Jetty supports interpretation and application of the following annotations:

Some types of annotation can be placed on any class, not necessarily just those with which the container interacts directly. These type of annotations are refered to as "discovered" to indicate that the container must take proactive action to go out and find them. The other type of annotation is call "introspected", meaning that they occur on classes with which the container interacts during their lifecycle (e.g. javax.servlet.Servlet, javax.servlet.Filter, …​etc.), and hence can be found by simple inspection of the class at that point.

Some examples of discovered annotations are:

Some examples of introspected annotations are:

The web.xml file can contain the attribute metadata-complete. If this is set to true, then no scanning of discoverable annotations takes place. However, scanning of classes may still occur because of javax.servlet.ServletContainerInitializers. Classes implementing this interface are found by Jetty using the javax.util.ServiceLoader mechanism, and if one is present and it includes the @HandlesTypes annotation, then Jetty must scan the class hierarchy of the web application. This may be very time-consuming if you have many jars in the container’s path or in the webapp’s WEB-INF/lib.

If scanning is to take place - because either metadata-complete is false or missing, or because there are one or more javax.servlet.ServletContainerIntializers with @HandlesTypes - then Jetty must consider both the container’s classpath and the webapp’s classpath.

By default, Jetty will not scan any classes that are on the container’s classpath. If you need to cause jars and classes that are on the container’s classpath to be scanned, then you can use the org.eclipse.jetty.server.webapp.ContainerIncludeJarPattern context attribute to specify a pattern for jars and directories from the container’s classpath to scan.

By default Jetty will scan allclasses from WEB-INF/classes and all jars from WEB-INF/lib according to the order, if any, established by absolute or relative ordering clauses in web.xml. If your webapp contains many jar files, you can significantly speed up deployment by omitting them from scanning. To do this, use the org.eclipse.jetty.server.webapp.WebInfIncludeJarPattern context attribute to define the patterns of jars that you specifically want to be scanned.

Note that if you have configured an extraClasspath for the webapp, then it participates in the scanning process too. Any classes dirs are treated the same for scanning purposes as if they were in WEB-INF/classes and jars are treated as if they were in WEB-INF/lib.

See also the next section on ServletContainerInitializers if you need to control the order in which they are applied.

If annotation scanning is to be performed, by default Jetty will do it in a multi-threaded manner in order to complete it in the minimum amount of time.

If for some reason you don’t want multi-threaded scanning, you can configure Jetty to revert to single-threaded scanning. There are several ways to configure this:

Method 1 will only affect the current webapp. Method 2 will affect all webapps deployed to the same Server instance. Method 3 will affect all webapps deployed in the same JVM.

By default, Jetty will wait a maximum of 60 seconds for all of the scanning threads to complete. You can set this to a higher or lower number of seconds by doing one of the following:

Method 1 will only affect the current webapp. Method 2 will affect all webapps deployed to the same Server instance. Method 3 will affect all webapps deployed in the same JVM.

The javax.servlet.ServletContainerInitializer class can exist in: the container’s classpath, the webapp’s WEB-INF/classes directory, the webapp’s WEB-INF/lib jars, or any external extraClasspath that you have configured on the webapp.

The Servlet Specification does not define any order in which a ServletContainerInitializer must be called when the webapp starts. By default Jetty will call them in the following order:

As is the case with annotation scanning, the extraClasspath is fully considered for ServletContainerInitializer callbacks. ServletContainerInitializer derived from a classes directory on the extraClasspath and jars from an extraClasspath for the webapp are called in step 2 and 3, respectively.

WebAppContext context = new WebAppContext();
context.setAttribute("org.eclipse.jetty.containerInitializerOrder",
                     "org.eclipse.jetty.websocket.jsr356.server.deploy.WebSocketServerContainerInitializer, com.acme.Foo.MySCI, *");

WebAppContext context = new WebAppContext();
context.setAttribute("org.eclipse.jetty.containerInitializerExclusionPattern",
                     "com.acme.*|com.corp.SlowContainerInitializer");