Build automation is an important aspect of software development. In this article, we will compare the two most popular build tools for Java development: Maven and Gradle.
Make and Apache Ant
Previously, developers used the Make tool for building Java projects, and the build process was not much different from building applications in any other language. Then in 2000, the Ant (Another Neat Tool) build system was released.
Ant, like Make, uses an imperative style, but build scripts have XML syntax. Ant was developed as a build system specialized for Java projects. Ant is a Java-based build automation system and therefore it is much easier for a Java developer to extend its functionality.
Maven
However, already in 2004, a new Maven build system was proposed, which took a fresh look at the process of building Java applications. Previously, developers themselves organized the folder structure for storing source codes, resources, classpath directories, and output directories.
And therefore, the build scripts for Ant for two different applications could be very different: compilation, assembly, copying files to the output directory, etc. were prescribed separately. In Maven, a Java project always has a deliberately defined structure.
For example, the source codes should be in src/main/java, the resources for tests in src/test/resources. Maven allows you to create a file structure of a typical project with a single command. Maven also introduces the concept of "build lifecycle" with successive phases:
validate ➞ compile ➞ test ➞ package ➞ verify ➞ install ➞ deploy
Now, thanks to a fixed folder structure and a set of goals, there is no need to write and maintain a large build script and build scripts have become declarative. It has become more convenient for developers to work not only with their own code but also with third-party projects because it is clear how the source code is organized and how to build it.
There are quite a lot of libraries in the Java world, and a serious application uses hundreds of them. When using Ant, you need to add the necessary jar files to the project yourself. You also need to take care of the necessary transitive dependencies.
Maven provides dependency manager functionality and Maven Central Repository. Now, when specifying a new dependency in the build script, Maven will automatically find the necessary jar of the appropriate version and all its transitive dependencies, download them, and make sure that they get into the classpath of the project.
You can also raise your own closed internal repository, in which you can store your own or patched libraries, or standard libraries built manually.
It should be noted that Ant can be used in conjunction with the Apache Ivyproject, which also allows you to manage dependencies and work with Maven repositories.
Despite all the advantages of Maven, its declarative approach can be a disadvantage in some situations. For example, when you need to change the build lifecycle and add new goals to the build process.
Maven allows you to extend its functionality with plugins. There are many ready-made Maven plugins that solve various typical tasks, and these plugins are also available from the central repository.
However, if for some reason it is necessary to slightly change the standard lifecycle, and there is no suitable plugin, the developer will have to create his own plugin on his own.
Gradle
In 2008, the first release of the Gradle build system was released, and version 1.0 was released in 2012. The goal of the Gradle project is to preserve all the advantages of Maven, but also to give the developer more opportunities to customize the build process.
That is why Gradle build scripts are written in Groovy DSL. Gradle provides the ability to write declarative build scripts and more compact than Maven because XML is quite cumbersome. It's also easy to add non-standard logic to the build process in Gradle, it's enough to write a Groovy script, and you don't need to develop plugins.
At the same time, you can easily debug the execution of build scripts, as they are regular Groovy files. Thus, Gradle combines declarative and imperative approaches. Since version 5.0, Gradle also supports Kotlin DSL.
Gradle also supports plugins, which allows developers to exchange ready-made customizations.
Also, one of the significant advantages of Gradle is an incremental build. When the assembly is restarted, Gradle determines whether the files that are the input data for the target have changed and if not, the execution of the target is skipped, because its output artifacts have already been collected.
This gives a significant increase in build speed compared to Maven, especially on large multi-module projects. Gradle can also run Gradle daemon, a background process that avoids the cost of resources and initialization time each time the build is started.
Gradle has a convenient Gradle wrapper feature – it is an opportunity to generate shell and Windows batch scripts that automatically download the Gradle distribution of the specified version and use it to build the project.
This means that to build a Gradle project, you do not need to install Gradle separately, just installing Java is enough. And it is also quite easy to switch the project to another version of Gradle.
Choosing between Maven and Gradle
Despite the advantages of Gradle, quite a lot of projects use the Maven build system. The choice depends on the type of project and team.
Maven has been in use since 2004, so more developers are familiar with it. In addition, Maven is stable, the last major version 3 was released in 2010. Gradle has already changed significantly several times without backward compatibility, and developers had to migrate their build scripts to new versions.
In addition, not everyone is familiar with Groovy or Kotlin, so using Gradle requires additional knowledge, while Maven uses understandable XML. Therefore, the question arises, if the project began to be developed before Gradle became popular, does it make sense to migrate build scripts to Gradle.
On the other hand, more and more developers are choosing Gradle. Spring, Hibernate, and LinkedIn use Gradle. Also, the Android assembly system is Gradle, and it is popular with Android application developers.
All popular IDEs have integration with both build systems and support auto-completion when editing build scripts. A huge number of plugins have been developed for both Maven and Gradle, which allow you to add frequently used functions to the project build process.
Conclusion
From the pros and cons of each of the build systems described above, the following conclusion can be drawn. Maven is more suitable for small projects that do not require customization of the build process, and the build time of the project is not so critical. Gradle is more suitable for large-scale projects with a large number of modules, as well as for Android apps.