/**
* 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.hadoop.tools.rumen;
import java.io.Closeable;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.compress.CodecPool;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.CompressionCodecFactory;
import org.apache.hadoop.io.compress.Decompressor;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
/**
* A simple wrapper for parsing JSON-encoded data using ObjectMapper.
* @param <T> The (base) type of the object(s) to be parsed by this parser.
*/
class JsonObjectMapperParser<T> implements Closeable {
private final ObjectMapper mapper;
private final Class<? extends T> clazz;
private final JsonParser jsonParser;
private final Decompressor decompressor;
/**
* Constructor.
*
* @param path
* Path to the JSON data file, possibly compressed.
* @param conf
* @throws IOException
*/
public JsonObjectMapperParser(Path path, Class<? extends T> clazz,
Configuration conf) throws IOException {
mapper = new ObjectMapper();
mapper.configure(
DeserializationConfig.Feature.CAN_OVERRIDE_ACCESS_MODIFIERS, true);
this.clazz = clazz;
FileSystem fs = path.getFileSystem(conf);
CompressionCodec codec = new CompressionCodecFactory(conf).getCodec(path);
InputStream input;
if (codec == null) {
input = fs.open(path);
decompressor = null;
} else {
FSDataInputStream fsdis = fs.open(path);
decompressor = CodecPool.getDecompressor(codec);
input = codec.createInputStream(fsdis, decompressor);
}
jsonParser = mapper.getJsonFactory().createJsonParser(input);
}
/**
* Constructor.
*
* @param input
* The input stream for the JSON data.
*/
public JsonObjectMapperParser(InputStream input, Class<? extends T> clazz)
throws IOException {
mapper = new ObjectMapper();
mapper.configure(
DeserializationConfig.Feature.CAN_OVERRIDE_ACCESS_MODIFIERS, true);
this.clazz = clazz;
decompressor = null;
jsonParser = mapper.getJsonFactory().createJsonParser(input);
}
/**
* Get the next object from the trace.
*
* @return The next instance of the object. Or null if we reach the end of
* stream.
* @throws IOException
*/
public T getNext() throws IOException {
try {
return mapper.readValue(jsonParser, clazz);
} catch (EOFException e) {
return null;
}
}
@Override
public void close() throws IOException {
try {
jsonParser.close();
} finally {
if (decompressor != null) {
CodecPool.returnDecompressor(decompressor);
}
}
}
}