adding fanoutfanin example

Author: salaboy

tutorials/workflow/java/fan-out-fan-in/README.md

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+# Fan-out/Fan-in
+
+This tutorial demonstrates how to author a workflow where multiple independent tasks can be scheduled and executed simultaneously. The workflow can either wait until all tasks are completed to proceed, or continue when the fastest task is completed. For more information about the fan-out/fan-in pattern see the [Dapr docs](https://docs.dapr.io/developing-applications/building-blocks/workflow/workflow-patterns/#fan-outfan-in).
+
+## Inspect the code
+
+Open the [`FanOutFanInWorkflow.java`](src/main/java/io/dapr/springboot/examples/fanoutfanin/FanOutFanInWorkflow.java) file in the `tutorials/workflow/java/fan-out-fan-in/src/main/java/io/dapr/springboot/examples/fanoutfanin` folder. This file contains the definition for the workflow.
+
+```mermaid
+graph LR
+   SW((Start
+   Workflow))
+   subgraph for each word in the input
+    GWL[GetWordLength]
+   end
+   SHORT[Select the
+   shortest word]
+   ALL[Wait until all tasks
+   are completed]
+   EW((End
+   Workflow))
+   SW --> GWL
+   GWL --> ALL
+   ALL --> SHORT
+   SHORT --> EW
+```
+
+## Run the tutorial
+
+1. Use a terminal to navigate to the `tutorials/workflow/java/task-chaining` folder.
+2. Build and run the project using Maven.
+
+    ```bash
+    mvn spring-boot:test-run
+    ```
+
+3. Use the POST request in the [`fanoutfanin.http`](./fanoutfanin.http) file to start the workflow, or use this cURL command:
+
+    ```bash
+    curl -i --request POST \
+    --url http://localhost:8080/start \
+    --header 'content-type: application/json' \
+    --data '["which","word","is","the","shortest"]'
+    ```
+
+    The input for the workflow is an array of strings:
+
+    ```json
+    [
+        "which",
+        "word",
+        "is",
+        "the",
+        "shortest"
+    ]
+    ```
+
+    The expected app logs are as follows:
+
+    ```text
+    == APP - fanoutfanin == GetWordLength: Received input: word.
+    == APP - fanoutfanin == GetWordLength: Received input: is.
+    == APP - fanoutfanin == GetWordLength: Received input: the.
+    == APP - fanoutfanin == GetWordLength: Received input: shortest.
+    == APP - fanoutfanin == GetWordLength: Received input: which.
+    ```
+
+    > Note that the order of the logs may vary.
+
+4. Use the GET request in the [`fanoutfanin.http`](./fanoutfanin.http) file to get the status of the workflow, or use this cURL command:
+
+    ```bash
+    curl --request GET --url http://localhost:8080/output
+    ```
+
+5. The expected serialized output of the workflow is an array with two strings:
+
+    ```txt
+    "["is"]"
+    ```
+
+6. Stop the application by pressing `Ctrl+C`.

tutorials/workflow/java/fan-out-fan-in/fanoutfanin

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+@apphost=http://localhost:8080
+
+### Start the FanOutFanIn workflow
+# @name startWorkflowRequest
+POST {{ apphost }}/start
+
+### Get the workflow status
+GET {{ apphost }}/output

tutorials/workflow/java/fan-out-fan-in/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>org.springframework.boot</groupId>
+    <artifactId>spring-boot-starter-parent</artifactId>
+    <version>3.4.5</version>
+    <relativePath/> <!-- lookup parent from repository -->
+  </parent>
+
+  <artifactId>fan-out-fan-in</artifactId>
+  <name>fan-out-fan-in</name>
+  <description>Fan Out/In Workflow Example</description>
+
+  <properties>
+    <dapr.spring.version>0.15.0-rc-7</dapr.spring.version>
+  </properties>
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-web</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-test</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>io.dapr.spring</groupId>
+      <artifactId>dapr-spring-boot-starter</artifactId>
+      <version>${dapr.spring.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.dapr.spring</groupId>
+      <artifactId>dapr-spring-boot-starter-test</artifactId>
+      <version>${dapr.spring.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>io.rest-assured</groupId>
+      <artifactId>rest-assured</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+      </plugin>
+    </plugins>
+  </build>
+</project>

tutorials/workflow/java/fan-out-fan-in/src/main/java/io/dapr/springboot/examples/FanOutFanInApplication.java

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+/*
+ * 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.springboot.examples;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+
+@SpringBootApplication
+public class FanOutFanInApplication {
+
+  public static void main(String[] args) {
+    SpringApplication.run(FanOutFanInApplication.class, args);
+  }
+
+}

tutorials/workflow/java/fan-out-fan-in/src/main/java/io/dapr/springboot/examples/FanOutFanInConfiguration.java

