Excluding Transitive Dependencies with Gradle

In Gradle, when using the application plugin to generate a jar file, it's possible to encounter transitive dependencies that you may want to exclude. To accomplish this, the exclude method can be employed.

Default Behavior of Exclude

Initially, an attempt was made to exclude all instances of org.slf4j:slf4j-log4j12 using the following code:

configurations {
  runtime.exclude group: "org.slf4j", name: "slf4j-log4j12"
}

However, this resulted in the exclusion of all org.slf4j artifacts, including slf4j-api.

Customizing the Exclusions

To refine the exclusion, the group and module properties can be utilized:

configurations {
  runtime.exclude group: "org.slf4j", module: "slf4j-log4j12"
}

This approach successfully excludes only org.slf4j:slf4j-log4j12 without affecting other slf4j dependencies.

Exclude from an Individual Dependency

If the exclusion is desired for a specific dependency, the following syntax can be used:

dependencies {
  compile ('org.springframework.data:spring-data-hadoop-core:2.0.0.M4-hadoop22') {
    exclude group: "org.slf4j", module: "slf4j-log4j12"
  }
}

Limitations of the Exclude Method

It's important to note that while arbitrary properties can be specified in Exclusions, this is not permitted when excluding from individual dependencies. For instance, the following code will fail:

dependencies {
  compile ('org.springframework.data:spring-data-hadoop-core:2.0.0.M4-hadoop22') {
    exclude group: "org.slf4j", name: "slf4j-log4j12"
  }
}

with the following error message:

No such property: name for class: org.gradle.api.internal.artifacts.DefaultExcludeRule

Understanding Gradle Modules

In Gradle, the module property corresponds to the Maven artifactId. Therefore, to determine the module of a particular Maven artifact, inspect its artifactId. For example, the Maven artifact org.slf4j:slf4j-log4j12 would have a Gradle module of slf4j-log4j12.