steveloughran commented on code in PR #3415: URL: https://github.com/apache/parquet-java/pull/3415#discussion_r3073217710
########## parquet-variant/src/main/java/org/apache/parquet/variant/VariantJsonParser.java: ########## @@ -0,0 +1,191 @@ +/* + * 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.parquet.variant; + +import com.fasterxml.jackson.core.JsonFactory; +import com.fasterxml.jackson.core.JsonParseException; +import com.fasterxml.jackson.core.JsonParser; +import com.fasterxml.jackson.core.JsonToken; +import com.fasterxml.jackson.core.StreamReadConstraints; +import com.fasterxml.jackson.core.exc.InputCoercionException; +import java.io.IOException; +import java.math.BigDecimal; + +/** + * Parses JSON into {@link Variant} values using Jackson streaming. + * + * <p>This class isolates the Jackson dependency from {@link VariantBuilder}, + * so that core variant construction does not require Jackson on the classpath. + * + * <p>Ported from Apache Spark's {@code VariantBuilder.parseJson}. + */ +public final class VariantJsonParser { + + private static final JsonFactory JSON_FACTORY = JsonFactory.builder() + .streamReadConstraints(StreamReadConstraints.builder() + .maxNestingDepth(500) + .maxStringLength(10_000_000) + .maxDocumentLength(50_000_000L) + .build()) + .build(); + + private VariantJsonParser() {} + + /** + * Parses a JSON string and returns the corresponding {@link Variant}. + * + * <p>Uses Jackson streaming parser for single-pass conversion + * with no intermediate tree. Number handling preserves precision: + * integers use the smallest fitting type, floating-point numbers + * prefer decimal encoding (no scientific notation) and fall back + * to double. + * + * @param json the JSON string to parse + * @return the parsed Variant + * @throws IOException if the JSON is malformed or an I/O error occurs + */ + public static Variant parseJson(String json) throws IOException { + try (JsonParser parser = JSON_FACTORY.createParser(json)) { + parser.nextToken(); + return parseJson(parser); + } + } + + /** + * Parses a JSON value from an already-positioned {@link JsonParser} + * and returns the corresponding {@link Variant}. The parser must + * have its current token set (i.e., {@code parser.nextToken()} + * or equivalent must have been called). + * + * @param parser a positioned Jackson JsonParser + * @return the parsed Variant + * @throws IOException if the JSON is malformed or an I/O error occurs + */ + public static Variant parseJson(JsonParser parser) throws IOException { + VariantBuilder builder = new VariantBuilder(); + buildJson(builder, parser); + return builder.build(); + } + + /** + * Recursively builds a Variant value from the current position of a + * Jackson streaming parser. Handles objects, arrays, strings, numbers + * (int/long/decimal/double), booleans, and null. + */ + private static void buildJson(VariantBuilder builder, JsonParser parser) throws IOException { + JsonToken token = parser.currentToken(); + if (token == null) { + throw new JsonParseException(parser, "Unexpected null token"); + } + switch (token) { + case START_OBJECT: + buildJsonObject(builder, parser); + break; + case START_ARRAY: + buildJsonArray(builder, parser); + break; + case VALUE_STRING: + builder.appendString(parser.getText()); + break; + case VALUE_NUMBER_INT: + buildJsonInteger(builder, parser); + break; + case VALUE_NUMBER_FLOAT: + buildJsonFloat(builder, parser); + break; + case VALUE_TRUE: + builder.appendBoolean(true); + break; + case VALUE_FALSE: + builder.appendBoolean(false); + break; + case VALUE_NULL: + builder.appendNull(); + break; + default: + throw new JsonParseException(parser, "Unexpected token " + token); + } + } + + private static void buildJsonObject(VariantBuilder builder, JsonParser parser) throws IOException { Review Comment: nit: add javadoc explaining how this will co-recurse into buildJSON ########## parquet-variant/src/main/java/org/apache/parquet/variant/VariantJsonParser.java: ########## @@ -0,0 +1,191 @@ +/* + * 