Java

Pre-requisites

Importing Dapr’s Java SDK

For a Maven project, add the following to your pom.xml file:

  1. <project>
  2. ...
  3. <dependencies>
  4. ...
  5. // Dapr's core SDK with all features, except Actors.
  6. <dependency>
  7. <groupId>io.dapr</groupId>
  8. <artifactId>dapr-sdk</artifacetId>
  9. <version>1.1.0</version>
  10. </dependency>
  11. // Dapr's SDK for Actors (optional).
  12. <dependency>
  13. <groupId>io.dapr</groupId>
  14. <artifactId>dapr-sdk-actors</artifactId>
  15. <version>1.1.0</version>>
  16. </dependency>
  17. // Dapr's SDK integration with SpringBoot (optional).
  18. <dependency>
  19. <groupId>io.dapr</groupId>
  20. <artifactId>dapr-sdk-springboot</artifactId>
  21. <version>1.1.0</version>>
  22. </dependency>
  23. ...
  24. </dependencies>
  25. ...
  26. </project>

For a Gradle project, add the following to your build.gradle file:

  1. dependencies {
  2. ...
  3. // Dapr's core SDK with all features, except Actors.
  4. compile('io.dapr:dapr-sdk:1.1.0'))
  5. // Dapr's SDK for Actors (optional).
  6. compile('io.dapr:dapr-sdk-actors:1.1.0')
  7. // Dapr's SDK integration with SpringBoot (optional).
  8. compile('io.dapr:dapr-sdk-springboot:1.1.0')
  9. }

Building blocks

The Java SDK allows you to interface with all of the Dapr building blocks.

Invoke a service

  1. import io.dapr.client.DaprClient;
  2. import io.dapr.client.DaprClientBuilder;
  3. try (DaprClient client = (new DaprClientBuilder()).build()) {
  4. // invoke a 'GET' method (HTTP) skipping serialization: \say with a Mono<byte[]> return type
  5. // for gRPC set HttpExtension.NONE parameters below
  6. response = client.invokeMethod(SERVICE_TO_INVOKE, METHOD_TO_INVOKE, "{\"name\":\"World!\"}", HttpExtension.GET, byte[].class).block();
  7. // invoke a 'POST' method (HTTP) skipping serialization: to \say with a Mono<byte[]> return type
  8. response = client.invokeMethod(SERVICE_TO_INVOKE, METHOD_TO_INVOKE, "{\"id\":\"100\", \"FirstName\":\"Value\", \"LastName\":\"Value\"}", HttpExtension.POST, byte[].class).block();
  9. System.out.println(new String(response));
  10. // invoke a 'POST' method (HTTP) with serialization: \employees with a Mono<Employee> return type
  11. Employee newEmployee = new Employee("Nigel", "Guitarist");
  12. Employee employeeResponse = client.invokeMethod(SERVICE_TO_INVOKE, "employees", newEmployee, HttpExtension.POST, Employee.class).block();
  13. }

Save & get application state

  1. import io.dapr.client.DaprClient;
  2. import io.dapr.client.DaprClientBuilder;
  3. import io.dapr.client.domain.State;
  4. import reactor.core.publisher.Mono;
  5. try (DaprClient client = (new DaprClientBuilder()).build()) {
  6. // Save state
  7. client.saveState(STATE_STORE_NAME, FIRST_KEY_NAME, myClass).block();
  8. // Get state
  9. State<MyClass> retrievedMessage = client.getState(STATE_STORE_NAME, FIRST_KEY_NAME, MyClass.class).block();
  10. // Delete state
  11. client.deleteState(STATE_STORE_NAME, FIRST_KEY_NAME).block();
  12. }

Publish & subscribe to messages

Publish messages
  1. import io.dapr.client.DaprClient;
  2. import io.dapr.client.DaprClientBuilder;
  3. import io.dapr.client.domain.Metadata;
  4. import static java.util.Collections.singletonMap;
  5. try (DaprClient client = (new DaprClientBuilder()).build()) {
  6. client.publishEvent(PUBSUB_NAME, TOPIC_NAME, message, singletonMap(Metadata.TTL_IN_SECONDS, MESSAGE_TTL_IN_SECONDS)).block();
  7. }
Subscribe to messages
  1. import com.fasterxml.jackson.databind.ObjectMapper;
  2. import io.dapr.Topic;
  3. import io.dapr.client.domain.CloudEvent;
  4. import org.springframework.web.bind.annotation.PostMapping;
  5. import org.springframework.web.bind.annotation.RequestBody;
  6. import org.springframework.web.bind.annotation.RestController;
  7. import reactor.core.publisher.Mono;
  8. @RestController
  9. public class SubscriberController {
  10. private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
  11. @Topic(name = "testingtopic", pubsubName = "${myAppProperty:messagebus}")
  12. @PostMapping(path = "/testingtopic")
  13. public Mono<Void> handleMessage(@RequestBody(required = false) CloudEvent cloudEvent) {
  14. return Mono.fromRunnable(() -> {
  15. try {
  16. System.out.println("Subscriber got: " + cloudEvent.getData());
  17. System.out.println("Subscriber got: " + OBJECT_MAPPER.writeValueAsString(cloudEvent));
  18. } catch (Exception e) {
  19. throw new RuntimeException(e);
  20. }
  21. });
  22. }
  23. }

Interact with output bindings

  1. import io.dapr.client.DaprClient;
  2. import io.dapr.client.DaprClientBuilder;
  3. try (DaprClient client = (new DaprClientBuilder()).build()) {
  4. // sending a class with message; BINDING_OPERATION="create"
  5. client.invokeBinding(BINDING_NAME, BINDING_OPERATION, myClass).block();
  6. // sending a plain string
  7. client.invokeBinding(BINDING_NAME, BINDING_OPERATION, message).block();
  8. }

Retrieve secrets

  1. import com.fasterxml.jackson.databind.ObjectMapper;
  2. import io.dapr.client.DaprClient;
  3. import io.dapr.client.DaprClientBuilder;
  4. import java.util.Map;
  5. try (DaprClient client = (new DaprClientBuilder()).build()) {
  6. Map<String, String> secret = client.getSecret(SECRET_STORE_NAME, secretKey).block();
  7. System.out.println(JSON_SERIALIZER.writeValueAsString(secret));
  8. }

Actors

An actor is an isolated, independent unit of compute and state with single-threaded execution. Dapr provides an actor implementation based on the Virtual Actor pattern, which provides a single-threaded programming model and where actors are garbage collected when not in use. With Dapr’s implementaiton, you write your Dapr actors according to the Actor model, and Dapr leverages the scalability and reliability that the underlying platform provides.

  1. import io.dapr.actors.ActorMethod;
  2. import io.dapr.actors.ActorType;
  3. import reactor.core.publisher.Mono;
  4. @ActorType(name = "DemoActor")
  5. public interface DemoActor {
  6. void registerReminder();
  7. @ActorMethod(name = "echo_message")
  8. String say(String something);
  9. void clock(String message);
  10. @ActorMethod(returns = Integer.class)
  11. Mono<Integer> incrementAndGet(int delta);
  12. }