The book is what it says it is - a handbook, a quick reference, a fast track guide. It covers the nitty gritty of the Java WebSocket API which is a standard (specification) for building WebSocket applications. It is targeted (primarily) towards Java/Java EE developers and can be used in various capacities

• As a getting started with the Java WebSocket API guide
• You are already well versed with this API and its constructs, but need a quick peek/reference to a specific API, it's usage, nuances etc.
• Maybe you're just curious about what Java has to offer in terms of WebSocket support - feel free to check this out

The first three lessons are meant to get your feet wet

• Warm up
• API Overview
• Programming Model

Then comes the core part which is important from a API usage perspective

• Sending Messages
• Receiving Messages
• WebSocket Client API

The default conventions offered by the WebSocket API can actually hide the details related to Configuration & Deployment, but you should know them anyway ! 

• Configuration
• Deployment

The book ends with a exploration of how the API integrates with other Java EE specifications as well as a quick peek into the threading details of some of the API constructs

• Tying in with the Java EE Platform: Part I (EJB, CDI) and II (Servlet, Security)
• Lifecycle and Concurrency semantics

It is not meant to be ...

• a generic discourse on WebSocket: it deals with the Java implementation of the WebSocket specification (JSR-356 to be specific)
• a deep dive into the WebSocket RFC
• exploration of other Java based WebSocket APIs/frameworks (e.g. Atmosphere etc.) is not the goal of this book

EJBs are not about XMLs and interfaces any more. They offer a simplified, declarative and POJO based programming model powered by annotations. These are used by the the container to weave its magic at runtime. In other words, the container does all the heavy lifting for you once you communicate your requirements via annotations.

This book consists of short chapters, each of which cover a specific part of the EJB specification. Here is a comprehensive list - life cycle management, dependency & resource injection, pooling, concurrency, web services, interceptors, security, transactions, schedulers & timers, asynchronous model, eager initialization, heterogenous interfaces/views and exception handling.

The content of this book are divided into distinct sections which cover the bare basics, core components and some of the advanced framework features as well. Here is a snapshot

• JAX-RS 2.1 (latest addition) - Server Sent Events, JSON-B integration, Reactive Client API etc.
• Core: resources, annotations, HTTP method dispatch, injection
• Providers: message body readers & writers, filters, interceptors, exception mappers
• Advanced: request processing pipeline, method matching, caching, content negotiation
• Other topics: Asynchronous processing, Client API, Security