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.parquet.variant; + +import com.fasterxml.jackson.core.JsonFactory; +import com.fasterxml.jackson.core.JsonParseException; +import com.fasterxml.jackson.core.JsonParser; +import com.fasterxml.jackson.core.JsonToken; +import com.fasterxml.jackson.core.StreamReadConstraints; +import com.fasterxml.jackson.core.exc.InputCoercionException; +import java.io.IOException; +import java.math.BigDecimal; + +/** + * Parses JSON into {@link Variant} values using Jackson streaming. + * + * <p>This class isolates the Jackson dependency from {@link VariantBuilder}, + * so that core variant construction does not require Jackson on the classpath. + * + * <p>Ported from Apache Spark's {@code VariantBuilder.parseJson}. + */ +public final class VariantJsonParser { + + private static final JsonFactory JSON_FACTORY = JsonFactory.builder() + .streamReadConstraints(StreamReadConstraints.builder() + .maxNestingDepth(500) + .maxStringLength(10_000_000) + .maxDocumentLength(50_000_000L) + .build()) + .build(); + + private VariantJsonParser() {} + + /** + * Parses a JSON string and returns the corresponding {@link Variant}. + * + * <p>Uses Jackson streaming parser for single-pass conversion + * with no intermediate tree. Number handling preserves precision: + * integers use the smallest fitting type, floating-point numbers + * prefer decimal encoding (no scientific notation) and fall back + * to double. + * + * @param json the JSON string to parse + * @return the parsed Variant + * @throws IOException if the JSON is malformed or an I/O error occurs + */ + public static Variant parseJson(String json) throws IOException { + try (JsonParser parser = JSON_FACTORY.createParser(json)) { + parser.nextToken(); + return parseJson(parser); + } + } + + /** + * Parses a JSON value from an already-positioned {@link JsonParser} + * and returns the corresponding {@link Variant}. The parser must + * have its current token set (i.e., {@code parser.nextToken()} + * or equivalent must have been called). + * + * @param parser a positioned Jackson JsonParser + * @return the parsed Variant + * @throws IOException if the JSON is malformed or an I/O error occurs + */ + public static Variant parseJson(JsonParser parser) throws IOException { + VariantBuilder builder = new VariantBuilder(); + buildJson(builder, parser); + return builder.build(); + } + + /** + * Recursively builds a Variant value from the current position of a + * Jackson streaming parser. Handles objects, arrays, strings, numbers + * (int/long/decimal/double), booleans, and null. + */ + private static void buildJson(VariantBuilder builder, JsonParser parser) throws IOException { + JsonToken token = parser.currentToken(); + if (token == null) { + throw new JsonParseException(parser, "Unexpected null token"); + } + switch (token) { + case START_OBJECT: + buildJsonObject(builder, parser); + break; + case START_ARRAY: + buildJsonArray(builder, parser); + break; + case VALUE_STRING: + builder.appendString(parser.getText()); + break; + case VALUE_NUMBER_INT: + buildJsonInteger(builder, parser); + break; + case VALUE_NUMBER_FLOAT: + buildJsonFloat(builder, parser); + break; + case VALUE_TRUE: + builder.appendBoolean(true); + break; + case VALUE_FALSE: + builder.appendBoolean(false); + break; + case VALUE_NULL: + builder.appendNull(); + break; + default: + throw new JsonParseException(parser, "Unexpected token " + token); + } + } + + private static void buildJsonObject(VariantBuilder builder, JsonParser parser) throws IOException { + VariantObjectBuilder obj = builder.startObject(); + while (parser.nextToken() != JsonToken.END_OBJECT) { + obj.appendKey(parser.currentName()); + parser.nextToken(); + buildJson(obj, parser); + } + builder.endObject(); + } + + private static void buildJsonArray(VariantBuilder builder, JsonParser parser) throws IOException { Review Comment: same comment as above: mention co-recursion -- This is an automated message from the Apache Git Service. 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