C0urante commented on code in PR #12637: URL: https://github.com/apache/kafka/pull/12637#discussion_r1149375240
########## connect/transforms/src/main/java/org/apache/kafka/connect/transforms/field/SingleFieldPath.java: ########## @@ -0,0 +1,585 @@ +/* + * 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.cache.Cache; +import org.apache.kafka.common.cache.LRUCache; +import org.apache.kafka.common.cache.SynchronizedCache; +import org.apache.kafka.connect.data.Field; +import org.apache.kafka.connect.data.Schema; +import org.apache.kafka.connect.data.Schema.Type; +import org.apache.kafka.connect.data.SchemaBuilder; +import org.apache.kafka.connect.data.Struct; +import org.apache.kafka.connect.transforms.util.SchemaUtil; + +import java.util.ArrayList; +import java.util.Arrays; +import java.util.HashMap; +import java.util.List; +import java.util.Map; + +/** + * A FieldPath is composed by one or many field names, known as steps, + * to access values within a data object (either {@code Struct} or {@code Map<String, Object>}).a + * <p> + * If the SMT requires accessing multiple fields on the same data object, + * use {@code FieldPaths} instead. + * <p> + * The field path semantics are defined by the syntax version {@code FieldSyntaxVersion}. + * <p> + * Paths are calculated once and cached for further access. + * <p> + * Invariants: + * <li> + * <ul>A field path can contain one or more steps</ul> + * </li> + * + * See KIP-821. + * + * @see FieldSyntaxVersion + * @see MultiFieldPaths + */ +public class SingleFieldPath implements FieldPath { + + private static final char BACKTICK_CHAR = '`'; + private static final char DOT_CHAR = '.'; + private static final char BACKSLASH_CHAR = '\\'; + + private static final Cache<String, SingleFieldPath> PATHS_CACHE = new SynchronizedCache<>(new LRUCache<>(16)); + + private final String[] path; + + static SingleFieldPath ofV1(String field) { + return of(field, FieldSyntaxVersion.V1); + } + + static SingleFieldPath ofV2(String field) { + return of(field, FieldSyntaxVersion.V2); + } + + /** + * If version is V2, then paths are cached for further access. + * + * @param field field path expression + * @param version field syntax version + */ + public static SingleFieldPath of(String field, FieldSyntaxVersion version) { + if ((field == null || field.isEmpty()) // empty path + || version.equals(FieldSyntaxVersion.V1)) { // or V1 + return new SingleFieldPath(field, version); + } else { // use cache when V2 + final SingleFieldPath found = PATHS_CACHE.get(field); + if (found != null) { + return found; + } else { + final SingleFieldPath fieldPath = new SingleFieldPath(field, version); + PATHS_CACHE.put(field, fieldPath); + return fieldPath; + } + } + } + + SingleFieldPath(String pathText, FieldSyntaxVersion version) { + if (pathText == null || pathText.isEmpty()) { // empty path + this.path = new String[] {}; + } else { + switch (version) { + case V1: // backward compatibility + this.path = new String[] {pathText}; + break; + case V2: + path = buildFieldPathV2(pathText); + break; + default: + throw new IllegalArgumentException("Unknown syntax version: " + version); + } + } + } + + private String[] buildFieldPathV2(String pathText) { + // if no dots or wrapping backticks are used, then return path with single step + if (!pathText.contains(String.valueOf(DOT_CHAR))) { + return new String[] {pathText}; + } else { + // prepare for tracking path steps + final List<String> steps = new ArrayList<>(); + // avoid creating new string on changes + final StringBuilder s = new StringBuilder(pathText); + + while (s.length() > 0) { // until path is traversed + // start processing backtick pair, if any + if (s.charAt(0) == BACKTICK_CHAR) { + s.deleteCharAt(0); + + // find backtick closing pair + int idx = 0; + while (idx >= 0) { + idx = s.indexOf(String.valueOf(BACKTICK_CHAR), idx); + if (idx == -1) { // if not found, fail + throw new IllegalArgumentException("Incomplete backtick pair at [...]