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+/*
+ * 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.springboot.examples;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.client.RestTemplate;
+
+@Configuration
+public class FanOutFanInConfiguration {
+
+  @Bean
+  public RestTemplate restTemplate() {
+    return new RestTemplateBuilder().build();
+  }
+
+  @Bean
+  public ObjectMapper mapper() {
+    return new ObjectMapper();
+  }
+}

tutorials/workflow/java/fan-out-fan-in/src/main/java/io/dapr/springboot/examples/FanOutFanInRestController.java

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+/*
+ * 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.springboot.examples;
+
+
+import io.dapr.spring.workflows.config.EnableDaprWorkflows;
+import io.dapr.springboot.examples.fanoutfanin.FanOutFanInWorkflow;
+import io.dapr.workflows.client.DaprWorkflowClient;
+import io.dapr.workflows.client.WorkflowInstanceStatus;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+import java.util.concurrent.TimeoutException;
+
+@RestController
+@EnableDaprWorkflows
+public class FanOutFanInRestController {
+
+  private final Logger logger = LoggerFactory.getLogger(FanOutFanInRestController.class);
+
+  @Autowired
+  private DaprWorkflowClient daprWorkflowClient;
+
+  /*
+   * **Note:** This local variable is used for examples purposes only.
+   * For production scenarios, you will need to map workflowInstanceIds to your business scenarios.
+   */
+  private String instanceId;
+
+  /**
+   * Run Fan Out / Fan In Demo Workflow
+   *
+   * @return the instanceId of the FanOutFanInWorkflow execution
+   */
+  @PostMapping("start")
+  public String fanoutfanin(@RequestBody List<String> input) {
+    instanceId = daprWorkflowClient.scheduleNewWorkflow(FanOutFanInWorkflow.class, input);
+    return instanceId;
+  }
+
+  /**
+   * Obtain the output of the workflow
+   *
+   * @return the output of the FanOutFanInWorkflow execution
+   */
+  @GetMapping("output")
+  public String output() throws TimeoutException {
+    WorkflowInstanceStatus instanceState = daprWorkflowClient.getInstanceState(instanceId, true);
+    if (instanceState != null) {
+      return instanceState.readOutputAs(String.class);
+    }
+    return "N/A";
+  }
+
+
+}

tutorials/workflow/java/fan-out-fan-in/src/main/java/io/dapr/springboot/examples/fanoutfanin/FanOutFanInWorkflow.java

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+/*
+ * Copyright 2023 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.springboot.examples.fanoutfanin;
+
+import io.dapr.durabletask.Task;
+import io.dapr.workflows.Workflow;
+import io.dapr.workflows.WorkflowStub;
+import org.springframework.stereotype.Component;
+
+import java.io.Serializable;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+
+@Component
+public class FanOutFanInWorkflow implements Workflow {
+  @Override
+  public WorkflowStub create() {
+    return ctx -> {
+        ctx.getLogger().info("Starting Workflow: {}", ctx.getName());
+
+        List<String> inputs = ctx.getInput(List.class);
+        if (inputs.isEmpty()) {
+          throw new IllegalStateException("Input cannot be empty.");
+        }
+        // This list will contain the tasks that will be executed by the Dapr Workflow engine.
+        List<Task<WordLength>> tasks = inputs.stream()
+                .map(input -> ctx.callActivity(GetWordLengthActivity.class.getName(), input,
+                        WordLength.class))
+                .collect(Collectors.toList());
+
+        // The Dapr Workflow engine will schedule all the tasks and wait for all tasks to complete before continuing.
+        List<WordLength> allWordLengths = ctx.allOf(tasks).await();
+        //Let's sort the list of WordLengths
+        allWordLengths.sort(Comparator.comparingInt(WordLength::length));
+        //Pick the first one
+        String shortestWord = allWordLengths.get(0).word();
+
+        ctx.complete(shortestWord);
+    };
+  }
+  record WordLength(String word, int length) implements Serializable {}
+}

tutorials/workflow/java/fan-out-fan-in/src/main/java/io/dapr/springboot/examples/fanoutfanin/GetWordLengthActivity.java

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+/*
+ * Copyright 2023 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.springboot.examples.fanoutfanin;
+
+import io.dapr.workflows.WorkflowActivity;
+import io.dapr.workflows.WorkflowActivityContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Component;
+
+@Component
+public class GetWordLengthActivity implements WorkflowActivity {
+
+  @Override
+  public Object run(WorkflowActivityContext ctx) {
+    Logger logger = LoggerFactory.getLogger(GetWordLengthActivity.class);
+    var input = ctx.getInput(String.class);
+    logger.info("{} : Received input: {}", ctx.getName(), input);
+    return new FanOutFanInWorkflow.WordLength(input, input.length());
+  }
+
+
+}

tutorials/workflow/java/fan-out-fan-in/src/main/resources/application.properties

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+spring.application.name=fan-out-fan-in