Overview

The Servlet module provides CDI integration with the Java Servlet API. It enables injection of common servlet objects and propagation of servlet events to the CDI event bus.

Project Setup

The configuration information provided here is for Maven-based projects and it assumes that you have already declared the DeltaSpike version and DeltaSpike Core module for your projects, as detailed in Configure DeltaSpike in Your Projects. For Maven-independent projects, see Configure DeltaSpike in Maven-independent Projects.

1. Declare Servlet Module Dependencies

Add the Servlet module to the list of dependencies in the project pom.xml file using this code snippet:

<dependency>
    <groupId>org.apache.deltaspike.modules</groupId>
    <artifactId>deltaspike-servlet-module-api</artifactId>
    <version>${deltaspike.version}</version>
    <scope>compile</scope>
</dependency>

<dependency>
    <groupId>org.apache.deltaspike.modules</groupId>
    <artifactId>deltaspike-servlet-module-impl</artifactId>
    <version>${deltaspike.version}</version>
    <scope>runtime</scope>
</dependency>

Or if you’re using Gradle, add these dependencies to your build.gradle:

     runtime 'org.apache.deltaspike.modules:deltaspike-servlet-module-impl'
     compile 'org.apache.deltaspike.modules:deltaspike-servlet-module-api'

2. Configure Listeners and Filters

In most cases there is no need for any additional configuration beside adding the required dependencies to your project, because all required listeners and filters are automatically registered in the container.

However there are certain situations in which you will have to manually register the listeners and filters in your web.xml:

Your container does not support Servlet 3.0 or newer.
You have set metadata-complete=true in your web.xml.
You packaged the servlet module in the lib directory of an EAR archive.

In these cases you will have to add the following section manually to the project web.xml:

<listener>
    <display-name>EventBridgeContextListener</display-name>
    <listener-class>org.apache.deltaspike.servlet.impl.event.EventBridgeContextListener</listener-class>
</listener>

<listener>
    <display-name>EventBridgeSessionListener</display-name>
    <listener-class>org.apache.deltaspike.servlet.impl.event.EventBridgeSessionListener</listener-class>
</listener>

<listener>
    <display-name>ServletContextHolderListener</display-name>
    <listener-class>org.apache.deltaspike.servlet.impl.produce.ServletContextHolderListener</listener-class>
</listener>

<listener>
    <display-name>RequestResponseHolderListener</display-name>
    <listener-class>org.apache.deltaspike.servlet.impl.produce.RequestResponseHolderListener</listener-class>
</listener>

<filter>
    <display-name>RequestResponseHolderFilter</display-name>
    <filter-name>RequestResponseHolderFilter</filter-name>
    <filter-class>org.apache.deltaspike.servlet.impl.produce.RequestResponseHolderFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>RequestResponseHolderFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<filter>
    <display-name>EventBridgeFilter</display-name>
    <filter-name>EventBridgeFilter</filter-name>
    <filter-class>org.apache.deltaspike.servlet.impl.event.EventBridgeFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>EventBridgeFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

Injectable Servlet Objects

The DeltaSpike Servlet module contains producers for many objects of a Servlet environment. All produces are using the special qualifier @DeltaSpike for compatibility with CDI 1.1, which supports the injection of some Servlet objects out of the box.

The following code shows the general injection pattern to use for all objects.

@Inject @DeltaSpike
private ServletObject servletObject;

ServletContext

The ServletContext is made available in the application scope. It can be injected into any CDI bean like this:

@Inject @DeltaSpike
private ServletContext servletContext;

ServletRequest / HttpServletRequest

The ServletRequest is made available in the request scope. The current request can be injected into a CDI bean like this:

@Inject @DeltaSpike
private ServletRequest request;

In case of HTTP requests you can also inject the HttpServletRequest:

@Inject @DeltaSpike
private HttpServletRequest request;

ServletResponse / HttpServletResponse

The ServletResponse is made available in the request scope. The current response can be injected into a CDI bean like this:

@Inject @DeltaSpike
private ServletResponse response;

In case of HTTP requests you can also inject the HttpServletResponse:

@Inject @DeltaSpike
private HttpServletResponse response;

HttpSession

The HttpSession is made available in the session scope. You can inject the current session of a user into a CDI bean like this:

@Inject @DeltaSpike
private HttpSession session;

Please note that injecting the session this way will force the creation of a session.

