A framework offers a set of libraries, tools, and programs to support developers and creators in achieving goals like designing an application. For example, if they want to create a RESTful web application, Java REST clients and frameworks provide libraries and functions that make it easier to code the applications’ frontend, backend, or both. Frameworks remove the complexities of managing the individual operations related to the designing of web applications and offer boilerplate code to simplify the programming logic.

Depending on the complexity and requirements, frameworks can have a single or many libraries. It can also be a set of configuration files and tools such as transpilers, compilers, and other programs. When it comes to building RESTful APIs, various frameworks in Java, Node.js, Python, etc., are available to streamline the application development processes across the client and server-side sub-systems. However, Java REST clients and frameworks are the most common and straightforward way for building RESTful applications.

In this article, you will gain information about Java REST Clients & API Frameworks. You will also gain a holistic understanding of API, REST API, its methods, Java Frameworks, and the best Java REST Clients and API Frameworks. Read along to find out in-depth information about Java REST Clients and API Frameworks.

Introduction to API

Java REST Clients and API Frameworks - API
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API stands for ‘Application Programming Interface.’ It is a set of rules that facilitate communication between two applications, allowing developers to build interactive and scalable applications. With APIs, developers can save time by taking advantage of a platform’s implementation and reducing the amount of code. APIs also help create more consistency across apps for the same platform. 

APIs are like a contract between the program’s requester (the client) and the responder (aka the server). If a requester sends X to a responder, the responder will give the requester Y. Both X and Y will be explained in the documentation for the API and specified in the contract between the two parties.

APIs can be used to create programs like a library (e.g., Python API), an Operating System, or a web server (a web API). One key advantage of an API is that developers or requesters don’t need to know the inner workings of the software. Instead, they only have to provide data to the client, enabling services using different technologies to communicate in a standard way.

Introduction to REST API

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REST API stands for Representational State Transfer, which presents some constraints of the REST architecture style. It is an architectural style for designing networked applications (i.e., apps that use a network to communicate). An HTTP request is used to access and use the data with commands such as PUT, GET, DELETE, POST, etc. 

A REST API, basically defines how different applications communicate over HTTP.  These different components remain loosely coupled and the transfer of information is fast and carried out efficiently. Since data formats aren’t defined, it serves a more diverse purpose and is easier to develop. Thus, REST APIs are a popular choice among web developers and have emerged as the standard protocol for web-based APIs.

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The REST architecture can be understood as follows:

Java REST Clients and API Frameworks - REST API Architecture
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Methods of REST API

REST guidelines recommend using a specific HTTP method on a particular type of call made to the server. These HTTP methods are as follows:

1) GET

You can use the HTTP GET method to read (or retrieve) a resource representation. GET returns a representation in JSON or XML format in the safe path and an HTTP response code of 200 (OK). It most often returns a 400 (BAD REQUEST) or 404 (NOT FOUND) in an error case. 

2) POST

The POST verb is most often used for creating new resources. In particular, developers use it to create subordinate resources. On successful creation, POST returns HTTP status 201, returning a Location header with a link to the newly created resource.

3) PUT

PUT method can be used for updating the capabilities. However, you can also use PUT to create a resource where a client chooses the resource ID instead of the server.

4) PATCH

You can use the PATCH method to modify capabilities. The PATCH request only needs to contain the changes to the resource, not the complete resource. This resembles PUT, but the body has a set of instructions describing how you should modify a resource currently residing on the server to produce a new version.

5) DELETE

You can use the DELETE method to delete a resource identified by a URL. 

Understanding Java Frameworks

Java REST Clients and API Frameworks - Frameworks in Java
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Java Frameworks are platforms or bodies of reusable pre-written code used as templates by developers to create applications using the Java programming language. These frameworks are particular to the Java programming language and can only be used for developing Java software applications and programs.

Frameworks ensure developers can program applications without having to create everything from scratch. A Java framework can include a compiler, library, defined classes (such as categories of objects), functions to interact with hardware devices, and other programs used in the development process. With a solid Java framework, developers don’t have to worry about recurrent pieces of code used across a domain or application.

