Java is a programming language widely used for web applications and mobile apps due to its robustness and scalability. Java backend developers are in high demand in the freelance market and the IT industry. The demand for Java programmers will continue to grow over time.

Here are some of the top technologies that you should learn as a freelance Java backend developer:

Spring Framework

The Spring Framework is an open-source framework that provides enterprise application development support for Java web applications. It's used by more than 3 million developers and has been downloaded more than 40 million times.

Spring provides support for dependency injection and aspect-oriented programming (AOP). It also includes JUnit testing, caching, transaction management, and web integration support.

Spring Data JPA

Spring Data JPA is a library that provides CRUD functionality for your Spring Data repositories. It's another one of those technologies that help you get up to speed with Spring quickly and easily.

The main goal of this project is to provide a complete solution for mapping from Java objects to database tables and vice versa without requiring additional XML configuration. To achieve this goal, it uses the standard Java Persistence API (JPA) under the hood, so it makes sense to look at it if you're interested in learning more about JPA itself.

Node.js

Node.js is a JavaScript runtime environment built by Ryan Dahl in 2009. It was designed for building fast network applications using non-blocking I/O APIs based on the V8 engine from the Google Chrome browser.

It allows backend developers to build scalable network programs that can handle thousands of concurrent connections at any given time without any issues related to scalability or performance issues because it uses an event looping model instead of the traditional threading model, which makes it highly scalable.

Hibernate

Hibernate is an object-relational mapping (ORM) framework for Java that simplifies data persistence for Java applications by eliminating direct SQL statements in your code. An ORM framework uses an abstraction layer to map objects in your code to tables on a database server, allowing you to interact with those objects as if they were part of your application's memory space.

This makes it easy to perform queries against databases without writing complex SQL statements or understanding how data is stored in relational databases.

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Summing-up

When it comes to backend development, multiple programming languages and tools are available. As a backend developer you have to keep an eye on what is in demand and trending. This enables you to stand above the competition. Keep on learning, practising, and building networks because networking is the key to success in your professional career.