Java tutorial
/* * * Copyright 2016 Netflix, Inc. * * 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 com.netflix.hollow.example.consumer.infrastructure; import com.amazonaws.auth.AWSCredentials; import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient; import com.amazonaws.services.dynamodbv2.document.DynamoDB; import com.amazonaws.services.dynamodbv2.document.Item; import com.amazonaws.services.dynamodbv2.document.Table; import com.netflix.hollow.api.client.HollowAnnouncementWatcher; public class DynamoDBAnnouncementWatcher extends HollowAnnouncementWatcher { private final DynamoDB dynamoDB; private final String tableName; private final String blobNamespace; private long latestVersion; public DynamoDBAnnouncementWatcher(AWSCredentials credentials, String tableName, String blobNamespace) { this.dynamoDB = new DynamoDB(new AmazonDynamoDBClient(credentials)); this.tableName = tableName; this.blobNamespace = blobNamespace; this.latestVersion = readLatestVersion(); } @Override public long getLatestVersion() { return latestVersion; } @Override public void subscribeToEvents() { Thread t = new Thread(new Runnable() { public void run() { while (true) { try { long currentVersion = readLatestVersion(); if (latestVersion != currentVersion) { latestVersion = currentVersion; triggerAsyncRefresh(); } Thread.sleep(1000); } catch (Throwable th) { th.printStackTrace(); } } } }); t.setDaemon(true); t.start(); } public long readLatestVersion() { Table table = dynamoDB.getTable(tableName); Item item = table.getItem("namespace", blobNamespace, "version, pin_version", null); if (item.isPresent("pin_version") && !item.isNull("pin_version")) return item.getLong("pin_version"); return item.getLong("version"); } }