Step By Step Create Simple Calculator using Eclipse Galileo & EJB 3.0

admin — Sat, 30 Jan 2010 12:41:44 +0000

Remark:

I received many emails that talk about the error of “Firstcalc not bound” the problem that if you didn’t referenced the EJB project in the web application your server can not know the calcImpl class for this reason it shows this error.
To resolve this error just try to remove @Stateless(mappedName = “Firstcalc”) and replace it by @stateless,in the naming function in the servlet replace calc cl = (calc) ctx.lookup(”Firstcalc”); by cl=(calc) ctx.lookup(”calcImpl/local”);
I used the bounding without a mapped name of the calcImpl class, it’s Work correctly(tested with jboss server).

This tutorial is available in pdf book : Step By Step Create Simple Calculator using Eclipse Galileo & EJB 3.0

We will use in this tutorial:

we will create an application in the server side based on EJB 3.0, and an author web client application

Server Application Using EJB:

Configuration JBoss Server:

The second step is to configuarate the Jboss server in Eclipse Galieo IDE:

in Eclipse Menu choose Window–> Preferences, then choose
Server –> Runtime Environments.

click add Button then choose JBoss–> JBoss v5.0 and check” Create a new local server”

In Application Server Directory select the JBoss Server directory,
not the Content of the directory! :

you added the Jboss Server to Eclipse , now let’s add the Jboss Server
to this section:

select the Server section clik and choose new->Server then next next
until finish

the server appears like this in Server section:

Now we will verify that Jdk is the default installed JRE’s :

select Window–>Preferences in this windows select Java–> Installed JREs
then if jdk is not checked check it ,or add it if it doesn’t exist:

we finished configuration step let’s move now to programming an
EJB Application.

EJB Application:

in this application we will create :

Remote Interface calc,

Class calcImpl which implements calc.

select File–>New–> Other.. then create EJB Project :

specify the name of the project for example SimpleCalculator , and choose the JBoss v5 in target field:

now we created a simple ejb project ,we will create source code in ejbModule directory :

we finished creating EJB project, create the interface calc with package first :

add this code to your calc interface:

package ejb;

import javax.ejb.Local;

@Local

public interface calc {

public float sum(float a,float b);

public float mult(float a,float b);

public float minus(float a,float b);

public float div(float a,float b);

}

next step is to create calcImpl with the same way dont forgit to specify the same package (ejb), and add this code to class:

package ejb; import javax.ejb.Stateless;
@Stateless(mappedName=”Firstcalc”)

public class calcImpl implements calc {
public float sum(float a,float b)
{ return a+b; }
public float mult(float a,float b)
{ return a*b; }
public float minus(float a,float b)
{ return a-b; }
public float div(float a,float b) {
try {
return a/b;
}catch(Exception e){
System.out.println(”Error:devision by 0!!”);
return 0;
}
}
}

now we finished EJB Application let’s move to The Web Client Application.

Web Client Application:

select File–>New–>Dynamic Web Project , it’s name: SimpleCalculatorWeb

add a jsp page called index to the WebContent directory :

add this form to index.jsp:

Hello World To The Simple Calculator

<% float a=2,b=1;
if (request.getAttribute(”a”)!=null)
a=Float.parseFloat(request.getAttribute(”a”).toString());
if( request.getAttribute(”b”)!=null)
b=Float.parseFloat(request.getAttribute(”b”).toString()); %>

Result is: <%=session.getAttribute(”result”)%>

Error: <%=session.getAttribute(”error”)%>

now create a calServlet with web package in the JavaResources :src directory :

servlet is created like this:

add those import to your servlet class:

import java.io.IOException;
import javax.naming.*;
import javax.servlet.*;
import javax.servlet.*;
import javax.servlet.http.*;

copy this code to the doGet function :

HttpSession session=request.getSession(true);
RequestDispatcher rd=this.getServletContext().getRequestDispatcher(”/index.jsp”);

float a=Float.parseFloat(request.getParameter(”n1″));
float b=Float.parseFloat(request.getParameter(”n2″));
char oper=request.getParameter(”oper”).charAt(0);
float result=0;
try {
Context ctx=new InitialContext();
// call the calcImpl class of the SimpleCalculator EJB with the mappedName
calc cl=(calc) ctx.lookup(”Firstcalc”);
switch(oper)
{
case ‘+’: result=cl.sum(a, b); break;
case ‘-’: result =cl.minus(a, b); break;
case ‘*’: result =cl.mult(a, b); break;

case ‘/’: result =cl.div(a, b); break;
}
session.setAttribute(”result”,result); request.setAttribute(”a”, a); request.setAttribute(”b”, b);
}catch(NamingException e){
session.setAttribute(”erreur: “,e.getMessage());
}
rd.forward(request,response);

to let the the web client application to know the calc interface we must configure the build path of the project in adding the first project SimpleCalculator :

in the project section click add and select SimpleCalculator:

now add this import to your servlet class :
import ejb.calc;

let’s deploy the two project ,firstly play the JBoss Server in Server section:

deploying the EJB Project :

with the same way deploy SimpleCalculatorWeb:

if you have any remarks or questions dont hesitate to post it.

Fouad's Blog » JEE

Step By Step Create Simple Calculator using Eclipse Galileo & EJB 3.0

Remark:

Hello World To The Simple Calculator