`" + s); + } + // check that it is not escaped or wrapped in another backticks pair + if (idx < s.length() - 1 // not wrapping the whole field path + && (s.charAt(idx + 1) != DOT_CHAR // not wrapping + || s.charAt(idx - 1) == BACKSLASH_CHAR)) { // ... or escaped + idx++; // move index forward and keep searching + } else { // it's the closing pair + steps.add(escapeBackticks(s.substring(0, idx))); + s.delete(0, idx + 2); // rm backtick and dot + break; + } + } + } else { // process dots in path + final int atDot = s.indexOf(String.valueOf(DOT_CHAR)); + if (atDot > 0) { // get path step and move forward + steps.add(escapeBackticks(s.substring(0, atDot))); + s.delete(0, atDot + 1); + } else { // add all + steps.add(escapeBackticks(s.toString())); + s.delete(0, s.length()); + } + } + } + + return steps.toArray(new String[0]); + } + } + + /** + * Return field name with escaped backticks, if any. + * + * @param field potentially containing backticks + * @throws IllegalArgumentException when there are incomplete backtick pairs + */ + private String escapeBackticks(String field) { + final StringBuilder s = new StringBuilder(field); + int idx = 0; + while (idx >= 0) { + idx = s.indexOf(String.valueOf(BACKTICK_CHAR), idx + 1); + if (idx >= 1 && s.length() > 2) { + if (s.charAt(idx - 1) == DOT_CHAR + || (idx < s.length() - 1 && s.charAt(idx + 1) == DOT_CHAR + && s.charAt(idx - 1) != BACKSLASH_CHAR)) { + throw new IllegalArgumentException("Incomplete backtick pair at [...]" + field); + } + if (s.charAt(idx - 1) == BACKSLASH_CHAR) { // escape backtick + if ((idx == 1 && s.charAt(0) == BACKSLASH_CHAR) // at the beginning: \`foo[...] + || idx == s.length() - 1) { // at the end: [...]baz\` + s.deleteCharAt(idx - 1); + } else if ((idx > 2 && s.charAt(idx - 2) == DOT_CHAR) // after a dot: [...].\`bar[...] + || (idx < s.length() - 1 && s.charAt(idx + 1) == DOT_CHAR)) { // before a dot: [...]bar\`.[...] + s.deleteCharAt(idx - 1); + } + } + } + } + return s.toString(); + } Review Comment: I took a stab at simplifying this whole method to 1) remove unnecessary `StringBuilder` instantiation, 2) handle all backtick escape logic on the fly (instead of in a follow-up step with the `escapeBackticks` method), and 3) follow the slightly-tweaked spec I outlined in my latest comment. LMKWYT ```suggestion private String[] buildFieldPathV2(String pathText) { final List<String> steps = new ArrayList<>(); int idx = 0; while (idx < pathText.length() && idx >= 0) { if (pathText.charAt(idx) != BACKTICK_CHAR) { final int start = idx; idx = pathText.indexOf(String.valueOf(DOT_CHAR), idx); if (idx > 0) { // get path step and move forward String field = pathText.substring(start, idx); steps.add(field); idx++; } else { // add all String field = pathText.substring(start); steps.add(field); } } else { StringBuilder field = new StringBuilder(); idx++; int start = idx; while (true) { idx = pathText.indexOf(String.valueOf(BACKTICK_CHAR), idx); if (idx == -1) { // if not found, fail throw new IllegalArgumentException("Incomplete backtick pair in path: " + pathText); } boolean endOfPath = idx >= pathText.length() - 1; if (endOfPath) { field.append(pathText, start, idx); // we've reached the end of the path, and the last character is the backtick steps.add(field.toString()); idx++; break; } if (pathText.charAt(idx + 1) != DOT_CHAR) { // 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 (pathText.charAt(idx - 1) == BACKSLASH_CHAR) { // this backtick was escaped; include it in the field name, but continue // looking for an unescaped matching backtick field.append(pathText, start, idx - 1) .append(BACKTICK_CHAR); idx++; start = idx; continue; } // we've found our matching backtick field.append(pathText, start, idx); steps.add(field.toString()); idx += 2; // increment by two to include the backtick and the dot after it break; } } } return steps.toArray(new String[0]); } ``` -- This is an automated message from the Apache Git Service. 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