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How to create a Temporal Client in Java

To initialize a Workflow Client, create an instance of a WorkflowClient, create a client-side WorkflowStub, and then call a Workflow method (annotated with @WorkflowMethod).

To start a Workflow Execution, your Temporal Server must be running, and your front-end service must be accepting gRPC calls.

To establish a connection with the front-end service, use WorkflowServiceStubs.

WorkflowServiceStubs service = WorkflowServiceStubs.newLocalServiceStubs();

You can provide WorkflowServiceStubsOptions to override the default values for the gRPC calls.

For example, the default front-end service gRPC address is set to 127.0.0.1:7233, where 7233 is the default port for the Temporal Frontend Service.

If your server is running on a different host or port from the default, you can set it as shown in the following example.

WorkflowServiceStubs service = WorkflowServiceStubs.newInstance(
                    WorkflowServiceStubsOptions.newBuilder()
                     .setTarget(TARGET_ENDPOINT)
                            .build());

After the connection to the Temporal Frontend Service is established, create a Client for the service stub. The Workflow Client helps with client-side APIs and is required by Workers.

Create an instance of a WorkflowClient for the Workflow service stub, and use WorkflowClientOptions to set options for the Workflow Client. The following example shows how to create a WorkflowClient instance called "client" for the WorkflowServiceStubs "service" that we created in the previous example, and set Namespace option for the WorkflowClient.

WorkflowClient client = WorkflowClient.newInstance(
                service,
                WorkflowClientOptions.newBuilder()
                        .setNamespace(“Abc”)
                    .build());

For more information, see WorkflowClientOptions.

WorkflowService and WorkflowClient creation is a heavyweight operation, and will be resource-intensive if created each time you start a Workflow or send a Signal to it. The recommended way is to create them once and reuse where possible.

With the Client defined, you can start interacting with the Temporal Frontend Service.

To initialize a Workflow in the Client, create a WorkflowStub, and start the Workflow Execution with WorkflowClient.start(). Starting Workflows or sending Signals or Queries to Workflows from within a Client must be done using WorkflowStubs.

WorkflowClient workflowClient =  WorkflowClient.newInstance(service, clientOptions);
 // Create a Workflow stub.
 YourWorkflow workflow = workflowClient.newWorkflowStub(YourWorkflow.class);
 // Start Workflow asynchronously and call its "yourWFMethod" Workflow method
 WorkflowClient.start(workflow::yourWFMethod);

For more information, see the following: