Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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. */ /* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.apache.samza.table.remote.couchbase; import com.couchbase.client.deps.io.netty.buffer.ByteBuf; import com.couchbase.client.deps.io.netty.util.ReferenceCountUtil; import com.couchbase.client.java.document.BinaryDocument; import com.couchbase.client.java.document.Document; import com.couchbase.client.java.document.JsonDocument; import com.couchbase.client.java.document.json.JsonObject; import com.google.common.base.Preconditions; import java.util.NoSuchElementException; import java.util.concurrent.CompletableFuture; import java.util.concurrent.TimeUnit; import org.apache.commons.lang3.StringUtils; import org.apache.samza.SamzaException; import org.apache.samza.context.Context; import org.apache.samza.table.remote.TableReadFunction; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import rx.Single; import rx.SingleSubscriber; /** * TableReadFunction implementation for reading from Couchbase. The value type can be either {@link JsonObject} or * any other Object. If the value type is JsonObject, data in JSON format will be read from Couchbase directly as * JsonObject. Otherwise, a {@link org.apache.samza.serializers.Serde} needs to be provided to serialize and * deserialize the value object. * @param <V> Type of values to read from Couchbase */ public class CouchbaseTableReadFunction<V> extends BaseCouchbaseTableFunction<V> implements TableReadFunction<String, V> { private static final Logger LOGGER = LoggerFactory.getLogger(CouchbaseTableReadFunction.class); protected final Class<? extends Document<?>> documentType; /** * Construct an instance of {@link CouchbaseTableReadFunction}. * @param bucketName Name of the couchbase bucket * @param clusterNodes Some Hosts of the Couchbase cluster. Recommended to provide more than one nodes so that if * the first node could not be connected, other nodes can be tried. * @param valueClass Type of values */ public CouchbaseTableReadFunction(String bucketName, Class<V> valueClass, String... clusterNodes) { super(bucketName, valueClass, clusterNodes); documentType = JsonObject.class.isAssignableFrom(valueClass) ? JsonDocument.class : BinaryDocument.class; } @Override public void init(Context context) { super.init(context); LOGGER.info("Read function for bucket {} initialized successfully", bucketName); } @Override public CompletableFuture<V> getAsync(String key) { Preconditions.checkArgument(StringUtils.isNotBlank(key), "key must not be null, empty or blank"); CompletableFuture<V> future = new CompletableFuture<>(); Single<? extends Document<?>> singleObservable = bucket.async() .get(key, documentType, timeout.toMillis(), TimeUnit.MILLISECONDS).toSingle(); singleObservable.subscribe(new SingleSubscriber<Document<?>>() { @Override public void onSuccess(Document<?> document) { if (document != null) { if (document instanceof BinaryDocument) { handleGetAsyncBinaryDocument((BinaryDocument) document, future, key); } else { // V is of type JsonObject future.complete((V) document.content()); } } else { // The Couchbase async client should not return null future.completeExceptionally( new SamzaException(String.format("Got unexpected null value from key %s", key))); } } @Override public void onError(Throwable throwable) { if (throwable instanceof NoSuchElementException) { // There is no element returned by the observable, meaning the key doesn't exist. future.complete(null); } else { future.completeExceptionally( new SamzaException(String.format("Failed to get key %s", key), throwable)); } } }); return future; } /** * Helper method to read bytes from binaryDocument and release the buffer. */ private void handleGetAsyncBinaryDocument(BinaryDocument binaryDocument, CompletableFuture<V> future, String key) { ByteBuf buffer = binaryDocument.content(); try { byte[] bytes; if (buffer.hasArray() && buffer.arrayOffset() == 0 && buffer.readableBytes() == buffer.array().length) { bytes = buffer.array(); } else { bytes = new byte[buffer.readableBytes()]; buffer.readBytes(bytes); } future.complete(valueSerde.fromBytes(bytes)); } catch (Exception e) { future.completeExceptionally(new SamzaException( String.format("Failed to deserialize value of key %s with given serde", key), e)); } finally { ReferenceCountUtil.release(buffer); } } }