# Jersey CDI Container Agnostic Support

## Introduction

At the time of this writing, Java SE support is being discussed as one of important additions to CDI 2.0 specification. Existing CDI implementations brought this feature already, only container bootstrapping has not yet been standardized. In Jersey version 2.15 we introduced Weld SE support, so that people could take advantage of CDI features also when running in Java SE environment. As part of this work, the old Jersey CDI module has been refactored so that it supports CDI integration in any CDI-enabled HTTP container.

This chapter is mainly focused on server-side Jersey Weld SE support. We will mention other containers that are known to be working with Jersey CDI integration modules. We will also describe features demonstrated in Jersey HelloWorld Weld example and provide some hints on how to enable Java SE support for other (non Weld) CDI implementations.

## Containers Known to Work With Jersey CDI Support

To stick with JAX-RS specification, Jersey has to support JAX-RS/CDI integration in Java EE environment. The two containers supporting JAX-RS/CDI integration out of the box are Oracle GlassFish and Oracle WebLogic application server.

Apache Tomcat is another Servlet container that is known to work fine with Jersey CDI support. However, things do not work there out of the box. You need to enable CDI support in Tomcat e.g. using Weld. Jersey &jersey.github.cdi.webapp.example.link; shows how a WAR application could be packaged (see `tomcat-packaging` profile in the pom file) in order to enable JAX-RS/CDI integration in Tomcat with Jersey using Weld.

If not bundled already with underlying Servlet container, the following Jersey module needs to be packaged with the application or otherwise included in the container class-path:

    <dependency>
        <groupId>org.glassfish.jersey.ext.cdi</groupId>
        <artifactId>jersey-cdi1x</artifactId>
        <version>&version;</version>
    </dependency>

## Request Scope Binding

There is a common pattern for all above mentioned containers. Jersey CDI integration builds upon existing CDI/Servlet integration there. In other words, in all above cases, Jersey application must be deployed as a Servlet, where the underlying Servlet container has CDI integrated already and CDI container bootstrapped properly.

The key feature in CDI/Servlet integration is proper request scope binding. If this feature was missing, you would not be able to use any request scoped CDI beans in your Jersey application. To make Jersey work with CDI in containers that do not have request scope binding resolved, some extra work is required.

To allow smooth integration with Jersey request scope a new SPI, &jersey.server.spi.ExternalRequestScope;, was introduced in Jersey version 2.15. An SPI implementation should be registered via the standard `META-INF/services` mechanism and needs to make sure CDI implentation request scope has been properly managed and request scoped data kept in the right context. For performance reasons, at most a single external request scope provider is allowed by Jersey runtime.

## Jersey Weld SE Support

The extra work to align HTTP request with CDI request scope was already done by Jersey team for Weld 2.x implementation. In order to utilize Jersey/Weld request scope binding, you need to use the following module:

    <dependency>
        <groupId>org.glassfish.jersey.ext.cdi</groupId>
        <artifactId>jersey-weld2-se</artifactId>
        <version>&version;</version>
    </dependency>

Then you could use your CDI backed JAX-RS components in a Jersey application running in Grizzly HTTP container bootstrapped as follows:

Bootstrapping Jersey application with Weld support on Grizzly

                Weld weld = new Weld();
                weld.initialize();

                final HttpServer server = GrizzlyHttpServerFactory.createHttpServer(URI.create("http://localhost:8080/weld/"), jerseyResourceConfig);

                // ...

                server.shutdownNow();
                weld.shutdown();

The above pattern could be applied also for other Jersey supported HTTP containers as long as you stick with CDI Weld 2.x implementation. You simply add the above mentioned `jersey-weld2-se` module into you class-path and bootstrap the Weld container manually before starting the HTTP container.