| /* |
| * 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.beam.sdk.transforms; |
| |
| import org.apache.beam.sdk.values.KV; |
| import org.apache.beam.sdk.values.PCollection; |
| import org.apache.beam.vendor.guava.v20_0.com.google.common.base.Joiner; |
| |
| /** |
| * {@link PTransform PTransforms} for converting a {@link PCollection PCollection<?>}, {@link |
| * PCollection PCollection<KV<?,?>>}, or {@link PCollection |
| * PCollection<Iterable<?>>} to a {@link PCollection PCollection<String>}. |
| * |
| * <p><b>Note</b>: For any custom string conversion and formatting, we recommend applying your own |
| * {@link ProcessFunction} using {@link MapElements#via(ProcessFunction)} |
| */ |
| public final class ToString { |
| private ToString() { |
| // do not instantiate |
| } |
| |
| /** |
| * Transforms each element of the input {@link PCollection} to a {@link String} using the {@link |
| * Object#toString} method. |
| */ |
| public static PTransform<PCollection<?>, PCollection<String>> elements() { |
| return new Elements(); |
| } |
| |
| /** |
| * Transforms each element of the input {@link PCollection} to a {@link String} by using the |
| * {@link Object#toString} on the key followed by a "," followed by the {@link Object#toString} of |
| * the value. |
| */ |
| public static PTransform<PCollection<? extends KV<?, ?>>, PCollection<String>> kvs() { |
| return kvs(","); |
| } |
| |
| /** |
| * Transforms each element of the input {@link PCollection} to a {@link String} by using the |
| * {@link Object#toString} on the key followed by the specified delimiter followed by the {@link |
| * Object#toString} of the value. |
| * |
| * @param delimiter The delimiter to put between the key and value |
| */ |
| public static PTransform<PCollection<? extends KV<?, ?>>, PCollection<String>> kvs( |
| String delimiter) { |
| return new KVs(delimiter); |
| } |
| |
| /** |
| * Transforms each item in the iterable of the input {@link PCollection} to a {@link String} using |
| * the {@link Object#toString} method followed by a "," until the last element in the iterable. |
| * There is no trailing delimiter. |
| */ |
| public static PTransform<PCollection<? extends Iterable<?>>, PCollection<String>> iterables() { |
| return iterables(","); |
| } |
| |
| /** |
| * Transforms each item in the iterable of the input {@link PCollection} to a {@link String} using |
| * the {@link Object#toString} method followed by the specified delimiter until the last element |
| * in the iterable. There is no trailing delimiter. |
| * |
| * @param delimiter The delimiter to put between the items in the iterable. |
| */ |
| public static PTransform<PCollection<? extends Iterable<?>>, PCollection<String>> iterables( |
| String delimiter) { |
| return new Iterables(delimiter); |
| } |
| |
| /** |
| * A {@link PTransform} that converts a {@code PCollection} to a {@code PCollection<String>} using |
| * the {@link Object#toString} method. |
| * |
| * <p>Example of use: |
| * |
| * <pre>{@code |
| * PCollection<Long> longs = ...; |
| * PCollection<String> strings = longs.apply(ToString.elements()); |
| * }</pre> |
| * |
| * <p><b>Note</b>: For any custom string conversion and formatting, we recommend applying your own |
| * {@link ProcessFunction} using {@link MapElements#via(ProcessFunction)} |
| */ |
| private static final class Elements extends PTransform<PCollection<?>, PCollection<String>> { |
| @Override |
| public PCollection<String> expand(PCollection<?> input) { |
| return input.apply( |
| MapElements.via( |
| new SimpleFunction<Object, String>() { |
| @Override |
| public String apply(Object input) { |
| return input.toString(); |
| } |
| })); |
| } |
| } |
| |
| /** |
| * A {@link PTransform} that converts a {@code PCollection} of {@code KV} to a {@code |
| * PCollection<String>} using the {@link Object#toString} method for the key and value and an |
| * optional delimiter. |
| * |
| * <p>Example of use: |
| * |
| * <pre>{@code |
| * PCollection<KV<String, Long>> nameToLong = ...; |
| * PCollection<String> strings = nameToLong.apply(ToString.kv()); |
| * }</pre> |
| * |
| * <p><b>Note</b>: For any custom string conversion and formatting, we recommend applying your own |
| * {@link ProcessFunction} using {@link MapElements#via(ProcessFunction)} |
| */ |
| private static final class KVs |
| extends PTransform<PCollection<? extends KV<?, ?>>, PCollection<String>> { |
| private final String delimiter; |
| |
| public KVs(String delimiter) { |
| this.delimiter = delimiter; |
| } |
| |
| @Override |
| public PCollection<String> expand(PCollection<? extends KV<?, ?>> input) { |
| return input.apply( |
| MapElements.via( |
| new SimpleFunction<KV<?, ?>, String>() { |
| @Override |
| public String apply(KV<?, ?> input) { |
| return input.getKey().toString() + delimiter + input.getValue().toString(); |
| } |
| })); |
| } |
| } |
| |
| /** |
| * A {@link PTransform} that converts a {@code PCollection} of {@link Iterable} to a {@code |
| * PCollection<String>} using the {@link Object#toString} method and an optional delimiter. |
| * |
| * <p>Example of use: |
| * |
| * <pre>{@code |
| * PCollection<Iterable<Long>> longs = ...; |
| * PCollection<String> strings = nameToLong.apply(ToString.iterable()); |
| * }</pre> |
| * |
| * <p><b>Note</b>: For any custom string conversion and formatting, we recommend applying your own |
| * {@link ProcessFunction} using {@link MapElements#via(ProcessFunction)} |
| */ |
| private static final class Iterables |
| extends PTransform<PCollection<? extends Iterable<?>>, PCollection<String>> { |
| private final String delimiter; |
| |
| public Iterables(String delimiter) { |
| this.delimiter = delimiter; |
| } |
| |
| @Override |
| public PCollection<String> expand(PCollection<? extends Iterable<?>> input) { |
| return input.apply( |
| MapElements.via( |
| new SimpleFunction<Iterable<?>, String>() { |
| @Override |
| public String apply(Iterable<?> input) { |
| return Joiner.on(delimiter).join(input); |
| } |
| })); |
| } |
| } |
| } |