInt (String) request. getAttribute ("pageCount "));

// Int pageCount = ubd. getPageCount ();

For (int I = 1; I <pageCount; I ++ ){

%>

<A href = UserDL? PageNow = <% = I % >><%= I % >></a>

<%

} Www.2cto.com

%>

</Table>

 

UserDL. java is a Servlet dedicated for paging

 

Public void doPost (HttpServletRequest request, HttpServletResponse response)

Throws ServletException, IOException {

System. out. println ("Paging through Servlet ");

String s_pageNow = request. getParameter ("pageNow ");

UserBeanDL ubd = new UserBeanDL ();

Try {

Int pageNow = Integer. parseInt (s_pageNow );

ArrayList al = ubd. getUsersByPage (pageNow );

Int pageCount = ubd. getPageCount ();

Request. setAttribute ("pageNow", pageNow );

Request. setAttribute ("result", al );

Request. setAttribute ("pageCount", pageCount + "");

Request. getRequestDispatcher ("threedown/welcome. jsp"). forward (request, response );

} Catch (Exception e ){

E. printStackTrace ();

}

}

 

Excerpted from the column of wandering Xiaoqi