Add external nexus caller example

build.gradle

@@ -26,12 +26,13 @@ subprojects {
     ext {
         otelVersion = '1.30.1'
         otelVersionAlpha = "${otelVersion}-alpha"
-        javaSDKVersion = '1.30.1'
+        javaSDKVersion = '1.31.0-SNAPSHOT'
         camelVersion = '3.22.1'
         jarVersion = '1.0.0'
     }
 
     repositories {
+        mavenLocal()
         maven {
             url "https://oss.sonatype.org/content/repositories/snapshots/"
         }

core/src/main/java/io/temporal/samples/nexusexternalcaller/README.MD

@@ -0,0 +1,32 @@
+# Nexus External Caller Sample
+
+This sample shows how to start and interact with Nexus operations from outside of a workflow.
+
+To run this sample, set up your environment following the instructions in the main [Nexus Sample](../nexus/README.md).
+
+Next, in separate terminal windows:
+
+### Nexus handler worker
+
+```
+./gradlew -q execute -PmainClass=io.temporal.samples.nexusexternalcaller.handler.HandlerWorker \
+    --args="-target-host localhost:7233 -namespace my-target-namespace"
+```
+
+### Start Nexus Operation
+
+```
+./gradlew -q execute -PmainClass=io.temporal.samples.nexusexternalcaller.caller.CallerStarter \
+    --args="-target-host localhost:7233 -namespace my-caller-namespace"
+```
+
+### Output
+
+which should result in on the caller side:
+```
+21:18:31.282 { } [main] INFO  i.t.s.n.caller.CallerStarter - Execute echo operation: Hello 
+21:18:31.299 { } [main] INFO  i.t.s.n.caller.CallerStarter - Started hello operation with token: eyJ0IjoxLCJucyI6Im15LXRhcmdldC1uYW1lc3BhY2UiLCJ3aWQiOiI3NWU0MTk2Zi05ODdiLTRhYzMtOTdiZS1hMjBiYjViOWZiNDUifQ 
+21:18:31.299 { } [main] INFO  i.t.s.n.caller.CallerStarter - Waiting for hello operation to complete... 
+21:18:31.311 { } [main] INFO  i.t.s.n.caller.CallerStarter - Hello operation result: Hello Hello 👋 
+21:18:31.323 { } [main] INFO  i.t.s.n.caller.CallerStarter - Operation state: SUCCEEDED 
+```

core/src/main/java/io/temporal/samples/nexusexternalcaller/caller/CallerStarter.java

@@ -0,0 +1,54 @@
+package io.temporal.samples.nexusexternalcaller.caller;
+
+import io.nexusrpc.OperationException;
+import io.nexusrpc.OperationStillRunningException;
+import io.nexusrpc.client.FetchOperationResultOptions;
+import io.nexusrpc.client.OperationHandle;
+import io.nexusrpc.client.ServiceClient;
+import io.nexusrpc.client.StartOperationResponse;
+import io.temporal.client.TemporalNexusServiceClientOptions;
+import io.temporal.client.WorkflowClient;
+import io.temporal.samples.nexus.options.ClientOptions;
+import io.temporal.samples.nexus.service.NexusService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.time.Duration;
+
+public class CallerStarter {
+  private static final Logger logger = LoggerFactory.getLogger(CallerStarter.class);
+
+  public static void main(String[] args) throws OperationStillRunningException, OperationException {
+    WorkflowClient client = ClientOptions.getWorkflowClient(args);
+
+    ServiceClient<NexusService> serviceClient =
+        client.newNexusServiceClient(
+            NexusService.class,
+            TemporalNexusServiceClientOptions.newBuilder()
+                .setEndpoint("my-nexus-endpoint-name")
+                .build());
+
+    // Execute a synchronous operation
+    NexusService.EchoOutput result =
+        serviceClient.executeOperation(NexusService::echo, new NexusService.EchoInput("Hello"));
+    logger.info("Execute echo operation: {}", result.getMessage());
+    // Start an asynchronous operation
+    StartOperationResponse<NexusService.HelloOutput> response =
+        serviceClient.startOperation(
+            NexusService::hello, new NexusService.HelloInput("Hello", NexusService.Language.EN));
+    if (!(response instanceof StartOperationResponse.Async)) {
+      throw new IllegalStateException("Expected an asynchronous operation response");
+    }
+    OperationHandle<NexusService.HelloOutput> handle =
+        ((StartOperationResponse.Async<NexusService.HelloOutput>) response).getHandle();
+    logger.info("Started hello operation with token: {}", handle.getOperationToken());
+    // Wait for the operation to complete
+    logger.info("Waiting for hello operation to complete...");
+    NexusService.HelloOutput helloResult =
+        handle.fetchResult(
+            FetchOperationResultOptions.newBuilder().setTimeout(Duration.ofSeconds(5)).build());
+    logger.info("Hello operation result: {}", helloResult.getMessage());
+    // We can also get the status of an operation
+    logger.info("Operation state: {}", handle.getInfo().getState());
+  }
+}

core/src/main/java/io/temporal/samples/nexusmultipleargs/handler/HandlerWorker.java → core/src/main/java/io/temporal/samples/nexusexternalcaller/handler/HandlerWorker.java

@@ -1,6 +1,8 @@
-package io.temporal.samples.nexusmultipleargs.handler;
+package io.temporal.samples.nexusexternalcaller.handler;
 
 import io.temporal.client.WorkflowClient;
+import io.temporal.samples.nexus.handler.HelloHandlerWorkflowImpl;
+import io.temporal.samples.nexus.handler.NexusServiceImpl;
 import io.temporal.samples.nexus.options.ClientOptions;
 import io.temporal.worker.Worker;
 import io.temporal.worker.WorkerFactory;