| /* |
| * 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.drill.exec.store.easy.json.parser; |
| |
| import com.fasterxml.jackson.core.JsonToken; |
| |
| /** |
| * Represents an empty array: the case where the parser has seen only |
| * {@code []}, but no array elements which would indicate the type. |
| * Resolves to a specific type upon |
| * presentation of the first element. If that element is |
| * {@code null}, we must still choose a type to record nulls. |
| * <p> |
| * This array listener holds no element since none has been |
| * created yet; we use this only while we see empty arrays. |
| */ |
| public abstract class EmptyArrayParser extends AbstractElementParser { |
| |
| protected final String key; |
| |
| public EmptyArrayParser(JsonStructureParser structParser, String key) { |
| super(structParser); |
| this.key = key; |
| } |
| |
| @Override |
| public void parse(TokenIterator tokenizer) { |
| JsonToken token1 = tokenizer.requireNext(); |
| |
| // Ignore null: treat as an empty array. |
| if (token1 == JsonToken.VALUE_NULL) { |
| return; |
| } |
| |
| // Assume an scalar is a one-item array. |
| if (token1 != JsonToken.START_ARRAY) { |
| tokenizer.unget(token1); |
| resolve(tokenizer).parse(tokenizer); |
| |
| // This parser never called again |
| return; |
| } |
| |
| // Ignore an empty array, resolve a non-empty array. |
| // Must be done even if the array value is null so elements |
| // can be counted. |
| JsonToken token2 = tokenizer.requireNext(); |
| if (token2 != JsonToken.END_ARRAY) { |
| |
| // Saw the first actual element. Swap out this parser for a |
| // real field parser, then let that parser parse from here. |
| // The real parser is for the entire field, so we unget the |
| // opening bracket as well as the element. |
| tokenizer.unget(token2); |
| tokenizer.unget(token1); |
| resolve(tokenizer).parse(tokenizer); |
| |
| // This parser never called again |
| } |
| } |
| |
| /** |
| * Replace this parser with a new parser based on the current |
| * parse context. |
| */ |
| protected abstract ElementParser resolve(TokenIterator tokenizer); |
| } |