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tags: Cadence Workflow

Cadence Java Samples on Windows

This post covers how to run the Cadence Java sample workflows on Windows.

First, you’ll need the JDK installed. If you’re using Java 11, you may run into this issue, which prints Could not determine java version from ‘11.0.1’ when you attempt to build the samples. The TLDR is that you should just downgrade to Java 8.

The Cadence Java samples use Gradle. The installation instructions for Gradle are here. I recommend the Chocolatey option as that’s used in the instructions for running the Cadence server locally. You’ll want to install Gradle before using IntelliJ so that Gradle is discoverable from the environment. Before building with Gradle on Windows, be sure to set your JAVA_HOME environment variable using these instructions.

For these samples, I used IntelliJ community edition.

Clone the Cadence Java samples repo with this command:

git clone https://github.com/uber/cadence-java-samples

Open IntelliJ and navigate to File->New->Project from Existing Sources. Select the cadence-java-samples directory. In the Import Project page, select Import project from external model, choose Gradle and then click Next->Finish.

Next, launch a Cadence server on your local machine. You can use the instructions covered in my earlier post.

Before running the samples, you need a sample domain. The Java samples’ instructions work well on Mac/Linux but may fail on Windows. To get it working, you’ll need to set a USER environment variable.

set USER=myname
gradlew.bat -q execute -PmainClass=com.uber.cadence.samples.common.RegisterDomain

This will register a domain called sample on your local Cadence instance. All workflows and activities are run within a domain. This is also a good test to make sure the Cadence server and client are working properly. Note that this domain will not need to be created again if you shut down docker using ctrl+c. If you use docker-compose down then the data will be wiped out and you’ll need to create the domain again.

With the domain created, it’s now possible to run the samples. There are instructions for running these from the command line included in the sample repo’s readme. You can also run the samples from IntelliJ directly.

Before the samples will work in IntelliJ, the same USER environment variable will need to be set in your run/debug configuration. But the configurations need to be created first so you can modify them. The easiest way I found to do this is to attempt to run one of the samples. The configuration is created and you can then modify it by going to Run->Edit Configurations and adding the USER environment variable for that application. To run/debug a sample, find the sample classes under src/main/java/com.uber.cadence.samples/hello. Right click on one of the sample classes and choose Run ‘-classname-.main()’ or Debug ‘-classname-.main()’. The first time it’s run, there will be a null pointer exception in the console. Add the environment variable, run again, and it should work.

Another way to approach this is to add the USER environment variable to your user profile and logout/login. Then you don’t have to setup configurations for each sample.

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