JSON is a lightweight, text-based, platform-neutral data interchange format in which objects are represented in the attribute-value pair format. Historically, JSON originated from JavaScript. However, nowadays, it is considered to be a language-independent format because of its wide adoption by all modern programming languages. In this section, you will learn the basics of the JSON format.

The JSON format is very simple by design. It is represented by the following two data structures:

• An unordered collection of the name-value pairs (representing an object):
  • Attributes of an object and their values are represented in the name-value pair format; the name and the...

If you use Java RESTful web service frameworks, such as JAX-RS, for building RESTful web APIs, the serialization and deserialization of the request and response messages will be taken care of by the framework. However, understanding the JSON structure and tools for processing JSON will definitely help you when the default offering by the framework does not meet your requirements. The following diagram illustrates the role of the JSON marshalling (converting Java object to JSON format) and unmarshalling components (converting JSON format to Java Object) in a typical Java RESTful web service implementation:

This section will teach you the various processing models for JSON data. By the term processing, we mean reading, writing, querying, and modifying JSON data. Two widely adopted programming models for processing JSON are as follows:

• Object model: In this...

There are many Java-based frameworks available today for processing JSON. In this section, we will learn the APIs available in the Java EE platform for processing JSON. Java EE 7 has standardized the JSON processing APIs with Java Specification Request (JSR), that is, JSR 353 – Java API for JSON Processing. This JSR offers portable APIs to parse, generate, transform, and query the JSON data. The JSR 353 APIs can be classified into two categories on the basis of the processing model followed by the APIs:

• Object model API
• Streaming model API

We had a generic discussion on these two processing models in the previous section, Processing JSON data. In this section, we will see how these processing models are implemented in JSR 353.

Jackson is a multipurpose data processing Java library. The primary capability of this tool is the support for processing JSON. It also has additional modules for processing the data encoded in other popular formats, such as Apache Avro (a data serialization system), Concise Binary Object Representation (CBOR), a binary JSON format, Smile (a binary JSON format), XML, comma-separated values (CSV), and YAML. In this section, you will learn how to use Jackson APIs to process JSON.

Jackson provides the following three methods for processing JSON:

• Tree model APIs: This method provides APIs for building a tree representation of a JSON document
• Data binding API: This method provides APIs for converting a JSON document into and from Java objects
• Streaming API: This method provides streaming APIs for reading and writing a JSON document

We will...

Gson is an open source Java library that can be used for converting Java objects into JSON representations and vice versa. The Gson library was originally developed by Google for its internal use and later open sourced under the terms of Apache License 2.0.

The main class in the Gson library that you will use for building an object model from the JSON data is the com.google.gson.Gson class. Here is a list of the core Gson classes from the object model API category:

While Java EE8 is on its way and expected by the end of 2017, one of the most-awaited enhancement in Java EE 8 is related to JSON processing, covered by JSR 374 – Java API for JSON Processing 1.1.

With JSON becoming widely used in service-oriented patterns (such as reusable contract and lightweight endpoint), another key feature planned in Java EE8 is the JSR 367 Java API for JSON Binding (JSON-B). Similar to GSON, JSR 367 brings in the capability of marshalling/unmarshalling Java objects to JSON representation. JSON-B will be the standard binding layer for converting Java objects to/from JSON messages, similar to JAXB for XML binding.

In this chapter, you were introduced to the various processing models for the JSON content and some of the popular Java-based JSON processing frameworks available today. We also explored the upcoming enhancements for processing JSON in Java EE8. This chapter is essential for understanding how the JSON-based request and response messages are bound to the Java model while building REST APIs later in the book.

This chapter is not meant to recommend any specific JSON framework for your application but to help you understand the popular frameworks available today for processing JSON, and their offerings in general.

In the next chapter, we will build our first REST service by using JAX-RS APIs.