Creating the Enterprise Bean
Java Platform, Enterprise Edition (Java EE) 8
The Java EE Tutorial

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Creating the Enterprise Bean

The enterprise bean in our example is a stateless session bean called ConverterBean. The source code for ConverterBean is in the _tut-install_/examples/ejb/converter/src/main/java/ directory.

Creating ConverterBean requires these steps:

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

  2. 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 javaeetutorial.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 under the _tut-install_/examples/ejb/converter/src/main/java/ directory:

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.EJB annotation is added to the declaration of the private member variable converter, which is of type ConverterBean. ConverterBean exposes a local, no-interface view, so the enterprise bean implementation class is the variable type:

@WebServlet(urlPatterns="/")
public class ConverterServlet extends HttpServlet {
  @EJB
  ConverterBean converter;
  ...
}

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 Maven to build, package, deploy, and run the converter example.

The following topics are addressed here:

To Run the converter Example Using NetBeans IDE

  1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).

  2. From the File menu, choose Open Project.

  3. In the Open Project dialog box, navigate to:

    tut-install/examples/ejb
  4. Select the converter folder.

  5. Click Open Project.

  6. In the Projects tab, right-click the converter project and select Build.

  7. Open a web browser to the following URL:

    http://localhost:8080/converter
  8. On the Servlet ConverterServlet page, enter 100 in the field and click Submit.

    A second page opens, showing the converted values.

To Run the converter Example Using Maven

  1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).

  2. In a terminal window, go to:

    tut-install/examples/ejb/converter/
  3. Enter the following command:

    mvn install

    This command compiles the source files for the enterprise bean and the servlet, packages the project into a WAR module (converter.war), and deploys the WAR to the server. For more information about Maven, see Building the Examples.

  4. Open a web browser to the following URL:

    http://localhost:8080/converter
  5. On the Servlet ConverterServlet page, enter 100 in the field and click Submit.

    A second page opens, showing the converted values.


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