Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## 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

- To Run the converter Example Using Maven

#### 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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