Principal

The Principal is made available in the request scope. The current principal can be injected into a CDI bean like this:

@Inject @DeltaSpike
private Principal principal;

The Principal is obtained by calling getUserPrincipal() on the HttpServletRequest.

Servlet Event Propagation

The DeltaSpike Servlet module propagates a number of Servlet object lifecycle events to the CDI event bus. This allows regular CDI beans to observe these events and react accordingly.

In most cases the event type is the object whose lifecycle is observed. To distinguish between construction and destruction of the corresponding object, DeltaSpike uses the qualifiers @Initialized and @Destroyed.

The following sections shows which concrete Servlet objects are supported and how their lifecycle can be observed.

Servlet Context Lifecycle Events

The Servlet module supports initialization and destruction events for the ServletContext. These events can for example be used to detect application startup or shutdown. The following code shows how these events can be observed:

public void onCreate(@Observes @Initialized ServletContext context) {
    System.out.println("Initialized ServletContext: " + context.getServletContextName());
}

public void onDestroy(@Observes @Destroyed ServletContext context) {
    System.out.println("Destroyed ServletContext: " + context.getServletContextName());
}

The events are emitted from a ServletContextListener called EventBridgeContextListener. You can disable lifecycle events for the ServletContext by deactivating the following class:

org.apache.deltaspike.servlet.impl.event.EventBridgeContextListener

If you manually registered the required filters and listeners, you can also simply remove the entry for the EventBridgeContextListener from your web.xml to disable the events.

Request and Response Lifecycle Events

The Servlet module also supports initialization and destruction events for the HttpServletRequest and HttpServletResponse. These events can for example be used for initialization work like invoking setCharacterEncoding on the request.

The following example shows how to observe lifecycle events for the request:

public void onCreate(@Observes @Initialized HttpServletRequest request) {
    System.out.println("Starting to process request for: " + request.getRequestURI());
}

public void onDestroy(@Observes @Destroyed HttpServletRequest request) {
    System.out.println("Finished processing request for: " + request.getRequestURI());
}

Observing lifecycle events for the response works the same way:

public void onCreate(@Observes @Initialized HttpServletResponse response) {
    System.out.println("HttpServletResponse created");
}

public void onDestroy(@Observes @Destroyed HttpServletResponse response) {
    System.out.println("HttpServletResponse destroyed");
}

All events of this category are emitted from a servlet filter called EventBridgeFilter. If you want to disable events for this category, just use DeltaSpike’s deactivation mechanism to deactivate the following class:

org.apache.deltaspike.servlet.impl.event.EventBridgeFilter

If you manually registered the required filters and listeners you can also simply remove the entry for the EventBridgeFilter from your web.xml to disable the events.

Session Lifecycle Events

The last category of events supported by the DeltaSpike Servlet module are the lifecycle events for the user’s HTTP session. The following example shows how these events can be observed from a regular CDI bean.

public void onCreate(@Observes @Initialized HttpSession session) {
    System.out.println("Session created: " + session.getId());
}

public void onDestroy(@Observes @Destroyed HttpSession session) {
    System.out.println("Session destroyed: " + session.getId());
}

The lifecycle events for the HTTP session are sent from a HttpSessionListener called EventBridgeSessionListener. To disable this event category, deactivate the following class:

org.apache.deltaspike.servlet.impl.event.EventBridgeSessionListener

If you manually registered the required filters and listeners you can also simply remove the entry for the EventBridgeSessionListener from your web.xml to disable the events.