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build-test-cudf-java

Testing & Quality
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Build and test cudf Java bindings (cudf-java) inside a cudf devcontainer. Use when the user asks to build, compile, or test Java code in the cudf repository.

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Source SKILL.md: https://github.com/rapidsai/cudf/blob/HEAD/.agents/skills/build-test-cudf-java/SKILL.md

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Build and Test cudf-java

Prerequisites

JDK and Maven

Ensure JDK (17+) and Maven are installed:

java -version && mvn --version

If either is missing, detect the OS and install using the appropriate package manager. Hints:

  • Debian/Ubuntu (apt): sudo apt-get update -qq && sudo apt-get install -y -qq default-jdk maven
  • Fedora/RHEL (dnf): sudo dnf install -y java-17-openjdk-devel maven
  • Arch (pacman): sudo pacman -S --noconfirm jdk17-openjdk maven
  • macOS (brew): brew install openjdk@17 maven

Detect the OS by checking which package manager is available (e.g. command -v apt-get, command -v dnf, etc.) and use the matching command.

libcudf C++ with Java-required CMake flags

libcudf must be built with specific CMake flags for the Java bindings. Read java/README.md (section: "Build From Source") for the current required flags, then verify they are set:

grep -E "<FLAG1>|<FLAG2>|.." cpp/build/latest/CMakeCache.txt

If any flag is missing, reconfigure and rebuild libcudf following the build-test-cudf skill, passing the flags from the README. Ignore any flags that CMake reports as unused.

Environment setup

Before any mvn command, export these variables from the cudf/java directory. All subsequent build and test commands assume these are set.

export CUDF_CPP_BUILD_DIR=$(readlink -f ../cpp/build/latest)

Export MAVEN_OPTS based on the JDK version. --add-opens flags are required for every mvn invocation on JDK 17+ (strong encapsulation). Without them, gmaven-plugin:1.5 fails. On JDK 9-16 the flags are accepted but optional. On JDK 8 or below, do not set them — the JVM does not recognize --add-opens and will fail with Unrecognized option.

export MAVEN_OPTS="--add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/java.util.regex=ALL-UNNAMED"

Export MVN_COMMON_OPTS to match the CI build configuration in java/ci/build-in-docker.sh. For example:

export MVN_COMMON_OPTS="-DCUDF_CPP_BUILD_DIR=$CUDF_CPP_BUILD_DIR -DBUILD_SHARED_LIBS=OFF -DCUDF_USE_PER_THREAD_DEFAULT_STREAM=ON -DCUDA_STATIC_CUFILE=ON -DCUDF_JNI_LIBCUDF_STATIC=ON"

Building cudf-java

The Java JNI native code must be compiled for the same CUDA architectures as libcudf. Detect what libcudf was built with:

grep CMAKE_CUDA_ARCHITECTURES cpp/build/latest/CMakeCache.txt

Update MVN_COMMON_OPTS to use that value for -DCMAKE_CUDA_ARCHITECTURES (by default use NATIVE).

export MVN_COMMON_OPTS=$MVN_COMMON_OPTS -DCMAKE_CUDA_ARCHITECTURES=<VALUE>

rm -rf target/cmake-build  # only needed if changing CMAKE_CUDA_ARCHITECTURES from a previous build
mvn install $MVN_COMMON_OPTS -DskipTests

Notes:

  • Omit rm -rf target/cmake-build on incremental rebuilds when architectures haven't changed.
  • The native compilation is the slow step. Subsequent runs reuse cached artifacts if target/cmake-build is preserved.

Running Java tests

Always run mvn install -DskipTests first (see Building section above) before running tests. The mvn test goal re-triggers the cmake/native build step. If target/cmake-build already contains fully built artifacts from a prior mvn install, this is an incremental no-op. But if the cmake-build directory was cleaned or is missing, mvn test may hit a race condition where the linker tries to link libcudfjni.so before libarrow.a is fully built, causing a cannot find libarrow.a error. If this happens, re-run mvn install -DskipTests to rebuild the native code cleanly, then retry mvn test.

All tests

mvn test $MVN_COMMON_OPTS

Discovering tests

Java test sources are at java/src/test/java/ai/rapids/cudf/. Use find or glob to discover test classes:

find java/src/test/java -name "*Test.java" | head -20

Specific test class

mvn test $MVN_COMMON_OPTS \
  -Dtest="ai.rapids.cudf.ast.<ClassName>" \
  -pl .

Specific test method

mvn test $MVN_COMMON_OPTS \
  -Dtest="ai.rapids.cudf.ast.<ClassName>#<testName>" \
  -pl .

Known pre-existing failures

ArrowColumnVectorTest may show errors on JDK 21+ due to Netty/Arrow module access restrictions. These are unrelated to cudf code changes.