org.apache.avro.io.parsing.JsonGrammarGenerator Maven / Gradle / Ivy
/**
* 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.avro.io.parsing;
import java.util.HashMap;
import java.util.Map;
import org.apache.avro.Schema;
import org.apache.avro.Schema.Field;
/**
* The class that generates a grammar suitable to parse Avro data
* in JSON format.
*/
public class JsonGrammarGenerator extends ValidatingGrammarGenerator {
/**
* Returns the non-terminal that is the start symbol
* for the grammar for the grammar for the given schema sc.
*/
public Symbol generate(Schema schema) {
return Symbol.root(generate(schema, new HashMap()));
}
/**
* Returns the non-terminal that is the start symbol
* for grammar of the given schema sc. If there is already an entry
* for the given schema in the given map seen then
* that entry is returned. Otherwise a new symbol is generated and
* an entry is inserted into the map.
* @param sc The schema for which the start symbol is required
* @param seen A map of schema to symbol mapping done so far.
* @return The start symbol for the schema
*/
public Symbol generate(Schema sc, Map seen) {
switch (sc.getType()) {
case NULL:
case BOOLEAN:
case INT:
case LONG:
case FLOAT:
case DOUBLE:
case STRING:
case BYTES:
case FIXED:
case UNION:
return super.generate(sc, seen);
case ENUM:
return Symbol.seq(new Symbol.EnumLabelsAction(sc.getEnumSymbols()),
Symbol.ENUM);
case ARRAY:
return Symbol.seq(Symbol.repeat(Symbol.ARRAY_END,
Symbol.ITEM_END, generate(sc.getElementType(), seen)),
Symbol.ARRAY_START);
case MAP:
return Symbol.seq(Symbol.repeat(Symbol.MAP_END,
Symbol.ITEM_END, generate(sc.getValueType(), seen),
Symbol.MAP_KEY_MARKER, Symbol.STRING),
Symbol.MAP_START);
case RECORD: {
LitS wsc = new LitS(sc);
Symbol rresult = seen.get(wsc);
if (rresult == null) {
Symbol[] production = new Symbol[sc.getFields().size() * 2 + 2];
rresult = Symbol.seq(production);
seen.put(wsc, rresult);
int i = production.length;
int n = 0;
production[--i] = Symbol.RECORD_START;
for (Field f : sc.getFields()) {
production[--i] = new Symbol.FieldAdjustAction(n, f.name());
production[--i] = generate(f.schema(), seen);
n++;
}
production[--i] = Symbol.RECORD_END;
}
return rresult;
}
default:
throw new RuntimeException("Unexpected schema type");
}
}
}