Maven Dependencies vs Maven Plugins
Two important concepts in Maven are dependencies and plugins. While both are crucial for building a successful project, they serve different purposes. In this blog post, we’ll explore the difference between Maven dependencies and plugins, and when to use each one.
Maven Dependencies
Maven dependencies are external libraries that a project relies on to compile and run. These can be third-party libraries or other projects in the same organization. Dependencies are declared in the project’s pom.xml file, along with their version numbers and scopes. Scopes determine when the dependencies are available in the build process. The most commonly used scopes are compile, test, and runtime.
The compile scope is used for dependencies that are needed at compile time and runtime. These dependencies are included in the final package. The test scope is used for dependencies that are only needed for testing. These dependencies are not included in the final package. The runtime scope is used for dependencies that are needed at runtime but not at compile time. These dependencies are not included in the final package.
For example, suppose your project needs to use the popular Guava library. You would add the following dependency to your pom.xml file:
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<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>30.1.1-jre</version>
</dependency>
Maven will automatically download the Guava library and include it in your project’s classpath.
Maven Plugins
Maven plugins are extensions to the build process that perform specific tasks. Plugins are executed in a specific order during the build process, based on their configured phases. Each plugin can have multiple goals, which are the specific tasks that the plugin performs. Plugins are declared in the pom.xml file, just like dependencies.
For example, the maven-compiler-plugin is used to compile Java source code. Here is an example of how to configure the plugin in the pom.xml file:
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<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
This configuration sets the source and target versions to 1.8, which is the default for Maven.
When to Use Dependencies vs Plugins
In general, dependencies are used to provide libraries that your code depends on, while plugins are used to execute specific build tasks. However, there are some cases where the line between dependencies and plugins can be blurred.
For example, suppose you need to run a script as part of your build process. You could use a dependency to include the script file in your project, and then use a plugin to execute the script. In this case, the dependency is providing the content of the script, while the plugin is executing it.
In general, it’s best to use dependencies for code that is directly used by your project, and plugins for build tasks that are not directly related to your code. This helps keep your pom.xml file organized and easy to read.
Conclusion
Maven dependencies and plugins are both important parts of the Maven build process. Dependencies are used to provide libraries that your code depends on, while plugins are used to execute specific build tasks.