Web applications and web services - OSGi in Action - page 482

Configuring the HTTP Service
The HTTP Service is registered by an implementation bundle. The client has no con-
trol over the port or URL on which the service is running. That's the job of the admin-
istrator of the OSGi framework. The HTTP Service specification defines framework
properties to configure the service ports:
■ org.osgi.service.http.port —Specifies the port used for servlets and
resources accessible via HTTP. The default value is 80.
■ org.osgi.service.http.port.secure —Specifies the port used for servlets
and resources accessible via HTTPS. The default value is 443.
You can set framework properties using the launching API covered in chapter 13. In
this case, the launcher passes system properties through to the framework proper-
ties. It's also generally possible to configure the HTTP Service implementation using
the Configuration Admin Service, but that is implementation-dependent.
SETTING THE HTTPCONTEXT
You may have noticed the HttpContext parameter in the HttpService.register-
Resources() method. In the previous example, you passed in null , but what does this
parameter do? HttpContext provides a way to inject the HTTP Service with resource-
lookup and -access policies. Let's first look at the API , followed by an example, to show
what this allows you to do. The HttpContext interface is defined as follows:
public interface HttpContext {
boolean handleSecurity(HttpServletRequest req, HttpServletResponse res)
throws IOException;
URL getResource(String name);
String getMimeType(String path);
}
The handleSecurity() method provides a callback to allow the HTTP Service to verify
whether a request should be allowed for a given resource. The getResource()
method provides a mechanism to define how a particular resource is mapped to a
URL , which makes it possible to host contents from any scheme accessible from URL s.
Finally, the getMimeType() provides a mechanism to control the MIME type headers
returned with the stream of a particular resource.
If you use null for the HttpContext , as in the previous example, the HTTP Service
uses a default context implementation, which can also be accessed using the Http-
Service.createDefaultHttpContext() method. Table 15.1 describes the behavior of
the default HttpContext as defined by the OSG i specification.
To demonstrate how to use the HttpContext , let's create a ResourceTracker to
track bundles and automatically register their resources with the HTTP Service. To
accomplish this, you'll use the org.osgi.util.tracker.BundleTracker introduced
in the OSG i R4.2 Compendium specification. Listing 15.2 shows the body of the add-
Bundle() method of the BundleTracker subclass.