JsonSerDeser.java
/*
* 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.yarn.service.utils;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.SerializationFeature;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
/**
* Support for marshalling objects to and from JSON.
* This class is NOT thread safe; it constructs an object mapper
* as an instance field.
* @param <T>
*/
public class JsonSerDeser<T> {
private static final Logger log = LoggerFactory.getLogger(JsonSerDeser.class);
private final Class<T> classType;
private final ObjectMapper mapper;
/**
* Create an instance bound to a specific type
* @param classType class type
*/
@SuppressWarnings("deprecation")
public JsonSerDeser(Class<T> classType) {
this.classType = classType;
this.mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
mapper.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, false);
}
public JsonSerDeser(Class<T> classType, PropertyNamingStrategy namingStrategy) {
this(classType);
mapper.setPropertyNamingStrategy(namingStrategy);
}
/**
* Convert from JSON
* @param json input
* @return the parsed JSON
* @throws IOException IO
* @throws JsonMappingException failure to map from the JSON to this class
*/
public T fromJson(String json)
throws IOException, JsonParseException, JsonMappingException {
try {
return mapper.readValue(json, classType);
} catch (IOException e) {
log.error("Exception while parsing json : " + e + "\n" + json, e);
throw e;
}
}
/**
* Convert from a JSON file
* @param jsonFile input file
* @return the parsed JSON
* @throws IOException IO problems
* @throws JsonMappingException failure to map from the JSON to this class
*/
public T fromFile(File jsonFile)
throws IOException, JsonParseException, JsonMappingException {
File absoluteFile = jsonFile.getAbsoluteFile();
try {
return mapper.readValue(absoluteFile, classType);
} catch (IOException e) {
log.error("Exception while parsing json file {}", absoluteFile, e);
throw e;
}
}
/**
* Convert from a JSON file
* @param resource input file
* @return the parsed JSON
* @throws IOException IO problems
* @throws JsonMappingException failure to map from the JSON to this class
*/
public T fromResource(String resource)
throws IOException, JsonParseException, JsonMappingException {
try(InputStream resStream = this.getClass().getResourceAsStream(resource)) {
if (resStream == null) {
throw new FileNotFoundException(resource);
}
return (T) (mapper.readValue(resStream, classType));
} catch (IOException e) {
log.error("Exception while parsing json resource {}", resource, e);
throw e;
}
}
/**
* Convert from an input stream, closing the stream afterwards.
* @param stream
* @return the parsed JSON
* @throws IOException IO problems
*/
public T fromStream(InputStream stream) throws IOException {
try {
return (T) (mapper.readValue(stream, classType));
} catch (IOException e) {
log.error("Exception while parsing json input stream", e);
throw e;
} finally {
IOUtils.closeStream(stream);
}
}
/**
* clone by converting to JSON and back again.
* This is much less efficient than any Java clone process.
* @param instance instance to duplicate
* @return a new instance
* @throws IOException problems.
*/
public T fromInstance(T instance) throws IOException {
return fromJson(toJson(instance));
}
/**
* Deserialize from a byte array
* @param b
* @return the deserialized value
* @throws IOException parse problems
*/
public T fromBytes(byte[] b) throws IOException {
String json = new String(b, 0, b.length, StandardCharsets.UTF_8);
return fromJson(json);
}
/**
* Load from a Hadoop filesystem
* @param fs filesystem
* @param path path
* @return a loaded CD
* @throws IOException IO problems
* @throws JsonParseException parse problems
* @throws JsonMappingException O/J mapping problems
*/
public T load(FileSystem fs, Path path) throws IOException {
FSDataInputStream dataInputStream = fs.open(path);
return fromStream(dataInputStream);
}
/**
* Save to a hadoop filesystem
* @param fs filesystem
* @param path path
* @param instance instance to save
* @param overwrite should any existing file be overwritten
* @throws IOException IO exception
*/
public void save(FileSystem fs, Path path, T instance,
boolean overwrite) throws
IOException {
FSDataOutputStream dataOutputStream = fs.create(path, overwrite);
writeJsonAsBytes(instance, dataOutputStream);
}
/**
* Save an instance to a file
* @param instance instance to save
* @param file file
* @throws IOException
*/
public void save(T instance, File file) throws
IOException {
writeJsonAsBytes(instance, new FileOutputStream(file.getAbsoluteFile()));
}
/**
* Write the json as bytes -then close the file
* @param dataOutputStream an outout stream that will always be closed
* @throws IOException on any failure
*/
private void writeJsonAsBytes(T instance,
OutputStream dataOutputStream) throws IOException {
try {
String json = toJson(instance);
byte[] b = json.getBytes(StandardCharsets.UTF_8);
dataOutputStream.write(b);
dataOutputStream.flush();
dataOutputStream.close();
} finally {
IOUtils.closeStream(dataOutputStream);
}
}
/**
* Convert an object to a JSON string
* @param instance instance to convert
* @return a JSON string description
* @throws JsonProcessingException parse problems
*/
public String toJson(T instance) throws JsonProcessingException {
mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
return mapper.writeValueAsString(instance);
}
}