Working with JSON
Explore how to use the Jackson library for JSON processing in Java. Discover serialization and deserialization of Java objects, handling JSON files, customizing key mappings with annotations, working with JSON arrays, and traversing JSON trees. This lesson equips you to manage data exchange in modern applications.
Modern applications rarely live in isolation. Whether we are building a web server, reading configuration files, or communicating with a database, our Java programs constantly need to exchange data with other systems. These systems might not run on Java, so we need a universal language to bridge the gap. That language is JSON (JavaScript Object Notation).
Java SE does not include a built-in JSON binding library in the JDK. Some Java ecosystems use Jakarta JSON-P or JSON-B, but many professional projects rely on third-party libraries like Jackson. Instead, most professional projects rely on robust, lightweight third-party libraries. In this lesson, we will master Jackson, the most popular library for converting data between Java memory and JSON text.
Prerequisite: Add the Jackson Databind dependency (
com.fasterxml.jackson.core:jackson-databind), which includesjackson-coreandjackson-annotations.
What Is JSON and Why Jackson?
JSON is a text-based format that represents data as key-value pairs. It is lightweight, human-readable, and language-independent.
In Java, we work with strong types like User, Product, or List<String>. To send this data over a network or save it to a file, we must convert it into a JSON string. This process is called serialization. Conversely, when we receive JSON text, we must convert it back into Java objects, a process called deserialization.
The Jackson library acts as a translator. At its core is the ObjectMapper class. This powerful utility automatically maps our class fields, getters, and constructors to JSON keys.
Serializing objects (writing JSON)
To convert a Java object into JSON, we use the ...