J2EE to .NET Migration: Quick Tips

Vivek Devarajan
18y
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Here are some Quick tips to get you started, in case you need to migrate a J2EE based application to a .NET based application.

We approach the migration tier wise. Firstly, a technology mapping between both the platforms

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Service/Feature	.NET	J2EE
GUI	WinForms	SWING / AWT
Web GUI	ASP/ASP.NET	JSP
Web Scripting	ISAPI, HttpHandler	Servlet, Filter, HttpModule
Server Side Business Logic Component	Serviced Component (COM+)	EJB Session Beans
Server Side Data Component	Server components with DB logic	EJB BMP Entity Beans with DB Logic
Naming	ADSI	JNDI
Remote Invocation	.NET Remoting	RMI / RMI-IIOP
Data Access	ADO.NET	JDBC, SQL/J
Messaging	MSMQ	JMS
Transactions	COM+ / MTS	JTA

Highlights of the migration strategy

Presentation Tier JSP -> ASP.NET
Business Logic Tier EJB -> COM+ (.NET Enterprise Service)
Data Access Tier JDO/JDBC -> ADO.NET

1. Presentation tier migration

a) JSP -> ASP.NET (sample code snippets) :-

JSP Scriptlet :-

<%for (int i=0;i<3;i++){
out .println(i+"<br>" );
}
%>

ASP .NET scriptlet :-

<% for(int i=0; i<3; i++){
Response.Write(i +"<br>"); }
%>

JSP Expression :-

<%=new java.math.BigDecimal(10.1).negate()%>

ASP .NET Expression :-

<%=System.Decimal.Negate(new System.Decimal(10.1))%>

JSP Declaration :-

<%!
public String foo(){
return "foo";
}
%>

ASP .NET Declaration :-

b) Implicit objects :-

JSP	ASP .NET
application	Application
session	Session
request	Request
response	Response
out	Response.Write

c) Cookies :-

Creating a cookie and setting its expiry time.

Code in J2EE :-

<%
Cookie userCookie = new Cookie("user", "uid123");
userCookie.setMaxAge(60*60*24*365); // 1 year
response.addCookie(userCookie);
%>

Code in .NET :-

<% System.Web.HttpCookie userCookie = new System.Web.HttpCookie("user","uid123");
System.DateTime dateTime = System.DateTime.Now;
System.TimeSpan timeSpan = new System.TimeSpan(0, 0, 60*60*24*365); // 1 year
cookie.Expires = dateTime.Add(timeSpan);
Response.Cookies.Add(userCookie);
%>

d) Beans :-

Java code :-

public class bean1 {
private String text = "Hello";
public bean1 (){
}

public String getText() {
return this.text;
}

public String setText(String text) {
this.text = text;
}
}

C# Code :-

using System;
public class bean1
{
virtual public System.String Text
{
get
{
return this.text;
}
set
{
this.text = value;
}
}
private System.String text = "Hello";
public bean1()
{
}
}

e) converting Servlets to ASP .NET code behind :-

Servlet sample code :-

import javax.servlet.*;
import javax.servlet.http.*;
public class SimpleServlet extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException,
java.io.IOException {
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter();
out.println("<html><body>");
out.println("Simple Servlet Body");
out.println("</body></html>");
out.close();
}
}

ASP .NET Code Behind sample :-

using System;
using System.Web;
using System.Web.UI;
public class SimpleServlet : System.Web.UI.Page
{
private void Page_Load(object sender,
System.EventArgs
{
Response.ContentType="text/html";
Response.Write("<html><body>");
Response.Write("Simple Servlet Body");
Response.Write("</body></html>");
}
}

f) Tag Library :-

JSP	ASP .NET
Tag Handler Class	ASP.NET Web User Controls
JSP Tag Library Descriptor	ASP.NET Web Custom Control
JSP taglib	Directive

JSP tag lib Sample code :-

<!- JSP -->
<!- the source file is specified in the TLD-->
<%@ taglib uri="taglib.tld" prefix="tags" %>
<tags:sample />

ASP .NET tag lib Sample code :-

<!- ASP .Net -->
<%@ Register TagPrefix="tags" TagName="sample" src="ExampleTag.ascx" %>
<tags:Sample id="mySample" runat="server"> </tags:Sample>

g) Converting Java Applets to .NET Winforms control

Applet code :-

package HelloWorldPackage;
public class HelloWorld extends Applet
{
public void paint(Graphics g) {
g.drawString(getParameter("parameter1"), 25, 25);
}
public void init() {}
public void start() {}
public void stop() {}
}

