Core Java

How To Make a Maven Build Fast

Efficient build processes are crucial for software development projects. When working with Apache Maven, a build automation tool for Java projects, you may discover that build times pose a significant challenge as projects increase in size and complexity. In this guide, we’ll explore various strategies to help us significantly enhance the speed of our Maven builds.

1. Background on Maven

Apache Maven is an open-source build automation and project management tool in the Java software development ecosystem that helps to manage and build projects more efficiently.

Developers specify their project’s configuration in the pom.xml file, and Maven takes care of the rest tasks such as:

  • Dependency ManagementMaven simplifies the process of managing project dependencies in a configuration file named pom.xml that automatically downloads and manages dependencies from remote repositories.
  • Build Lifecycle: Maven defines a series of build phases (e.g., compile, test, package, install, deploy) that we can execute to perform various build tasks, such as compiling source code, running tests, and deploying artifacts.
  • Project Management: Maven simplifies the management of project metadata, such as version numbers, project descriptions, and dependencies.
  • Plugin System: Maven allows us to extend and customize the build process by creating and configuring plugins.
  • Uniform Build System: Maven ensures that if a project builds successfully on one developer’s machine, it is likely to build successfully on others as long as they use the same configuration.

2. Common Reasons Why Maven Builds Takes Longer

Here are some common reasons for slow Maven builds:

  • Large Test: If a project has a large number of tests or integration tests, running them can add considerable time to the build process.
  • Clean Builds vs. Incremental Builds: Clean builds mvn clean install take longer than incremental builds mvn install because they delete existing build artifacts and start from scratch.
  • Number of Dependencies: Projects with a high number of dependencies can lead to longer build times because Maven needs to download and resolve all the dependencies, which can be time-consuming.
  • Plugin Mis-Configuration: Poorly configured plugins can significantly impact build performance.
  • Slow Internet Connection: If your build process relies on downloading dependencies from remote repositories, a slow internet connection can significantly increase build times but only for first time builds. A slow internet connection won’t affect the maven build time if the project has already downloaded dependencies and plugins, and your local repository is up to date.

3. Tips for Improving Maven Build Performance

Speeding up a Maven build can significantly improve our development workflow and save us valuable time. Below are suggestions and best practices to make Maven builds faster:

3.1 Use Multiple Threads for Parallel Builds

Maven 3.0 and later versions support parallel builds. By specifying the number of threads, Maven can build modules concurrently thereby speeding up the overall build process. To enable this feature, set the --threads flag when invoking Maven.

We have the option to explicitly define the precise number of threads for our project’s build like this:

mvn clean install -T 4

In the example above, Maven will use 4 threads for the build.

Alternatively, we have the option to specify the thread count based on the available CPUs on our machine like this:

mvn -T 1C clean install

The above example will use 1 thread per available CPU core.

3.2 Build Only Necessary Modules

If we have quite a large project, we can employ an incremental build approach. This means that only the modified source files and the dependencies associated with them will be recompiled, which can save a significant amount of time during the development process.

For example, the command below only builds moduleName1 and moduleName2 and any module they depend on which helps to avoid building the entire project each time changes are made in a multi-module Maven project.

mvn clean install -pl moduleName1, moduleName2 -am

3.3 Limit Internet Access (Offline Mode)

Maven provides an offline mode that can be helpful if you frequently build your project without changing dependencies. By running Maven in offline mode, you prevent it from connecting to remote repositories to check for updates.

To use offline mode, run the following command:

mvn clean install -o

Exercise caution when using this command, especially if you want to ensure that you have the latest dependencies.

3.4 Use the Maven Daemon

The Maven Daemon project intends to accelerate Maven builds especially useful in large codebase projects. It serves as a long-living background process (daemon) that keeps key elements of a Maven project in memory, allowing for faster subsequent builds.

How to Install mvnd contains installation instructions on how to install Maven Daemon on your system.

To use mvnd, we just need to execute the mvnd command instead of using the regular mvn command when building our Maven project. For example:

mvnd clean install

The above command initiates the mvnd daemon process in the background and proceeds to execute the clean and install goals of our Maven build.

3.5 Use the -DskipTests or -Dmaven.test.skip Flags

During development, we can skip running tests with the -DskipTests or -Dmaven.test.skip flags. Temporarily disabling tests can speed up the build process, especially when making frequent small changes.

To skip test execution in our Maven projects, we can use the following command:

mvn clean install -DskipTests

To skip test compilation and execution, we can also use the following command:

mvn clean install -Dmaven.test.skip=true

3.6 Use a Repository Manager

A repository manager is a dedicated server designed to facilitate the storage, retrieval, and management of software artifacts and dependencies used in software development and distribution. It acts as a local cache, proxying remote repositories while also allowing us to host our internal artifacts.

Some popular repository managers for Maven are Nexus, Sonatype Nexus, and JFrog Artifactory.

We can set up a repository manager to cache dependencies locally to reduce download times and improve the build speed of our Maven projects. Here is how to use a repository manager to make our Maven builds faster:

  • Select and Install a Repository Manager: Follow the installation and configuration instructions provided by your chosen repository manager.
  • Configure Your Maven Settings: Modify your Maven settings to use the repository manager as the primary repository for dependencies. You can do this by editing the settings.xml file in your Maven installation, located in the conf directory. Adding a <mirrors> section to settings.xml as shown below redirect requests to your chosen repository manager:

3.7 Optimize Plugin Configuration

Plugins that are not configured properly can slow down our Maven build process. We should ensure that we only use plugins necessary for our project. We also need to pay attention to plugin execution phases and profiles, and eliminate any redundancies or unused configurations.

Additionally, each Maven plugin may have various configurations that may impact build times. Examine the configuration of plugins within our project’s pom.xml file to determine if we can optimize any of them.

3.8 Maven Profile Configuration

By using Maven profiles, we can make our Maven build faster by specifying customizations and configurations for different build environments. For example, we can configure a profile to skip certain resources or test executions which can significantly speed up the build process or we might have a profile for development that includes additional dependencies for testing but excludes them in a production profile to make the build faster.

3.8.1 Selective Test Execution

We can create a profile to skip certain tests during the build. This can significantly reduce the build time, especially during development. We can add a profile for skipping tests in our projects pom.xml like this:


3.9 JVM Settings

The JIT (Just-In-Time) compiler can be configured to optimize code compilation thresholds. We can experiment with options like -XX:CompileThreshold to find an optimal value for our project.

The JVM also supports tiered compilation, which can be enabled with the -XX:+TieredCompilation flag to help optimize the startup time which can improve the overall performance of the build process.

We can set the JVM parameters to instruct the JVM to perform only essential JIT compilation by setting the MAVEN_OPTS in our project like this:

export MAVEN_OPTS="-XX:+TieredCompilation -XX:TieredStopAtLevel=1";

4. Conclusion

In this article, we discussed some reasons why Maven builds might take longer to complete. We also explored some strategies and best practices to make a Maven build faster, which can have a substantial impact on our development workflow.

In conclusion, speeding up a Maven build is a critical aspect of improving development efficiency. Applying the strategies discussed in this article can help reduce build times and improve developer productivity.

Omozegie Aziegbe

Omos holds a Master degree in Information Engineering with Network Management from the Robert Gordon University, Aberdeen. Omos is currently a freelance web/application developer who is currently focused on developing Java enterprise applications with the Jakarta EE framework.
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Back to top button