Configure embedded jetty with web.xml?

Question

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 1

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:

• WebAppContext.setClassLoader(ClassLoader classloader)
• WebAppContext.addServerClass(String classOrPackage)
• WebAppContext.addSystemClass(String classOrPackage)