Configure embedded jetty with web.xml?
I am trying to generate both a war with my web application as well as a self contained jar file with embedded jetty. For the embedded jetty (the jar file distribution) I add a servlet as follows:
public static void main(String[] args) throws Exception {
Server server = new Server(8080);
ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
context.setContextPath("/");
server.setHandler(context);
context.addServlet(new ServletHolder(new HelloServlet()),"/*");
server.start();
server.join();
}
The war file distribution uses a web.xml file that contains the following in the web-app section:
<servlet>
<servlet-class>com.example.HelloServlet</servlet-class>
<servlet-name>SimplestServer</servlet-name>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
This works. However, I want to get rid of the duplication between the two approaches. I.e., when I add a new servlet I want to have to configure it in only one location. Can I load and use the web.xml file from the embedded jetty?
Answer
Use a org.eclipse.jetty.webapp.WebAppContext
Example:
package jetty;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.webapp.WebAppContext;
public class OnWebApp
{
public static void main(String[] args) throws Exception
{
// Create a basic jetty server object that will listen on port 8080.
// Note that if you set this to port 0 then a randomly available port
// will be assigned that you can either look in the logs for the port,
// or programmatically obtain it for use in test cases.
Server server = new Server(8080);
// The WebAppContext is the entity that controls the environment in
// which a web application lives and breathes. In this example the
// context path is being set to "/" so it is suitable for serving
// root context requests and then we see it setting the location of
// the war. A whole host of other configurations are available,
// ranging from configuring to support annotation scanning in the
// webapp (through PlusConfiguration) to choosing where the webapp
// will unpack itself.
WebAppContext webapp = new WebAppContext();
webapp.setContextPath("/");
webapp.setWar("path/to/my/test.war");
// A WebAppContext is a ContextHandler as well so it needs to be set to
// the server so it is aware of where to send the appropriate requests.
server.setHandler(webapp);
// Start things up! By using the server.join() the server thread will
// join with the current thread.
// See http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/Thread.html#join()
// for more details.
server.start();
server.join();
}
}
Note that you will build a normal WAR file, and use it with Jetty.
If you have special requirements such as Annotation scanning or JNDI, then you'll need to get into configuration specification.
// Enable parsing of jndi-related parts of web.xml and jetty-env.xml
org.eclipse.jetty.webapp.Configuration.ClassList classlist =
org.eclipse.jetty.webapp.Configuration.ClassList.setServerDefault(server);
// Enable JNDI
classlist.addAfter("org.eclipse.jetty.webapp.FragmentConfiguration",
"org.eclipse.jetty.plus.webapp.EnvConfiguration",
"org.eclipse.jetty.plus.webapp.PlusConfiguration");
// Enable Annotation Scanning
classlist.addBefore("org.eclipse.jetty.webapp.JettyWebXmlConfiguration",
"org.eclipse.jetty.annotations.AnnotationConfiguration");
For a longer example of this in a WebAppContext, see the ServerWithAnnotations example.
Also note that you will have all of the webapp classloader rules in place using this technique as well. Meaning you will have a classloader for the webapp and another one for the server. This is important to understand.
There are a few tweaks you can do to the WebAppContext for classloaders, but you can't eliminate them, just control how they behave.
WebAppContext webapp = new WebAppContext();
// ... various setup of the webapp ...
// Flip the classloader priority from servlet spec where webapp is first to
// Standard java behavior of parent (aka Server classloader) is first.
webapp.setParentLoaderPriority(true);
See also: