Beam SDK for Java dependencies

The Apache Beam SDKs depend on common third-party components. These components import additional dependencies. You need to manage your dependencies for the following reasons:

Dependencies might have version collisions or incompatible classes and libraries.
Some libraries are not forward compatible. When you use these packages in your code, you might need to pin to the appropriate versions so that those versions are used when you run your pipeline.

When problems occur with dependencies, you might see unexpected behavior in the service, including errors such as NoClassDefFoundError, NoSuchMethodError, NoSuchFieldError, or FATAL ERROR in native method.

This page explains how to view the dependencies that your SDK is using and how to manage your dependencies to avoid issues.

View dependencies

To view your dependencies, either use the BeamModulePlugin.groovy file or retrieve the list by creating a new project through Maven and resolving the dependencies.

Use BeamModulePlugin.groovy to retrieve dependencies

The BeamModulePlugin.groovy file in the Beam repository lists compile and runtime dependencies for your Beam SDK version.

Use the following link to open the BeamModulePlugin.groovy file.
```
https://raw.githubusercontent.com/apache/beam/vBEAM_VERSION/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy
```
Replace BEAM_VERSION with the SDK version that you're using. The following example provides the dependencies for the 2.64.0 release: https://raw.githubusercontent.com/apache/beam/v2.64.0/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy.
Under project.ext.library, review the list of dependencies. Some dependencies in the list use version variables, such as google_cloud_bigdataoss_version. These variables are defined before the project.ext.library map definition.

Use a Maven project to resolve dependencies

You can retrieve the list of dependencies by creating a new project through Maven and then resolving the dependencies.

In your terminal or command line, use the following command to define the Beam SDK and Java versions for the new project.
```
export BEAM_VERSION=2.64.0
export JAVA_VERSION=11
```

Create the project.

mvn archetype:generate \
    -DinteractiveMode=false \
    -DarchetypeGroupId=org.apache.beam \
    -DarchetypeArtifactId=beam-sdks-java-maven-archetypes-starter \
    -DarchetypeVersion=$BEAM_VERSION \
    -DtargetPlatform=$JAVA_VERSION \
    -DartifactId=check-pipeline-dependencies \
    -DgroupId=org.apache.beam.samples

Change to the new project directory.
```
cd check-pipeline-dependencies
```

Resolve and list the dependencies.

mvn dependency:resolve && mvn -o dependency:list

Manage dependencies

To simplify dependency management, Beam provides Bill of Materials (BOM) artifacts that help dependency management tools select compatible combinations.

When you import Apache Beam, using a Bill of Material artifact is recommended. When a project import contains unspecified or ambiguous dependencies, the BOM provides the information that the SDK needs to use the correct dependency version.

Apache Beam provides two BOMs:

beam-sdks-java-bom: manages Apache Beam dependencies, which allows you to specify the version only one time
beam-sdks-java-io-google-cloud-platform-bom: manages Apache Beam, Google Cloud, and third-party dependencies

Because errors are more likely to occur when you use third-party dependencies, the beam-sdks-java-io-google-cloud-platform-bom BOM is recommended.

Import the BOM

To use a BOM, import the BOM into your Maven or Gradle dependency configuration. For example, to use beam-sdks-java-io-google-cloud-platform-bom, make the following changes in the pom.xml file of your SDK artifact. In the following examples, replace BEAM_VERSION with the appropriate Apache Beam SDK version.

Maven

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.apache.beam</groupId>
      <artifactId>beam-sdks-java-google-cloud-platform-bom</artifactId>
      <version>BEAM_VERSION</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

Gradle

dependencies {
    implementation(platform("org.apache.beam:beam-sdks-java-google-cloud-platform-bom:BEAM_VERSION"))
}

Remove version pinning

After you import the BOM, you can remove specific version pinning from your dependencies. For example, you can remove the versions associated with org.apache.beam, io.grpc, and com.google.cloud, including libraries-bom. Because the dependencies aren’t automatically imported by the BOM, don’t remove them entirely. Keep the dependency without specifying a version.

The following example shows dependencies without versions in Maven:

<dependency>
  <groupId>org.apache.beam</groupId>
  <artifactId>beam-sdks-java-core</artifactId>
</dependency>

The following example shows dependencies without versions in Gradle:

implementation("org.apache.beam:beam-sdks-java-core")

View the depenencies managed by the BOM

To see a full list of dependency versions that are managed by a specific BOM, use the Maven tool help:effective-pom by running the following command. Replace BEAM_VERSION with the appropriate Apache Beam SDK version.

mvn help:effective-pom -f ~/.m2/repository/org/apache/beam/beam-sdks-java-google-cloud-platform-bom/BEAM_VERSION/beam-sdks-java-google-cloud-platform-bom-BEAM_VERSION.pom

Resources

Beam SDKs Java Google Cloud Platform BOM in the Maven repository.