1. Introduction
Gradle provides two main keywords, compile and implementation, for configuring dependencies in software projects. While these keywords may seem similar, they have different implications and usage, and it’s important to understand the differences between them in order to use them effectively.
In this tutorial, we’ll discuss the difference between “implementation” and “compile” in Gradle and provide best practices for effective dependency management.
NOTE: Starting with Gradle 7.x, the “compile” configuration is no longer used directly. Instead, the “implementation” configuration is used for dependencies that are required for both compile and runtime. The “runtimeOnly” configuration is used for dependencies that are only required at runtime.
2. What Is compile in Gradle Dependency Management?
The compile keyword is one of the main keywords used in Gradle dependency management. When a dependency is configured with compile, it is included in both the compile-time and runtime classpaths. This means that the dependency is available during compilation and at runtime when the program is executed. However, including dependencies in both classpaths can lead to longer build times and increased memory usage.
Let’s consider a simple Gradle script:
dependencies {
compile group: 'org.hibernate', name: 'hibernate-core', version: '3.6.7.Final'
testCompile group: 'junit', name: 'junit', version: '4.13.2'
}
This script can also be written as:
dependencies {
compile 'org.hibernate:hibernate-core:3.6.7.Final'
testCompile 'junit:junit:4.13.2'
}
In this example, we’re including a dependency on the hibernate-core library with version 3.6.7.Final from the org.hibernate group using the compile keyword. This dependency will be included in both the compile-time and runtime classpaths.
We’re also including a dependency on the JUnit testing framework with version 4.13.2 using the testCompile keyword. This dependency will only be included in the test classpath, which is used when compiling and running tests. The testCompile keyword is a variation of the compile keyword that adds the dependency to the test classpath but not to the runtime classpath.
3. What Is implementation in Gradle Dependency Management?
The implementation keyword is a newer addition to Gradle dependency management, introduced in Gradle 3.4. When a dependency is configured with implementation, it is only included in the runtime classpath. This means that the dependency is not available during compilation and is only included in the final packaged application.
Using implementation can lead to faster build times, as Gradle does not have to process the dependency during compilation. However, it also means that the dependency cannot be used during compilation, which can lead to compatibility issues if other dependencies depend on it.
Let’s consider a simple Gradle script:
dependencies {
implementation group: 'org.hibernate', name: 'hibernate-core', version: '3.6.7.Final'
testImplementation group: 'junit', name: 'junit', version: '4.13.2'
}
Similarly, this script can be written as:
dependencies {
implementation 'org.hibernate:hibernate-core:3.6.7.Final'
testImplementation 'junit:junit:4.13.2'
}
In this example, we’re including a dependency on the hibernate-core library with version 3.6.7.Final from the org.hibernate group using the implementation keyword. This dependency will only be included in the runtime classpath and not in the compile-time classpath.
We’re also including a dependency on the JUnit testing framework with version 4.13.2 using the testImplementation keyword. This dependency will only be included in the test runtime classpath, making it available when running tests but not during compilation.
4. Difference Between compile and implementation
The main difference between compile and implementation in Gradle is that compile includes the dependency in both compile-time and runtime, while implementation only includes the dependency in runtime. This means that dependencies configured with compile are available during compilation, while dependencies configured with implementation are not.
Additionally, implementation provides better separation between the compile-time and runtime classpaths, making it easier to manage dependencies and avoid version conflicts. Choosing the right keyword can have implications for project performance, build times, and compatibility with other dependencies.
5. Best Practices for Gradle Dependency Management
To ensure effective dependency management in Gradle, we should consider a few best practices:
- Use the implementation keyword by default unless the dependency needs to be used during compilation.
- Avoid using the compile keyword, as it can lead to longer build times and increased memory usage.
- Use specific versions of dependencies instead of dynamic versioning to ensure consistent behavior across builds.
- Keep the dependency graph as small as possible to reduce complexity and improve build times.
- Regularly check for updates to dependencies and update them as necessary to ensure that the project uses the latest and most secure versions.
- Use dependency locking to ensure that builds are reproducible and consistent across different machines and environments.
6. Conclusion
In this article, we discussed the difference between compile and implementation in Gradle and how they affect the scope of dependencies in a project. We also provided examples and best practices for Gradle Dependency Management, including the use of implementation and compile keywords, as well as other best practices for managing dependencies.
By following these practices, we can ensure that our builds are reliable, efficient, and easy to maintain.
