manner commented on code in PR #29520: URL: https://github.com/apache/flink/pull/29520#discussion_r4513053293
########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/VariantToXmlWriter.java: ########## @@ -0,0 +1,784 @@ +/* + * 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.flink.table.runtime.functions; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.table.runtime.functions.XmlVariantNames.SchemaPrefix; +import org.apache.flink.types.variant.Variant; + +import org.w3c.dom.DOMException; +import org.w3c.dom.Document; + +import javax.annotation.Nullable; +import javax.xml.parsers.DocumentBuilderFactory; +import javax.xml.parsers.ParserConfigurationException; +import javax.xml.stream.XMLOutputFactory; +import javax.xml.stream.XMLStreamException; +import javax.xml.stream.XMLStreamWriter; + +import java.io.StringWriter; +import java.time.Instant; +import java.time.LocalDate; +import java.time.LocalDateTime; +import java.time.ZoneOffset; +import java.util.ArrayList; +import java.util.Base64; +import java.util.Collections; +import java.util.Comparator; +import java.util.EnumSet; +import java.util.HashMap; +import java.util.List; +import java.util.Map; +import java.util.Set; +import java.util.regex.Matcher; +import java.util.regex.Pattern; + +import static org.apache.flink.table.runtime.functions.XmlVariantNames.ATTRIBUTE_PREFIX; +import static org.apache.flink.table.runtime.functions.XmlVariantNames.ORDER_KEY; +import static org.apache.flink.table.runtime.functions.XmlVariantNames.TEXT_KEY; +import static org.apache.flink.table.runtime.functions.XmlVariantNames.XSI_NIL; +import static org.apache.flink.table.runtime.functions.XmlVariantNames.XSI_TYPE; +import static org.apache.flink.types.variant.BinaryVariantUtil.TIMESTAMP_FORMATTER; +import static org.apache.flink.types.variant.BinaryVariantUtil.TIMESTAMP_LTZ_FORMATTER; +import static org.apache.flink.types.variant.BinaryVariantUtil.TIME_FORMATTER; +import static org.apache.flink.util.Preconditions.checkArgument; +import static org.apache.flink.util.Preconditions.checkState; + +/** + * Writes a {@link Variant} as an XML string for {@code XML_STRING}. It reverses the mapping of + * {@link XmlToVariantParser}, so that parsing the XML string of a variant from {@code PARSE_XML} + * gives the same variant. The mapping is described in the documentation of {@code XML_STRING}. + * + * <p>The content of an element is written in the order of its {@code #} field. Content without a + * position in the {@code #} field follows in the order of its keys. A variant {@code NULL}, or a + * {@code NULL} text, is written as {@code xsi:nil="true"}, and a scalar other than a string or a + * UUID gets an {@code xsi:type}, e.g. {@code xsi:type="xs:int"}. If the document uses the xsi or xs + * prefix, the root element declares it with the namespace of XML Schema, unless the variant + * declares it on the root element itself. + * + * <p>The XML writer of the JDK writes the tags and escapes the text. It writes tabs and line breaks + * in attribute values, and carriage returns in text, as they are, so a parser reads them back as + * spaces and line feeds. + * + * <p>A variant fails with an {@link IllegalArgumentException} if it has no XML representation: + * + * <ul> + * <li>it isn't an object with a single field for the root element, or the root is an array, + * <li>a key isn't an XML name that {@code PARSE_XML} accepts, + * <li>a text or an attribute value has a character that XML 1.0 doesn't allow, e.g. U+0000, + * <li>an array is nested in an array, + * <li>an {@code @} field holds an object, an array, or a {@code NULL}, or a {@code $} field holds + * an object, + * <li>a {@code NULL} text isn't the only content of its element, or an element has an {@code + * @xsi:nil} field that is true and content, + * <li>a {@code #} field isn't an object, doesn't have one integer position for each item of a + * key, or has a position more than once, + * <li>an element would need two {@code xsi:type} or two {@code xsi:nil} attributes, e.g. an + * {@code @xsi:type} field and a typed text, or an {@code @xsi:nil} field and a {@code NULL} + * text. + * </ul> + */ +@Internal +public final class VariantToXmlWriter { + + private static final Set<Variant.Type> INTEGER_TYPES = + EnumSet.of( + Variant.Type.TINYINT, + Variant.Type.SMALLINT, + Variant.Type.INT, + Variant.Type.BIGINT); + + // The XML writer of the JDK, regardless of other StAX implementations on the classpath. Its + // factory creates a new writer for each call and keeps no state of it, so it can be shared. + private static final XMLOutputFactory OUTPUT_FACTORY = XMLOutputFactory.newDefaultFactory(); + + // Any character outside of the Char production of XML 1.0, see + // https://www.w3.org/TR/xml/#charsets. + private static final Pattern NON_XML_CHAR = + Pattern.compile("[^\t\n\r\u0020-\uD7FF\uE000-\uFFFD\\x{10000}-\\x{10FFFF}]"); + + // The DOM document that names are checked with. It isn't thread-safe, so each thread has its + // own. + private static final ThreadLocal<Document> NAME_DOCUMENT = + ThreadLocal.withInitial(VariantToXmlWriter::newDocument); + + // The document that is written, and the schema prefixes that it uses. + private final StringWriter output = new StringWriter(); + private final XMLStreamWriter xml; + private final Set<SchemaPrefix> usedSchemaPrefixes = EnumSet.noneOf(SchemaPrefix.class); + + private VariantToXmlWriter() { + try { + xml = OUTPUT_FACTORY.createXMLStreamWriter(output); + } catch (XMLStreamException e) { + // Only the message, since the location of the exception isn't serializable. + throw new IllegalStateException(e.getMessage()); + } + } + + public static String write(Variant variant) { + final String rootName = rootName(variant); + final Variant root = variant.getField(rootName); + checkRootIsNotArray(rootName, root); + return new VariantToXmlWriter().writeDocument(rootName, root); Review Comment: That doesn't work here, because `VariantToXmlWriter` holds some state that is needed for each call. `XMLStreamWriter` is also not thread safe, so each `write()` needs its own instance. -- This is an automated message from the Apache Git Service. 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