State management sample

This sample illustrates the capabilities provided by Dapr Java SDK for querying states. For further information about querying saved state please refer to this link

Pre-requisites

• Dapr CLI.
• Java JDK 11 (or greater):
  • Microsoft JDK 11
  • Oracle JDK 11
  • OpenJDK 11
• Apache Maven version 3.x.

Checking out the code

Clone this repository:

git clone https://github.com/dapr/java-sdk.git
cd java-sdk

Then build the Maven project:

# make sure you are in the `java-sdk` directory.
mvn install

Then change into the examples directory:

cd examples

Initialize Dapr

Run dapr init to initialize Dapr in Self-Hosted Mode if it's not already initialized.

Run MongoDB

docker compose -f ./src/main/java/io/dapr/examples/querystate/docker-compose-single-mongo.yml up -d

Running the State Client

This example uses the Java SDK Dapr client in order to save bulk state and query state, in this case, an instance of a class. See the code snippets below:

The class saved and queried for is as below:

public class Listing {

  @JsonProperty
  private String propertyType;

  @JsonProperty
  private String id;

  @JsonProperty
  private String city;

  @JsonProperty
  private String state;

  public Listing() {
  }

  public String getPropertyType() {
    return propertyType;
  }

  public void setPropertyType(String propertyType) {
    this.propertyType = propertyType;
  }

  public String getId() {
    return id;
  }

  public void setId(String id) {
    this.id = id;
  }

  public String getCity() {
    return city;
  }

  public void setCity(String city) {
    this.city = city;
  }

  public String getState() {
    return state;
  }

  public void setState(String state) {
    this.state = state;
  }

  @Override
  public String toString() {
    return "Listing{"
        + "propertyType='" + propertyType + '\''
        + ", id=" + id
        + ", city='" + city + '\''
        + ", state='" + state + '\''
        + '}';
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    Listing listing = (Listing) o;
    return id == listing.id
        && propertyType.equals(listing.propertyType)
        && Objects.equals(city, listing.city)
        && Objects.equals(state, listing.state);
  }

  @Override
  public int hashCode() {
    return Objects.hash(propertyType, id, city, state);
  }
}

The main application class for the example is as follows:

public class QuerySavedState {

  public static class MyData {
    ///...
  }

  private static final String STATE_STORE_NAME = "querystatestore";

  private static final String FIRST_KEY_NAME = "key1";

  private static final String SECOND_KEY_NAME = "key2";

  private static final String THIRD_KEY_NAME = "key3";

  /**
   * Executes the state actions.
   * @param args messages to be sent as state value.
   */
  public static void main(String[] args) throws Exception {
    DaprClientBuilder builder = new DaprClientBuilder();
    try (DaprClient client = builder.build(); DaprPreviewClient previewClient = builder.buildPreviewClient()) {
      System.out.println("Waiting for Dapr sidecar ...");
      client.waitForSidecar(10000).block();
      System.out.println("Dapr sidecar is ready.");

      Listing first = new Listing();
      first.setPropertyType("apartment");
      first.setId("1000");
      first.setCity("Seattle");
      first.setState("WA");
      Listing second = new Listing();
      second.setPropertyType("row-house");
      second.setId("1002");
      second.setCity("Seattle");
      second.setState("WA");
      Listing third = new Listing();
      third.setPropertyType("apartment");
      third.setId("1003");
      third.setCity("Portland");
      third.setState("OR");
      Listing fourth = new Listing();
      fourth.setPropertyType("apartment");
      fourth.setId("1001");
      fourth.setCity("Portland");
      fourth.setState("OR");
      Map<String, String> meta = new HashMap<>();
      meta.put("contentType", "application/json");

      SaveStateRequest request = new SaveStateRequest(STATE_STORE_NAME).setStates(
          new State<>("1", first, null, meta, null),
          new State<>("2", second, null, meta, null),
          new State<>("3", third, null, meta, null),
          new State<>("4", fourth, null, meta, null)
      );
      client.saveBulkState(request).block();

      System.out.println("Insert key: 1" + ", data: " + first);
      System.out.println("Insert key: 2" + ", data: " + second);
      System.out.println("Insert key: 3" + ", data: " + third);
      System.out.println("Insert key: 4" + ", data: " + fourth);


      Query query = new Query()
          .setFilter(new EqFilter<>("propertyType", "apartment"))
          .setSort(Arrays.asList(new Sorting("id", Sorting.Order.DESC)));

      QueryStateRequest queryStateRequest = new QueryStateRequest(STATE_STORE_NAME)
          .setQuery(query);

      QueryStateResponse<Listing> result = previewClient.queryState(queryStateRequest, Listing.class).block();

      System.out.println("Found " + result.getResults().size() + " items.");
      for (QueryStateItem<Listing> item : result.getResults()) {
        System.out.println("Key: " + item.getKey());
        System.out.println("Data: " + item.getValue());
      }

      // This is an example, so for simplicity we are just exiting here.
      // Normally a dapr app would be a web service and not exit main.
      System.out.println("Done");
      System.exit(0);
    }
  }
}

The code uses the DaprClient created by the DaprClientBuilder for waiting for the sidecar to start as well as to save state. Notice that this builder uses default settings. Internally, it is using DefaultObjectSerializer for two properties: objectSerializer is for Dapr's sent and received objects, and stateSerializer is for objects to be persisted.

The code uses the DaprPreviewClient created by the DaprClientBuilder which is used for the queryState preview API.

This example performs multiple operations:

• client.waitForSidecar(...) for waiting until Dapr's sidecar is ready.
• client.saveBulkState(...) for persisting an instance of Listing.
• client.query(...) operation in order to query for persisted state.

The Dapr clients are also within a try-with-resource block to properly close the clients at the end.

Running the example

Run this example with the following command:

dapr run --resources-path ./components/state --app-id query-state-example -H 3600 -- java -Ddapr.api.protocol=HTTP -jar target/dapr-java-sdk-examples-exec.jar io.dapr.examples.querystate.QuerySavedState

Once running, the QuerySaveState example should print the output as follows:

== APP == Waiting for Dapr sidecar ...
== APP == Dapr sidecar is ready.
== APP == Insert key: 1, data: Listing{propertyType='apartment', id=1000, city='Seattle', state='WA'}
== APP == Insert key: 2, data: Listing{propertyType='row-house', id=1002, city='Seattle', state='WA'}
== APP == Insert key: 3, data: Listing{propertyType='apartment', id=1003, city='Portland', state='OR'}
== APP == Insert key: 4, data: Listing{propertyType='apartment', id=1001, city='Portland', state='OR'}
== APP == Found 3 items.
== APP == Key: 3
== APP == Data: Listing{propertyType='apartment', id=1003, city='Portland', state='OR'}
== APP == Key: 4
== APP == Data: Listing{propertyType='apartment', id=1001, city='Portland', state='OR'}
== APP == Key: 1
== APP == Data: Listing{propertyType='apartment', id=1000, city='Seattle', state='WA'}
== APP == Done

Note that the output is in descending order of the field id, and all the propertyType field values are the same apartment.

Cleanup

To close the app either press CTRL+C or run

dapr stop --app-id query-state-example

Then, stop MongoDB container.

docker compose -f ./src/main/java/io/dapr/examples/querystate/docker-compose-single-mongo.yml down