ahmedabu98 commented on code in PR #32367: URL: https://github.com/apache/beam/pull/32367#discussion_r1765609012
########## sdks/java/core/src/main/java/org/apache/beam/sdk/util/RowStringInterpolator.java: ########## @@ -0,0 +1,192 @@ +/* + * 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.util; + +import java.io.Serializable; +import java.util.HashSet; +import java.util.List; +import java.util.Set; +import java.util.regex.Matcher; +import java.util.regex.Pattern; +import java.util.stream.Collectors; +import org.apache.beam.sdk.schemas.Schema; +import org.apache.beam.sdk.transforms.windowing.BoundedWindow; +import org.apache.beam.sdk.transforms.windowing.PaneInfo; +import org.apache.beam.sdk.values.Row; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.MoreObjects; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Splitter; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Sets; +import org.apache.commons.lang3.StringUtils; +import org.checkerframework.checker.nullness.qual.Nullable; +import org.joda.time.Instant; + +/** + * A utility that interpolates values in a pre-determined {@link String} using an input Beam {@link + * Row}. + * + * <p>The {@link RowStringInterpolator} looks for field names specified inside {curly braces}. For + * example, if the interpolator is configured with the String {@code "unified {foo} and streaming"}, + * it will look for a field name {@code "foo"} in the input {@link Row} and substitute in that + * value. If a {@link RowStringInterpolator} is configured with a template String that contains no + * placeholders (i.e. no curly braces), it will simply return that String, untouched. + * + * <p>Nested fields can be specified using dot-notation (e.g. {@code "top.middle.nested"}). + * + * <p>Configure a {@link RowStringInterpolator} like so: + * + * <pre>{@code + * String template = "unified {foo} and {bar.baz}!"; + * Row inputRow = {foo: "batch", bar: {baz: "streaming"}, ...}; + * + * RowStringInterpolator interpolator = new RowStringInterpolator(template, beamSchema); + * String output = interpolator.interpolate(inputRow); + * // output --> "unified batch and streaming!" + * }</pre> + * + * <p>Additionally, {@link #interpolate(Row, BoundedWindow, PaneInfo, Instant)} can be used in + * streaming scenarios to substitute windowing metadata into the template String. To make use of + * this, use the relevant placeholder: + * + * <ul> + * <li>$WINDOW: the window's string representation + * <li>$PANE_INDEX: the pane's index + * <li>$YYYY: the element timestamp's year + * <li>$MM: the element timestamp's month + * <li>$DD: the element timestamp's day + * </ul> + * + * <p>For example, your Sting template can look like: + * + * <pre>{@code "unified {foo} and {bar} since {$YYYY}-{$MM}!"}</pre> + */ +public class RowStringInterpolator implements Serializable { + private final String template; + private final Set<String> fieldsToReplace; + // Represents the string representation of the element's window + public static final String WINDOW = "$WINDOW"; + public static final String PANE_INDEX = "$PANE_INDEX"; + // Represents the element's pane index + public static final String YYYY = "$YYYY"; + public static final String MM = "$MM"; + public static final String DD = "$DD"; + private static final Set<String> WINDOWING_METADATA = + Sets.newHashSet(WINDOW, PANE_INDEX, YYYY, MM, DD); + private static final Pattern TEMPLATE_PATTERN = Pattern.compile("\\{(.+?)}"); + + /** + * @param template a String template, potentially with placeholders in the form of curly braces, + * e.g. {@code "my {foo} template"}. During interpolation, these placeholders are replaced + * with values in the Beam Row. For more details and examples, refer to the top-level + * documentation. + * @param rowSchema {@link Row}s used for interpolation are expected to be compatible with this + * {@link Schema}. + */ + public RowStringInterpolator(String template, Schema rowSchema) { + this.template = template; + + Matcher m = TEMPLATE_PATTERN.matcher(template); + fieldsToReplace = new HashSet<>(); + while (m.find()) { + fieldsToReplace.add(StringUtils.strip(m.group(), "{}")); + } + + List<String> rowFields = + fieldsToReplace.stream() + .filter(f -> !WINDOWING_METADATA.contains(f)) + .collect(Collectors.toList()); + + RowFilter.validateSchemaContainsFields(rowSchema, rowFields, "string interpolation"); + } + + /** Performs string interpolation on the template using values from the input {@link Row}. */ + public String interpolate(Row row) { Review Comment: Figured why not, but on a second thought will remove it to keep windowing properties as first-class citizens -- This is an automated message from the Apache Git Service. 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