Creating the Enterprise Bean - The Java EE 6 Tutorial (original) (raw)

The enterprise bean in our example is a stateless session bean calledConverterBean. The source code for ConverterBean is in the tut-install/examples/ejb/converter/src/java/ directory.

Creating ConverterBean requires these steps:

Coding the bean’s implementation class (the source code is provided)
Compiling the source code

Coding the Enterprise Bean Class

The enterprise bean class for this example is called ConverterBean. This class implements two business methods: dollarToYen and yenToEuro. Because the enterprise bean class doesn’t implement a business interface, the enterprise bean exposes a local, no-interface view. The public methods in the enterprise bean class are available to clients that obtain a reference to ConverterBean. The source code for the ConverterBean class is as follows:

package converter.ejb;

import java.math.BigDecimal; import javax.ejb.*;

@Stateless public class ConverterBean { private BigDecimal yenRate = new BigDecimal("83.0602"); private BigDecimal euroRate = new BigDecimal("0.0093016");

public BigDecimal dollarToYen(BigDecimal dollars) {
    BigDecimal result = dollars.multiply(yenRate);
    return result.setScale(2, BigDecimal.ROUND_UP);
}

public BigDecimal yenToEuro(BigDecimal yen) {
    BigDecimal result = yen.multiply(euroRate);
    return result.setScale(2, BigDecimal.ROUND_UP);
}

}

Note the @Stateless annotation decorating the enterprise bean class. This annotation lets the container know that ConverterBean is a stateless session bean.

Creating the converter Web Client

The web client is contained in the following servlet class:

tut-install/examples/ejb/converter/src/java/converter/web/ConverterServlet.java

A Java servlet is a web component that responds to HTTP requests.

The ConverterServlet class uses dependency injection to obtain a reference to ConverterBean. The javax.ejb.EJBannotation is added to the declaration of the private member variable converterBean, which is of type ConverterBean. ConverterBean exposes a local, no-interface view, so the enterprise bean implementation class is the variable type:

@WebServlet public class ConverterServlet extends HttpServlet { @EJB ConverterBean converterBean; ... }

When the user enters an amount to be converted to yen and euro, the amount is retrieved from the request parameters; then the ConverterBean.dollarToYen and the ConverterBean.yenToEuro methods are called:

... try { String amount = request.getParameter("amount"); if (amount != null && amount.length() > 0) { // convert the amount to a BigDecimal from the request parameter BigDecimal d = new BigDecimal(amount); // call the ConverterBean.dollarToYen() method to get the amount // in Yen BigDecimal yenAmount = converter.dollarToYen(d);

// call the ConverterBean.yenToEuro() method to get the amount
// in Euros
BigDecimal euroAmount = converter.yenToEuro(yenAmount);
...

} ... }

The results are displayed to the user.

Running the converter Example

Now you are ready to compile the enterprise bean class (ConverterBean.java) and the servlet class (ConverterServlet.java) and to package the compiled classes into a WAR file. You can use either NetBeans IDE or Ant to build, package, deploy, and run the converter example.

To Build, Package, and Deploy the converter Example in NetBeans IDE

From the File menu, choose Open Project.
In the Open Project dialog, navigate to:
tut-install/examples/ejb/
Select the converter folder.
Select the Open as Main Project check box.
Click Open Project.
In the Projects tab, right-click the converter project and select Deploy.

To Build, Package, and Deploy the converter Example Using Ant

In a terminal window, go to:
tut-install/examples/ejb/converter/
Type the following command:
ant all
This command calls the default task, which compiles the source files for the enterprise bean and the servlet, placing the class files in the build subdirectory (not the src directory) of the project. The default task packages the project into a WAR module: converter.war. For more information about the Ant tool, see Building the Examples.

Note - When compiling the code, the ant task includes the Java EE API JAR files in the classpath. These JARs reside in the modules directory of your GlassFish Server installation. If you plan to use other tools to compile the source code for Java EE components, make sure that the classpath includes the Java EE API JAR files.

To Run the converter Example

Open a web browser to the following URL:
http://localhost:8080/converter
The Servlet ConverterServlet page opens.
Type 100 in the input field and click Submit.
A second page opens, showing the converted values.