com.pushtechnology.diffusion.examples.ControlClientUpdatingJSONTopicsWithCBOR Maven / Gradle / Ivy
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* Copyright (C) 2021, 2023 DiffusionData Ltd.
*
* 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
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*******************************************************************************/
package com.pushtechnology.diffusion.examples;
import static com.pushtechnology.diffusion.client.Diffusion.newTopicSpecification;
import static com.pushtechnology.diffusion.client.topics.details.TopicSpecification.REMOVAL;
import static java.util.Objects.requireNonNull;
import static java.util.concurrent.TimeUnit.SECONDS;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.cbor.CBORFactory;
import com.fasterxml.jackson.dataformat.cbor.CBORGenerator;
import com.pushtechnology.diffusion.client.Diffusion;
import com.pushtechnology.diffusion.client.features.TopicUpdate;
import com.pushtechnology.diffusion.client.features.control.topics.TopicControl;
import com.pushtechnology.diffusion.client.session.Session;
import com.pushtechnology.diffusion.client.topics.details.TopicSpecification;
import com.pushtechnology.diffusion.client.topics.details.TopicType;
import com.pushtechnology.diffusion.datatype.json.JSON;
import com.pushtechnology.diffusion.datatype.json.JSONDataType;
/**
* This example shows a control client creating a JSON topic and sending updates
* using a CBOR-format binary.
*
* There will be a topic for each currency for which rates are provided. The
* topic will be created under the FX topic - so, for example FX/GBP will
* contain a map of all rate conversions from the base GBP currency. The rates
* are represented as string decimal values (e.g. "12.457").
*
* Topic values are represented in JSON format e.g. {"USD":"123.45","HKD":"456.3"}.
*
* The {@code addRates} method shows how to create a new rates topic, specifying
* its initial map of values.
*
* The {@code changeRates} method which takes a map shows how to completely
* replace the set of rates for a currency with a new map of rates.
*
* After the first usage of changeRates for any topic the values is cached,
* and so subsequent set calls can compare with the last value
* and send only the differences to the server.
*
* @author DiffusionData Limited
* @since 6.8
* @see ClientConsumingJSONTopics
*/
public final class ControlClientUpdatingJSONTopicsWithCBOR {
private static final String ROOT_TOPIC = "FX";
private final Session session;
private final TopicControl topicControl;
private final TopicUpdate topicUpdate;
private final TopicSpecification topicSpecification;
private final CBORFactory cborFactory = new CBORFactory();
private final JSONDataType jsonDataType = Diffusion.dataTypes().json();
/**
* Constructor.
*
* @param serverUrl for example "ws://diffusion.example.com:80"
*/
public ControlClientUpdatingJSONTopicsWithCBOR(String serverUrl)
throws InterruptedException, ExecutionException, TimeoutException {
cborFactory.setCodec(new ObjectMapper());
session =
Diffusion.sessions().principal("control").password("password")
.open(serverUrl);
topicControl = session.feature(TopicControl.class);
topicUpdate = session.feature(TopicUpdate.class);
topicSpecification = newTopicSpecification(TopicType.JSON);
// Create the root topic that will remove itself when the session closes
final TopicSpecification specification =
topicSpecification
.withProperty(REMOVAL,
"When this session closes remove '?" + ROOT_TOPIC + "//'");
topicControl.addTopic(ROOT_TOPIC, specification).get(5, SECONDS);
}
/**
* Add a new rates topic and sets initial values.
*
* @param currency the base currency
* @param value the full map of initial rates values
* @throws IOException
* @throws UnsupportedOperationException
* @throws IllegalArgumentException
*/
public void addRates(
String currency, Map value)
throws IllegalArgumentException, UnsupportedOperationException, IOException {
topicUpdate
.addAndSet(rateTopicName(currency),
topicSpecification,
JSON.class,
mapToJSON(value));
}
/**
* Update an existing rates topic, replacing the rates mappings with a new
* set of mappings.
*
* @param currency the base currency
* @param values the new rates values
* @return a CompletableFuture that completes when a response is received
* from the server
* @throws IOException if unable to convert rates map
*/
public CompletableFuture changeRates(
String currency,
Map values) throws IOException {
return topicUpdate.set(
rateTopicName(currency),
JSON.class,
mapToJSON(values));
}
/**
* Convert a given map to a JSON object.
*/
private JSON mapToJSON(Map values) throws IOException {
// Use the third-party Jackson library to write out the values map as a
// CBOR-format binary.
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
final CBORGenerator generator = cborFactory.createGenerator(baos);
generator.writeObject(values);
return jsonDataType.readValue(baos.toByteArray());
}
/**
* Remove a rates entry (removes its topic).
*
* @param currency the currency
*
* @return a CompletableFuture that completes when a response is received
* from the server
*/
public CompletableFuture removeRates(String currency) {
final String topicName = rateTopicName(currency);
return topicControl.removeTopics(topicName);
}
/**
* Close the session.
*/
public void close() {
session.close();
}
/**
* Generate a hierarchical topic name for a rates topic.
*
* e.g. for currency=GBP would return "FX/GBP".
*
* @param currency the currency
* @return the topic name
*/
private static String rateTopicName(String currency) {
return String.format("%s/%s", ROOT_TOPIC, requireNonNull(currency));
}
}