.NET Winforms code :-

namespace HelloWorldPackage
{
public class HelloWorld :System.Windows.Forms.UserControl
{
String parameter1;
bool isActive;
public HelloWorld()
{
init();
}
protected override void OnPaint(PaintEventArgs e)
{
e.Graphics.DrawString(parameter1,Font, new SolidBrush(ForeColor),25,25);
}
public void init()
{
this.GotFocus += new System.EventHandler(this.helloWorldControl1_Start);
this.LostFocus += new System.EventHandler(this.helloWorldControl1_Stop);
}
}

2. Business tier migration

Migrating EJB to .NET Serviced Component

a) EJB code :- (Session bean)

public class TellerBean implements SessionBean {
public void ejbCreate() {}
public void ejbRemove() throws
RemoteException {}
public void ejbActivate() throws RemoteException {}
public void ejbPassivate() throws RemoteException {}
public String getData()
}

.NET code :- (serviced component corresponding to the java session bean)

[Transaction(TransactionOption.Required)]
public class TellerBean : System.EnterpriseServices.ServicedComponent
{
public void Create() {}
virtual public System.String Data
{ get{...} }
protected override void Activate(){}
protected override void Deactivate(){ }
protected void Remove
{
this.Deactivate();
this.Dispose();
}
}

b) EJB Code :- (Entity Bean)

public class AccountEntity implements EntityBean {
private string accountID;
private int balance;
public get_accountID() { ... };
public get_balance() { ... };
public set_balance(int amount) { ... };
}
public class AccountProcess implements EntityBean {
public AccountEntity[] Inquiry() { ... };
public void Insert(AccountEntity account) {
string strQuery = "SELECT * FROM tb_account";
...
};
public void Update(AccountEntity account) { ... };
public void Delete(string accountID) { ... };
}

.NET Code :- (serviced component corresponding to the java entity bean)

[Transaction(TransactionOption.Required)]

public struct AccountEntity
{
private string accountID;
private int balance;
public AccountID { get{...}; }
public Balance { get{...}; set {...}; }
}
// dsAccount.xsd
public class dsAccount : System.Data.DataSet
{
...
}
public class AccountProcess : System.EnterpriseServices.ServicedComponent
{
public dsAccount Inquiry() { ... };
public void Insert(AccountEntity account)
{
DBAgent.ExecuteNonQuery("sp_getAccount", paramArray, ...);
...
};
public void Insert(string accountID, int balance, ... ){ ... }; // Alternative
}
Create Procedure sp_getAccount ( @accountID char(8), @balance int , ... )

c) Business Client Tier

Java Code :-

<%
try{
Context ctx = new InitialContext();
Object ref = ctx.lookup("TellerHome");
tellerHome = (TellerHome)
PortableRemoteObject.narrow(ref,
TellerHome.class);
teller = tellerHome.create();
out.println(teller.getData());
}
catch(Exception ex) {
out.println(ex.getMessage());
}
%>

.NET Code :-

<%
myPackage.TellerBean teller = new myPackage.TellerBean();
Response.Write(teller.Data);
%>

3) Data tier migration :-

a) Database connection :-

Java :- (JDBC)

Class.forName("com.ms.jdbc.odbc.JdbcOdbcDriver");
dbUrl = "jdbc:odbc:ADOTEST";
conn = DriverManager.getConnection(dbUrl,"sa","");

.NET (ADO .NET)

dbUrl = "Provider=SQLOLEDB;Data Source=dbserver;Initial Catalog=Master;"
System.Data.OleDb.OleDbConnection temp_Connection;
temp_Connection = new System.Data.OleDb.OleDbConnection(dbUrl);
temp_Connection.Open();
conn = temp_Connection;

b) Statement object :-

Java :- (JDBC)

Statement s = conn.createStatement();
createTableBooks = "SELECT count(au_lname) as nrows FROM authors";
ResultSet rs = s.executeQuery(createTableBooks);

.NET (ADO .NET)

System.Data.OleDb.OleDbCommand s = SupportClass.TransactionManager.manager.CreateStatement(conn);
createTableBooks = "SELECT count(au_lname) as nrows FROM authors";
ls.CommandText = createTableBooks;
System.Data.OleDb.OleDbDataReader rs = s.ExecuteReader();

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