C0urante commented on code in PR #15379: URL: https://github.com/apache/kafka/pull/15379#discussion_r1570939313
########## connect/transforms/src/main/java/org/apache/kafka/connect/transforms/field/SingleFieldPath.java: ########## @@ -0,0 +1,258 @@ +/* + * 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.kafka.connect.transforms.field; + +import org.apache.kafka.common.config.ConfigException; +import org.apache.kafka.connect.data.Field; +import org.apache.kafka.connect.data.Schema; +import org.apache.kafka.connect.data.Struct; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.Map; +import java.util.Objects; + +/** + * A SingleFieldPath is composed of one or more field names, known as path steps, + * to access values within a data object (either {@code Struct} or {@code Map<String, Object>}). + * + * <p>If the SMT requires accessing multiple fields on the same data object, use {@link MultiFieldPaths} instead. + * + * <p>The field path semantics are defined by the {@link FieldSyntaxVersion syntax version}. + * + * @see <a href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-821%3A+Connect+Transforms+support+for+nested+structures";>KIP-821</a> + * @see FieldSyntaxVersion + * @see MultiFieldPaths + */ +public class SingleFieldPath { + // Invariants: + // - A field path can contain one or more steps + private static final char BACKTICK = '`'; + private static final char DOT = '.'; + private static final char BACKSLASH = '\\'; + + private final String originalPath; + private final FieldSyntaxVersion version; + private final List<String> steps; + + public SingleFieldPath(String pathText, FieldSyntaxVersion version) { + this.originalPath = Objects.requireNonNull(pathText, "Field path cannot be null"); + this.version = version; + switch (version) { + case V1: // backward compatibility + this.steps = Collections.singletonList(pathText); + break; + case V2: + this.steps = buildFieldPathV2(pathText); + break; + default: + throw new IllegalArgumentException("Unknown syntax version: " + version); + } + } + + private static List<String> buildFieldPathV2(String path) { + final List<String> steps = new ArrayList<>(); + // path character index to track backticks and dots and break path into steps + int idx = 0; + while (idx < path.length() && idx >= 0) { + if (path.charAt(idx) != BACKTICK) { + final int start = idx; + idx = path.indexOf(String.valueOf(DOT), idx); + if (idx >= 0) { // get path step and move forward + String field = path.substring(start, idx); + steps.add(field); + idx++; + } else { // add all + String field = path.substring(start); + steps.add(field); + } + } else { // has backtick + int backtickAt = idx; + idx++; + StringBuilder field = new StringBuilder(); + int start = idx; + while (true) { + // find closing backtick + idx = path.indexOf(String.valueOf(BACKTICK), idx); + if (idx == -1) { // if not found, then fail + failWhenIncompleteBacktickPair(path, backtickAt); + } + + // backtick escaped if right after backslash + boolean escaped = path.charAt(idx - 1) == BACKSLASH; + + if (idx >= path.length() - 1) { // at the end of path + if (escaped) { // but escaped, then fail + failWhenIncompleteBacktickPair(path, backtickAt); + } + field.append(path, start, idx); + // we've reached the end of the path, and the last character is the backtick + steps.add(field.toString()); + idx++; + break; + } + + if (path.charAt(idx + 1) != DOT) { // not followed by a dot + // this backtick isn't followed by a dot; include it in the field name, but continue + // looking for a matching backtick that is followed by a dot + idx++; + continue; + } + + if (escaped) { + // this backtick was escaped; include it in the field name, but continue + // looking for an unescaped matching backtick + field.append(path, start, idx - 1) + .append(BACKTICK); + + idx++; + start = idx; + continue; + } + + // we've found our matching backtick + field.append(path, start, idx); + steps.add(field.toString()); + idx += 2; // increment by two to include the backtick and the dot after it + break; + } + } + } + // add last step if last char is a dot + if (!path.isEmpty() && path.charAt(path.length() - 1) == DOT) + steps.add(""); + return Collections.unmodifiableList(steps); + } + + private static void failWhenIncompleteBacktickPair(String path, int backtickAt) { + throw new ConfigException("Incomplete backtick pair in path: [" + path + "]," + + " consider adding a backslash before backtick at position " + backtickAt + + " to escape it"); + } + + public String originalPath() { + return this.originalPath; + } + + + /** + * Access a {@code Field} at the current path within a schema {@code Schema} + * If field is not found, then {@code null} is returned. + */ + public Field fieldFrom(Schema schema) { + if (schema == null) return null; + + Schema current = schema; + for (String pathSegment : stepsWithoutLast()) { + final Field field = current.field(pathSegment); + if (field != null) { + current = field.schema(); + } else { + return null; + } + } + return current.field(lastStep()); + } + + /** + * Access a value at the current path within a schema-based {@code Struct} + * If object is not found, then {@code null} is returned. + */ + public Object valueFrom(Struct struct) { + if (struct == null) return null; + + Struct current = struct; + for (String pathSegment : stepsWithoutLast()) { + // Check to see if the field actually exists + if (current.schema().field(pathSegment) == null) { Review Comment: Should we also check if `current` is null, since even if the field is defined in the schema it might be optional? If so, I think that can replace the guard at line 177. (And we should probably add a test case for this.) -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
