Getting started with Java Java

Getting started with deepstreamHub is easy and takes less than ten minutes. However, if you have any questions, please get in touch.

This guide will show you how to build backend processes in Java using deepstreamHub's three core concepts: Records, Events and RPCs.

Create a free account and get your API key

Connect to deepstreamHub and log in

The first thing you'll need to do is set up a Java project with gradle and add the following line to your build.gradle file.

compile 'io.deepstream:deepstream.io-client-java:2.0.4'

From here we can instantiate a client as follows:

DeepstreamClient client = new DeepstreamClient("<Your app url here>");

and log in (we didn't configure any authentication, so there are no credentials required)

client.login();

Records (realtime datastore)

Creating a new record or retrieving an existent one is done using getRecord()

Record record = client.record.getRecord("test-record");

Values can be stored using the .set() method

// you can set the whole record
JsonObject data = new JsonObject();
data.addProperty("name", "Alex");
data.addProperty("favouriteDrink", "coffee");
record.set(data);

// or just a path
record.set( "hobbies", new String[]{ "sailing", "reading" });

and be retrieved using .get()

record.get(); // returns all record data as a JsonElement
record.get( "hobbies[1]" ); // returns the JsonElement 'reading'

subscribe to changes by you or other clients using .subscribe()

//subscribe to changes made by you or other clients using .subscribe()
record.subscribe(new RecordChangedCallback() {
    public void onRecordChanged(String recordName, JsonElement data) {
        // some value in the record has changed
    }
});

record.subscribe( "firstname", new RecordPathChangedCallback() {
    public void onRecordPathChanged(String recordName, String path, JsonElement data) {
        // the field "firstname" changed
    }
});

you can remove subscriptions with unsubscribe(), tell the server you're no longer interested in the record using .discard() or delete it using .delete().

Events (publish-subscribe)

Clients and backend processes can receive events using .subscribe()

client.event.subscribe("test-event", new EventListener() {
    public void onEvent(String eventName, Object data) {
        // do something with data
    }
});

... and publish events using .emit()

client.event.emit( "test-event", "some data");

RPCs (request-response)

You can make a request using .make()

JsonObject jsonObject = new JsonObject();
jsonObject.addProperty("a", 7);
jsonObject.addProperty("b", 8);
RpcResult rpcResult = client.rpc.make( "multiply-numbers", jsonObject);
int result = (Integer) rpcResult.getData(); // 56

and answer it using .provide()

client.rpc.provide("multiply-numbers", new RpcRequestedListener() {
    public void onRPCRequested(String name, Object data, RpcResponse response) {
        Gson gson = new Gson();
        JsonObject jsonData = (JsonObject) gson.toJsonTree(data);
        int a = jsonData.get("a").getAsInt();
        int b = jsonData.get("b").getAsInt();
        response.send(a * b);
    }
});

Where to go next?

Head over to the example app section to try some more concrete usecases.