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= Kudu Java client example README
:author: Kudu Team
:homepage: https://kudu.apache.org/

This is an example program that uses the synchronous Kudu Java client APIs to

- Create a table
- Insert some rows
- Alter the table
- Scan some rows
- Delete the table

== Building for client application development

If you are developing a Kudu client application and want to use published Kudu
artifacts from Maven Central, ensure maven is installed and from the java-example
directory run:

[source,bash]
----
$ mvn package
$ java -jar target/kudu-java-example-1.0-SNAPSHOT.jar
----

This will:

- Download `kudu-client` and all dependencies from Maven Central
- Download `kudu-binary` (mini-cluster binaries) for running unit tests
- Run unit tests using the packaged mini-cluster
- Build the executable JAR

By default, the example assumes the Kudu cluster has a single master running on
localhost with the default port 7051. To specify a different set of masters for
Kudu cluster, set the property `kuduMasters` to a CSV of the master addresses in
the form `host:port`, as shown:

[source,bash]
----
$ java -DkuduMasters=master-0:7051,master-1:7051,master-2:7051 -jar target/kudu-java-example-1.0-SNAPSHOT.jar
----

== Building for Kudu development (using locally built binaries)

If you are developing Kudu itself and have built it from source, you should use your
locally built Kudu client and binaries. This ensures you're testing against your
local changes rather than the published versions from Maven Central.

First, publish your local build to your local Maven repository:

[source,bash]
----
$ cd $KUDU_HOME/java
$ ./gradlew publishToMavenLocal
----

Then build the example with the `-DuseLocalKuduBin=true` property. You must also
specify the Kudu version via `-Dkudu-version` to match your local build (found in
`$KUDU_HOME/version.txt`, e.g., `1.19.0-SNAPSHOT`):

[source,bash]
----
$ cd $KUDU_HOME/examples/java/java-example
$ mvn package -DuseLocalKuduBin=true -Dkudu-version=$(cat "$KUDU_HOME/version.txt")
----

This will:

- Use the locally published `kudu-client` from `~/.m2/repository`
- Skip downloading the `kudu-binary` artifact (large, only in releases)
- Run unit tests using your local Kudu binaries (auto-discovered via PATH or `which kudu`)
- Build the executable JAR

If `kudu` is not in your PATH, you can explicitly specify the binary directory:

[source,bash]
----
$ mvn package -DuseLocalKuduBin=true \
    -Dkudu-version=1.19.0-SNAPSHOT \
    -DkuduBinDir=$KUDU_HOME/build/latest/bin
----