Step By Step

Create Simple Calculator

Using Eclipse Galileo & EJB 3.0

Created by :

SAIDY Fouad

http://fouad-saidy.blogspot.com

fouadsaidy@gmail.com

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

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

This is a simple tutorial to show you by examples how to create your first EJB Application in Eclipse Galileo using EJB 3.0.

We will use in this tutorial:

Eclipse Galileo IDE (download http://www.eclipse.org/downloads/download.php?file=/technology/epp/downloads/release/galileo/SR1/

eclipse-jee-galileo-SR1-win32.zip )

JBoss-5.1.0.GA ( download http://sourceforge.net/projects/jboss/files/JBoss/JBoss-5.1.0.GA/ )

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

1. Configuration JBoss Server:

Configuration JBoss Server:

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

In Eclipse Menu choose Window--> Preferences, and 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! : 

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You added the Jboss Server to Eclipse; now let's add the Jboss Server to this section: 

Select the Server section click and choose new->Server then 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

Check JDK if is not checked, or add it if it doesn't exist: 

We just finished configuration step let's move now to programming an EJB Application. 

2. 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: 

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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 ejb:

 

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, don’t forget 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) 

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{ 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. 

2. Web Client Application:

Select File-->New-->Dynamic Web Project, its name: SimpleCalculatorWeb 

Add a JSP page called index to the WebContent directory: 

 

Add this form to index.jsp: 

<h2> <b> Hello World To The Simple Calculator </b> </h2> 

<%

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());

%>

<form method="post" action="calcServlet">

 <b>Number 1:</b><input type='text' name='n1' value="<%=a%>" /> <br/> 

<b>Number 2:</b><input type='text' name='n2' value="<%=b%>" /> <br/> 

<u><b>Options:</b></u> <br/>

<ul>  

<li><b>+</b><input type='radio' name="oper" value='+' checked /></li>  

<li><b>&nbsp;-</b><input type='radio' name="oper" value='-' /></li>

<li><b>*</b><input type='radio' name="oper" value='*' /></li> 

<li>&nbsp; <b>/</b><input type='radio' name="oper" value='/' /></li> </ul> 

<b>-------------------------------------------</b> <br/> 

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<input type="submit" value="Executer" /> </form>

<font color='blue'><b>Result is: </b> <%=session.getAttribute("result")%> </font> <br/>

<font color='red' >Error: <%=session.getAttribute("error")%></font>

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

Servlet is created like this: 

 

Add those imports 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; 

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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 web client application to reference 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 projects, firstly play the JBoss Server in Server section:

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Deploying the EJB Project:

With the same way deploy SimpleCalculatorWeb:

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Congratulation this is your first simple Calculator using EJB 3.0 ^^.

If you have any remarks or questions don’t hesitate to alert me by email: fouadsaidy@gmail.com.