Migration from J2EE to .NET

Migration from J2EE to .NET
by vivek devarajan.


Hi all, 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 :--

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

Highlights of the migration strategy

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

i. Presentation tier migration

  1. JSP -> ASP .NET (sample code snippets)

    JSP scriptlet :--
    <!--Scriptlet--> 

<%
      for(int i = 0; i < 3; i++) {
            out.println(i + "<br>"); 
      }
%>
    ASP .NET scriptlet :--
    <!--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 :--
    <script runat="server" language="c#">
      public virtual string foo() 
      {
            return "foo";
      } 
</script>
  2. Implicit objects :--

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

  3. 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); 
%>
  4. 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{

      private string text = "Hello";
      
      public Bean1() {} 

      public string Text
      {
            get { return text; }
            set { text = value; }
      }
}
  5. Converting Servlets to ASP .NET code behind :--

    Servlet sample code :--
    import javax.servlet.*; 
import javax.servlet.http.*;

import java.io.*;

public class SimpleServlet extends HttpServlet {

      public void doGet(HttpServletRequest request, 
                  HttpServletResponse response)
                  throws ServletException, java.io.IOException {
            
            response.setContentType("text/html");
            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, EventArgs args)
      {
            Response.ContentType = "text/html";
            
            Response.Write("<html><body>");
            Response.Write("Simple Servlet Body");
            Response.Write("</body></html>");
      }
}
  6. Tag Library :--

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

    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" />
  7. 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 EventHandler(this.helloWorldControl1_Start);
            this.LostFocus +=
                  new EventHandler(this.helloWorldControl1_Stop);
      }
}

ii. Business tier migration

  1. Migrating EJB to .NET Serviced Component

    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() {
            return "some data";
      }
}
    .NET code :-- (serviced component corresponding to the java session bean)
    [Transaction(TransactionOption.Required)] 
public class TellerBean : System.EnterpriseServices.ServicedComponent
{
      public virtual string Data
      {
            get { return "some data"; }
      }

      public void Create() {}
      protected override void Activate() {}
      protected override void Deactivate() {} 
      
      protected void Remove {
            Deactivate();
            Dispose();
      }
}
    EJB Code :-- (Entity Bean)
    public class AccountEntity implements EntityBean { 

  private string accountID;
  private int balance;

  public getAccountID() { ?}

  public getBalance() { ?}
  public setBalance(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 PRODECURE sp_getAccount
      @accountID char(8),
      @balance int,
      ?
AS
      ..
  2. 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);
%>

iii. Data tier migration

  1. 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;";

using(OleDbConnection conn = new OleDbConnection(dbUrl))
{
      conn.Open();
      ...
}
  2. 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)
    string cmdText = "SELECT count(au_lname) as nrows FROM authors";

using(OleDbCommand cmd = new OleDbCommand(cmdText, conn))
{
      OleDbDataReader rs = cmd.ExecuteReader();
      ...
}

posted on 2004-11-23 14:11  小牛哥  阅读(1688)  评论(0)  编辑  收藏  举报

导航