Embedded Servlet Containers

Hammock provides support for three embedded servlet runtimes. Each webserver is started during the CDI event AfterDeploymentValidation, and is registered as a CDI extension.

Apache Tomcat

Apache Tomcat is based on the 9.0 series of milestones, providing early previews of Servlet 4 functionality. It also helps fix a concurrency issue with Weld caused by start/stops occurring on different threads. To use it in your project, add a dependency on ws.ament.hammock:web-tomcat. It does support WebSockets as well as Servlets, Filters and Listeners. Listeners are not treated as CDI beans.

JBoss Undertow

JBoss Undertow is a light weight embedded container runtime. To use it in your project, add a dependency on ws.ament.hammock:web-tomcat. To use WebSockets, you need to have an annotated endpoint. It supports Servlets, Filters and Listeners via normal means.

Eclipse Jetty

Using the module ws.ament.hammock:web-jetty brings in Jetty as your webserver. It supports WebSockets, Servlets, Filters and Listeners. The Decorator used, intended to inject into fields, replaces the instance with an unmanaged version from CDI.

Configuration settings

The below configuration settings can be added to any property file or other ConfigSource you register.

Property Name Default Value Description



The HTTP Listen Port


The Bind Address, the default means it will listen on all addresses



The location to load static files from



If non-zero, starts an HTTPS listener on the given port



The keystore path. Must be set for SSL support.



The keystore type. Must be set for SSL support.



The keystore password. Must be set for SSL support.



The location for the truststore. This property is not used in Tomcat



The truststore type. This property is not used in Tomcat



The truststore password. This property is not used in Tomcat

Understanding Container Behavior

Hammock creates instances of unmanaged beans to better align to how the Java EE specification treats these resources. However, there is a relationship with CDI Bean Discovery:

  • bean-discovery-mode=none means that no components will be discovered within that specific JAR file

  • bean-discovery-mode=all means that all components will be scanned. You can optionally use a <trim/> tag.

  • bean-discovery-mode=annotated means that the only components to be scanned are those with bean defining annotations. Functionally, this means you should add @Dependent as your scope for these classes.

Which means in bean-discovery-mode=all the following servlet would be discovered:

@WebServlet(urlPatterns = {"/*"}, name = "DefaultServlet")
public class DefaultServlet extends HttpServlet{

But would not be discovered in bean-discovery-mode=annotated or with <trim/> enabled. To discovery it in these, you must change its definition to:

@WebServlet(urlPatterns = {"/*"}, name = "DefaultServlet")
public class DefaultServlet extends HttpServlet{

Note the explicit usage of @Dependent versus the implicit usage in the first definition.

Using Annotations

@WebFilter, @WebServlet, and @WebListener are the preferred means to registering your component. URL mappings can be represented as configuration properties, which can even be a comma separated list. Take for example how the Camel Servlet is registered:

@WebServlet(urlPatterns = {"${camel.servlet.uri}"}, name = "CamelServlet")
public class HammockCamelServlet extends CamelHttpTransportServlet {

This configuration property will be resolved at deployment time only and set the path. There is a default value that is used when this property is not available.