#javaee7

Accessing HTTP Session in WebSocket endpoint

It’s possible to obtain a reference to the HttpSession within a WebSocket application using a custom implementation of ServerEndpointConfig.Configurator

Here is an example application on Github

Steps…

Override the modifyHandshakeRequest method

call the getHttpSession method on the HandshakeRequest object which is passed into the method by the WebSocket runtime

store it– one possible option is to…

Handling ‘state’ in Java WebSocket applications

By and large, there are two kinds of states in a WebSocket application

User/client specific: related to a connected user/Session e.g. user ID, list of subscriptions, last message received etc.

Global: state which is relevant across your application and something which all connected users/Sessions might be able to use

User specific state

This can be handled using getUserProperties method on the S…

Using CDI with Java EE Concurrency Utilities

This blog post explores usage of CDI along with Java EE Concurrency Utilities – specifically using CDI beans as managed tasks. Here is the sample application on Github

Lets begin with a quick overview

Java EE Concurrency Utilities provides APIs and constructs to manage concurrency within Java EE applications. Many of the Java EE components have specific concurrency semantics e.g. EJBs, JAX-RS…

Trending Meetup groups with Redis and Java EE

This is an application which displays the currently trending Meetup groups based on their (live) RSVPs feed. It’s built using Java EE 7 (uses WebSocket (both client & server APIs), (Singleton) EJB timers and CDI events to wire things up) and Redis

To run

get the code

change Redis connection details here and here

mvn clean install

deploy the WAR file in any Java EE 7 (or above) compliant container

Quick tip: managing Stateful EJBs in WebSocket endpoints

@Stateful EJBs can be injected in WebSocket endpoints (supported by the WebSocket specification). There is an one-to-one association between the WebSocket client & endpoint (which is by default) as well as the injected Stateful EJB instance, which makes it an good candidate for storing client specific state. It offers advanced semantics as compared to simple java.util.Map interface exposed by get…

WebSocket endpoint as Singleton EJB

By default …

… a WebSocket implementation creates a new (server) endpoint instance per client. In case you need a single instance, you can implement this using a custom ServerEndpointConfig.Configurator (by overriding the getEndpointInstance method)

The catch: you might have to sacrifice some of the (Java EE) platform related services like dependency injection and interceptors

More details here

Al…

Using Asynchronous timeouts in the Java WebSocket API

Sending messages in an asynchronous manner avoid blocking the sending thread. This is a great where your solution needs to scale in order to support a large number of clients.

But there is a limit on how long can we wait for the asynchronous process to complete

The Java WebSocket API gives you a few options in this regard

Async Timeout support

first and foremost, there is a notion of a timeoutand…

Dynamic provider registration in JAX-RS

The DynamicFeature class in JAX-RS (2.0) allows you to register providers

Dynamically i.e. without any pre-defined binding strategy (e.g. annotations)

Based on criteria i.e. to help decide which provider to bind to which JAX-RS resource(s)

The JAX-RS implementation detects and executes the DynamicFeature implementations at deployment time

Here is an example where we instruct the JAX-RS run time…