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Best Java REST Clients and API Frameworks

Some of the widely used Java REST Clients and API Frameworks are as follows:

1) Play Framework

Java REST Client and API Frameworks - Play Frameowrk
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Play Java Framework is a slightly conventional and unique type of framework that is RESTful by default. It follows the approach of convention over configuration. Based on the MVC pattern, Play is an Open-Source Web Application framework, and it can be written in Java and Scala. Play will be reasonably similar if you have used Django or Ruby on Rails or ASP.NET architecture since it doesn’t necessarily follow J2EE web standards.

It is a high-performance java framework because of the asynchronous processing and is built on reactive principles. Play works on statically-typed language, ensuring most errors get caught during compile time. Play2 makes it easy to integrate with Maven projects and create simple JAR files.

2) Blade

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Blade is a lightweight and high-performing Java framework with a RESTful style routing interface that allows developers to build fast web applications. Blade focuses on elegance and follows the MVC (Model-View-Controller) software design pattern. This Java framework also focuses on simplicity, allowing creators to understand the whole framework in a single day. 

It has an easy-to-understand design and has a minimal footprint i.e., the source code is less than 500kb in total. Blade is based on Java 8 hence, it doesn’t depend on any third-party libraries. With Blade, you can access a RESTful-style routing interface and deploy your application as a basic Maven project. This Java framework also has built-in security features like CSRF (Cross-Site Request Forgery) and XSS (Cross-Site Scripting)

3) Dropwizard

Java Clients and REST API frameowrks - Dropwizard Framework
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Java Clients and REST API frameowrks - Dropwizard Framework
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Dropwizard framework is suitable for creating Java Microservices and for the rapid development of RESTful Web services. It provides access to several Java libraries to provide developers with a fast and distraction-free development platform.

Dropwizard comes with a Google Guava, an embedded Jetty server, Logback, Joda Time, Hibernate Validator, and many other popular Java libraries. Additionally, Dropwizard also contains Jackson for processing JSON and Jersey, with which you can build RESTful web services. 

4) Spark 

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Spark Framework is a Domain-specific Language for the Java and Kotlin programming languages. Kotlin Programming language can run on Java virtual machines, and it’s 100% interoperable with Java. With the Spark framework, creators can quickly develop microservices, REST APIs, and web applications.

Spark doesn’t follow the MVC framework but it will let you structure your application as per your requirements. As with most microframeworks, Spark has a small code base, doesn’t require writing too much boilerplate code, and needs minimal configuration. Developers can get the Spark framework up and running in just a few minutes. According to Spark’s survey, over 50% of their users used the framework to create REST APIs, which can be considered as its most popular use case. 

5) Grails

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Grails is a full-stack Java REST Client framework that is more suitable for developers who are just beginning their programming careers. Although Grails is a web framework written in Groovy programming language, it runs on the Java platform and is perfectly compatible with Java syntax. Grails is also based on the MVC design pattern.

If you already know Java, then learning Groovy is quite easy. It also uses GORM, although you can also directly use Hibernate to create RESTful applications with Grails framework. Grails has built-in support for RESTful APIs, thus making it easy to create them. You can also integrate your existing java code with Grails or write a mix of Groovy and Java code in your application.

6) Jersey

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Jersey is a Java framework for creating RESTful services that also support JAX-RS APIs. It has various useful features and utility functions that simplify the development of RESTful services. Jersey developers don’t have to worry about the low-level implementation of client-server communication since it provides an abstraction layer. 

Unlike other RESTful frameworks, Jersey allows for Chunked output, i.e., the responder can send back a response to the requester in chunks or parts. It helps transmit extensive data in pieces while the entire response is prepared.

7) Struts

Java REST Clients and API frameworks - Struts framework
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Struts is an old framework maintained and developed by the Apache Software Foundation. It is a full-featured Java web application framework with a vast community, often compared to the Spring Framework. Struts has a plugin-based architecture, and it follows the MVC software design pattern, allowing developers to create easy to maintain enterprise-level Java applications. 

Struts plugins are basic, portable JAR packages that make it possible to extend the framework to fit different project needs. It provides plugins bundled with the frameworks like REST plugin, JSON plugin, Config Browser Plugin, etc. 

Conclusion

In this article, you have learned about the best Java REST Clients and API frameworks. This article also provided information on APIs, REST APIs, its methods, Java Frameworks.

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Osheen Jain
Freelance Technical Content Writer, Hevo Data

Osheen has extensive experience in freelance writing within the data industry and is passionate about simplifying the complexities of data integration and data analysis through informative content for those delving deeper into these subjects.

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