6.5.1.1 To Add a Context Parameter Using NetBeans IDE

These steps apply generally to web applications but do not apply specifically to the examples in this chapter.

1. Open the project.

2. Expand the project's node in the Projects tree.

3. Expand the Web Pages node and then the WEB-INF node.

4. Double-click web.xml.

   If the project does not have a web.xml file, create one by following the steps in To Create a web.xml File Using NetBeans IDE.

5. Click General at the top of the editor window.

6. Expand the Context Parameters node.

7. Click Add.

8. In the Add Context Parameter dialog box, in the Parameter Name field, enter the name that specifies the context object.

9. In the Parameter Value field, enter the parameter to pass to the context object.

10. Click OK.

6.5.1.2 To Create a web.xml File Using NetBeans IDE

1. From the File menu, choose New File.

2. In the New File wizard, select the Web category, then select Standard Deployment Descriptor under File Types.

3. Click Next.

4. Click Finish.

   A basic web.xml file appears in web/WEB-INF/.

6.5.3.1 To Set Up Error Mapping Using NetBeans IDE

These steps apply generally to web applications but do not apply specifically to the examples in this chapter.

1. Open the project.

2. Expand the project's node in the Projects tab.

3. Expand the Web Pages node and then the WEB-INF node.

4. Double-click web.xml.

   If the project does not have a web.xml file, create one by following the steps in To Create a web.xml File Using NetBeans IDE.

5. Click Pages at the top of the editor window.

6. Expand the Error Pages node.

7. Click Add.

8. In the Add Error Page dialog box, click Browse to locate the page that you want to act as the error page.

9. Specify either an error code or an exception type.

   • To specify an error code, in the Error Code field enter the HTTP status code that will cause the error page to be opened, or leave the field blank to include all error codes.

   • To specify an exception type, in the Exception Type field enter the exception that will cause the error page to load. To specify all throwable errors and exceptions, enter java.lang.Throwable.

10. Click OK.

6.5.4.1 Declaring a Reference to a Resource

The @Resource annotation is used to declare a reference to a resource, such as a data source, an enterprise bean, or an environment entry.

The @Resource annotation is specified on a class, a method, or a field. The container is responsible for injecting references to resources declared by the @Resource annotation and mapping it to the proper JNDI resources.

In the following example, the @Resource annotation is used to inject a data source into a component that needs to make a connection to the data source, as is done when using JDBC technology to access a relational database:

@Resource javax.sql.DataSource catalogDS;
public getProductsByCategory() {
    // get a connection and execute the query
    Connection conn = catalogDS.getConnection();
    ...
}

The container injects this data source prior to the component's being made available to the application. The data source JNDI mapping is inferred from the field name, catalogDS, and the type, javax.sql.DataSource.

If you have multiple resources that you need to inject into one component, you need to use the @Resources annotation to contain them, as shown by the following example:

@Resources ({
    @Resource(name="myDB" type=javax.sql.DataSource.class),
    @Resource(name="myMQ" type=javax.jms.ConnectionFactory.class)
})

The web application examples in this tutorial use the Java Persistence API to access relational databases. This API does not require you to explicitly create a connection to a data source. Therefore, the examples do not use the @Resource annotation to inject a data source. However, this API supports the @PersistenceUnit and @PersistenceContext annotations for injecting EntityManagerFactory and EntityManager instances, respectively. Chapter 38, "Running the Persistence Examples" describes these annotations and the use of the Java Persistence API in web applications.

6.5.4.2 Declaring a Reference to a Web Service

The @WebServiceRef annotation provides a reference to a web service. The following example shows uses the @WebServiceRef annotation to declare a reference to a web service. WebServiceRef uses the wsdlLocation element to specify the URI of the deployed service's WSDL file:

...
import javax.xml.ws.WebServiceRef;
...
public class ResponseServlet extends HTTPServlet {
@WebServiceRef(wsdlLocation="http://localhost:8080/helloservice/hello?wsdl")
static HelloService service;