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Standalone Nexus Operations - Java SDK

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Standalone Nexus Operations let you run Nexus Operation Executions independently, without being orchestrated by a Workflow. Instead of calling a Nexus Operation from within a Workflow Definition using Workflow.newNexusServiceStub(), you execute a Standalone Nexus Operation directly from a Nexus service client created from a NexusClient using NexusClient.newNexusServiceClient().

Standalone Nexus Operations use the same Nexus Service contract, Operation handlers, and Worker setup as Workflow-driven Operations — only the execution path differs. See the Nexus feature guide for details on defining a Service contract, developing Operation handlers, and registering a Service in a Worker.

This page focuses on the client-side APIs that are unique to Standalone Nexus Operations:

info

This documentation uses source code from the Java Nexus Standalone sample.

Prerequisites​

Standalone Nexus Operations are at Pre-release and require a special Temporal CLI build.

1. Install and verify the Pre-release Temporal CLI​

The temporal nexus operation commands require a Pre-release build of the Temporal CLI. See Temporal CLI support for the platform downloads, then verify:

./temporal --version
# temporal version 1.7.4-standalone-nexus-operations

Run it as ./temporal from the directory where you extracted it. The standard brew install temporal build does not include Standalone Nexus Operation support during Pre-release.

2. Start a local dev server​

The Pre-release dev server enables Standalone Nexus Operations by default — no dynamic config is required. Start it with the caller and handler Namespaces pre-created:

./temporal server start-dev \
  --namespace my-caller-namespace \
  --namespace my-handler-namespace

The starter and Worker connect to two different Namespaces (a caller Namespace and a handler Namespace), mirroring how Nexus crosses Namespace boundaries.

To run the examples on this page against the Java sample, create a Nexus Endpoint that routes to the handler Namespace and the Worker's Task Queue:

./temporal operator nexus endpoint create \
  --name my-nexus-endpoint \
  --target-namespace my-handler-namespace \
  --target-task-queue nexus-handler-queue

Start the sample handler Worker in the handler Namespace:

TEMPORAL_NAMESPACE=my-handler-namespace \
  ./gradlew -q :core:execute -PmainClass=io.temporal.samples.nexusstandalone.handler.HandlerWorker

Run the starter in the caller Namespace (from a separate terminal):

TEMPORAL_NAMESPACE=my-caller-namespace \
  ./gradlew -q :core:execute -PmainClass=io.temporal.samples.nexusstandalone.StandaloneClientStarter

Execute a Standalone Nexus Operation​

To execute a Standalone Nexus Operation, first create a NexusClient, then derive a typed NexusServiceClient from it with newNexusServiceClient(), bound to a specific Nexus Endpoint and Service. The endpoint must be pre-created on the server. Then call start() or execute() from application code (for example, a starter program), not from inside a Workflow Definition.

execute() waits for the Operation to complete and returns the result. Both methods take a StartNexusOperationOptions whose id is required — the SDK never generates one for you. scheduleToCloseTimeout is optional and defaults to the maximum allowed by the Temporal server.

NexusClient nexusClient = NexusClient.newInstance(stubs, options);
NexusServiceClient<GreetingNexusService> greetingClient =
    nexusClient.newNexusServiceClient(GreetingNexusService.class, ENDPOINT_NAME);

// Block until the operation completes and return its result.
GreetingOutput greeting =
    greetingClient.execute(
        GreetingNexusService::greet,
        StartNexusOperationOptions.newBuilder()
            .setId("greet-" + UUID.randomUUID())
            .setScheduleToCloseTimeout(Duration.ofSeconds(10))
            .build(),
        new GreetingInput("World"));

executeAsync() is the same but returns a CompletableFuture instead of blocking.

CompletableFuture<GreetingOutput> future =
    greetingClient.executeAsync(
        GreetingNexusService::greet, options, new GreetingInput("World"));
GreetingOutput greeting = future.get();

See the full starter sample for a complete example that executes both synchronous and asynchronous Operations, gets their results, and lists and counts Operations.

Or use the Temporal CLI to execute a Standalone Nexus Operation:

./temporal nexus operation execute \
  --namespace my-caller-namespace \
  --endpoint my-nexus-endpoint \
  --service GreetingNexusService \
  --operation greet \
  --operation-id my-greet-op \
  --input '{"name":"World"}'

Start a Standalone Nexus Operation and Wait for the Result​

start() returns a NexusOperationHandle. Use NexusOperationHandle.getResult() to wait until the Operation completes and retrieve its result. This works for both synchronous and asynchronous Operations.

// Start an operation and get a NexusOperationHandle.
NexusOperationHandle<GreetingOutput> handle =
    greetingClient.start(
        GreetingNexusService::startGreeting, options, new GreetingInput("World"));

// Block until the operation completes and retrieve its result.
GreetingOutput greeting = handle.getResult();

If the Operation completed successfully, the result is returned. If the Operation failed, the failure is thrown as a NexusOperationException. Use getResultAsync() for a non-blocking CompletableFuture, or getResult(long timeout, TimeUnit unit) to bound the wait.

Or use the Temporal CLI to wait for a result by Operation ID:

./temporal nexus operation result --namespace my-caller-namespace --operation-id my-greet-op

List Standalone Nexus Operations​

Use NexusClient.listNexusOperationExecutions() to list Standalone Nexus Operation Executions that match a List Filter query. The result is a Stream of operation metadata entries.

Note that listNexusOperationExecutions() is called on a NexusClient, not on the typed NexusServiceClient.

String query = "Endpoint = \"" + ENDPOINT_NAME + "\"";
nexusClient
    .listNexusOperationExecutions(query)
    .forEach(
        op ->
            System.out.printf(
                "OperationId: %s, Operation: %s, Status: %s%n",
                op.getOperationId(), op.getOperation(), op.getStatus()));

The query parameter accepts List Filter syntax. For example, "Endpoint = 'my-endpoint' AND ExecutionStatus = 'Running'".

Or use the Temporal CLI:

./temporal nexus operation list --namespace my-caller-namespace --query 'Endpoint = "my-nexus-endpoint"'

Count Standalone Nexus Operations​

Use NexusClient.countNexusOperationExecutions() to count Standalone Nexus Operation Executions that match a List Filter query.

Note that countNexusOperationExecutions() is called on a NexusClient, not on the typed NexusServiceClient.

String query = "Endpoint = \"" + ENDPOINT_NAME + "\"";
NexusOperationExecutionCount count = nexusClient.countNexusOperationExecutions(query);
System.out.println("Total Nexus operations: " + count.getCount());

Passing a GROUP BY query (for example, "GROUP BY ExecutionStatus") returns a count per group, available through NexusOperationExecutionCount.getGroups().

Or use the Temporal CLI:

./temporal nexus operation count --namespace my-caller-namespace --query 'Endpoint = "my-nexus-endpoint"'

Run Standalone Nexus Operations with Temporal Cloud​

The code samples referenced on this page build their client from a ClientConfigProfile loaded from a TOML profile, so the same code works against Temporal Cloud — just point the profile at your Cloud Namespace (or override the connection via TEMPORAL_* environment variables). No code changes are needed.

For full details on connecting to Temporal Cloud, including Namespace creation, Nexus Endpoint setup, certificate generation, and authentication options, see Make Nexus calls across Namespaces in Temporal Cloud and Connect to Temporal Cloud.