Add retry handler example

Signed-off-by: Mason <theforbiddenai@gmail.com>

examples/src/main/java/io/dapr/examples/workflows/retryhandler/DemoRetryHandler.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2025 The Dapr Authors
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package io.dapr.examples.workflows.retryhandler;
+
+import io.dapr.workflows.WorkflowContext;
+import io.dapr.workflows.WorkflowTaskRetryContext;
+import io.dapr.workflows.WorkflowTaskRetryHandler;
+import org.slf4j.Logger;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.concurrent.TimeUnit;
+
+public class DemoRetryHandler implements WorkflowTaskRetryHandler {
+
+  @Override
+  public boolean handle(WorkflowTaskRetryContext retryContext) {
+    WorkflowContext workflowContext = retryContext.getWorkflowContext();
+    Logger logger = retryContext.getWorkflowContext().getLogger();
+    Object input = retryContext.getInput();
+    String taskName = retryContext.getTaskName();
+
+    if(taskName.equalsIgnoreCase(FailureActivity.class.getName())) {
+      logger.info("FailureActivity Input: {}", input);
+      Instant timestampInput = (Instant) input;
+      // Add a second to ensure, it is 100% passed the time to success
+      Instant timeToSuccess = timestampInput.plusSeconds(FailureActivity.TIME_TO_SUCCESS + 1);
+      long timeToWait = timestampInput.until(timeToSuccess, TimeUnit.SECONDS.toChronoUnit());
+
+      logger.info("Waiting {} seconds before retrying.", timeToWait);
+      workflowContext.createTimer(Duration.ofSeconds(timeToWait)).await();
+      logger.info("Send request to FailureActivity");
+    }
+
+    return true;
+  }
+}

examples/src/main/java/io/dapr/examples/workflows/retryhandler/DemoRetryHandlerClient.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2025 The Dapr Authors
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package io.dapr.examples.workflows.retryhandler;
+
+import io.dapr.workflows.client.DaprWorkflowClient;
+import io.dapr.workflows.client.WorkflowInstanceStatus;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.concurrent.TimeoutException;
+
+public class DemoRetryHandlerClient {
+  /**
+   * The main method to start the client.
+   *
+   * @param args Input arguments (unused).
+   * @throws InterruptedException If program has been interrupted.
+   */
+  public static void main(String[] args) {
+    try (DaprWorkflowClient client = new DaprWorkflowClient()) {
+      String instanceId = client.scheduleNewWorkflow(DemoRetryWorkflow.class);
+      System.out.printf("Started a new external-event workflow with instance ID: %s%n", instanceId);
+
+      // Block until the orchestration completes. Then print the final status, which includes the output.
+      WorkflowInstanceStatus workflowInstanceStatus = client.waitForInstanceCompletion(
+              instanceId,
+              Duration.ofSeconds(30),
+              true);
+
+      System.out.printf("workflow instance with ID: %s completed with result: %s%n", instanceId,
+              workflowInstanceStatus.readOutputAs(Instant.class));
+    } catch (TimeoutException | InterruptedException e) {
+      throw new RuntimeException(e);
+    }
+  }
+}

examples/src/main/java/io/dapr/examples/workflows/retryhandler/DemoRetryHandlerWorker.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2025 The Dapr Authors
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package io.dapr.examples.workflows.retryhandler;
+
+import io.dapr.workflows.runtime.WorkflowRuntime;
+import io.dapr.workflows.runtime.WorkflowRuntimeBuilder;
+
+public class DemoRetryHandlerWorker {
+  /**
+   * The main method of this app.
+   *
+   * @param args The port the app will listen on.
+   * @throws Exception An Exception.
+   */
+  public static void main(String[] args) throws Exception {
+    // Register the Workflow with the builder.
+    WorkflowRuntimeBuilder builder = new WorkflowRuntimeBuilder().registerWorkflow(DemoRetryWorkflow.class);
+    builder.registerActivity(FailureActivity.class);
+
+    // Build and then start the workflow runtime pulling and executing tasks
+    WorkflowRuntime runtime = builder.build();
+    System.out.println("Start workflow runtime");
+    runtime.start();
+  }
+}

examples/src/main/java/io/dapr/examples/workflows/retryhandler/DemoRetryWorkflow.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2025 The Dapr Authors
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package io.dapr.examples.workflows.retryhandler;
+
+import io.dapr.workflows.Workflow;
+import io.dapr.workflows.WorkflowStub;
+import io.dapr.workflows.WorkflowTaskOptions;
+import io.dapr.workflows.WorkflowTaskRetryHandler;
+import org.slf4j.Logger;
+
+import java.time.Instant;
+
+public class DemoRetryWorkflow implements Workflow {
+
+  @Override
+  public WorkflowStub create() {
+    return context -> {
+      Logger logger = context.getLogger();
+      logger.info("Starting RetryWorkflow: {}", context.getName());
+
+      WorkflowTaskRetryHandler retryHandler = new DemoRetryHandler();
+      WorkflowTaskOptions taskOptions = new WorkflowTaskOptions(retryHandler);
+
+      logger.info("RetryWorkflow is calling Activity: {}", FailureActivity.class.getName());
+      Instant currentTime = context.getCurrentInstant();
+      Instant result = context.callActivity(FailureActivity.class.getName(), currentTime, taskOptions, Instant.class).await();
+
+      logger.info("RetryWorkflow finished with: {}",  result);
+      context.complete(result);
+    };
+  }
+}

examples/src/main/java/io/dapr/examples/workflows/retryhandler/FailureActivity.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2025 The Dapr Authors
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package io.dapr.examples.workflows.retryhandler;
+
+import io.dapr.workflows.WorkflowActivity;
+import io.dapr.workflows.WorkflowActivityContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.time.Instant;
+
+public class FailureActivity implements WorkflowActivity {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(FailureActivity.class);
+  public static final long TIME_TO_SUCCESS = 10;
+
+  @Override
+  public Object run(WorkflowActivityContext ctx) {
+    LOGGER.info("Starting Activity: {}", ctx.getName());
+
+    Instant timestamp = ctx.getInput(Instant.class);
+
+    LOGGER.info("Input timestamp: {}", timestamp);
+    if(timestamp.plusSeconds(TIME_TO_SUCCESS).isBefore(Instant.now())) {
+      LOGGER.info("Completing Activity: {}", ctx.getName());
+      return Instant.now();
+    }
+
+    LOGGER.info("Throwing exception for Activity: {}", ctx.getName());
+
+    throw new RuntimeException("Failure!");
+  }
+}