Build lifecycle phases

Maven’s default build lifecycle consists of several phases, each responsible for a specific step in building, testing, and deploying your project. Here’s a detailed explanation of the key phases:

validate
- Purpose: The validate phase checks if the project structure is correct and verifies that all necessary information (like the pom.xml configuration) is available. It’s the very first step in the build process.
- What Happens: Ensures that the project’s directory structure meets Maven’s standards. Checks that all required configurations and dependencies are specified.
- Example: If a required property is missing in your pom.xml, validate will catch it before any further processing.
compile
- Purpose: The compile phase compiles the project’s source code into bytecode (typically producing .class files).
- What Happens: Maven invokes the maven-compiler-plugin (or another compiler plugin) to transform your Java source `code into compiled code. This phase only deals with main source code, not test code.
- Example: Your Java files in src/main/java are compiled into the target/classes directory.
test
- Purpose: The test phase runs the unit tests to ensure the compiled code works as expected.
- What Happens: Maven uses the maven-surefire-plugin to execute tests. It runs tests located in src/test/java (or another specified location) against the compiled code. This phase is crucial for catching errors early, ensuring that changes haven’t broken the functionality.
- Example: JUnit tests are executed, and if any tests fail, the build process stops (unless configured to continue).
package
- Purpose: The package phase takes the compiled code and packages it into a distributable format.
- What Happens: The project is packaged into a JAR, WAR, or another archive format. Plugins like the maven-jar-plugin or maven-war-plugin are used to create the final artifact.
- Example: After compiling and testing, your application is packaged as a my-app.jar or my-webapp.war file in the target directory.
install
- Purpose: The install phase installs the packaged artifact into your local Maven repository.
- What Happens: The artifact (e.g., JAR or WAR) is copied to your local repository (typically located in your user home directory under .m2/repository). This allows you to use your built artifact as a dependency in other local projects.
- Example: If you build a library project, after running mvn install, other projects on your machine can reference that library by its group ID, artifact ID, and version.
deploy
- Purpose: The deploy phase is used in a distributed development environment to copy the final package to a remote repository.
- What Happens: The artifact is uploaded to a remote repository manager (like Nexus, Artifactory, or another Maven repository server). This makes the artifact available for other developers and projects within your organization.
- Example: When you run mvn deploy in a CI/CD pipeline, your application is automatically published to your company’s remote repository for shared use.

Summary

validate: Ensures the project setup is correct.
compile: Compiles your source code.
test: Executes unit tests to verify code correctness.
package: Bundles the compiled code into a distributable format.
install: Installs the package into the local repository.
deploy: Publishes the package to a remote repository for broader use.

Each phase is designed to work sequentially, ensuring a smooth and automated transition from source code to a deployed artifact, with testing and packaging integrated into the process.