/*
* Copyright 2015-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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 com.amazonaws.util.json;
import com.amazonaws.AmazonClientException;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
/**
* A utility class to process JSON contents.
*/
public class JsonUtils {
private static volatile AwsJsonFactory factory = new GsonFactory();
/**
* JSON engine
*/
public static enum JsonEngine {
/**
* An engine powered by the build-in {@link JsonReader} and
* {@link JsonWriter} available since Android API 11.
*/
// Android,
/**
* An engine powered by Gson.
*
* @see <a href="https://code.google.com/p/google-gson/">Gson</a>
*/
Gson,
/**
* An engine powered by Jackson 2.x. It's the fastest engine.
*
* @see <a
* href="https://github.com/FasterXML/jackson-core">jackson-core</a>
*/
Jackson
}
/**
* Sets the JSON engine. Default is Gson.
*
* @param jsonEngine
*/
public static void setJsonEngine(JsonEngine jsonEngine) {
switch (jsonEngine) {
case Gson:
factory = new GsonFactory();
break;
case Jackson:
factory = new JacksonFactory();
break;
default:
throw new RuntimeException("Unsupported json engine");
}
}
/**
* Sets the JSON engine.
*
* @param factory an {@link AwsJsonFactory}
*/
static void setJsonEngine(AwsJsonFactory factory) {
if (factory == null) {
throw new IllegalArgumentException("factory can't be null");
}
JsonUtils.factory = factory;
}
/**
* Gets a JSON reader. If no JSON engine is available, an
* {@link AmazonClientException} will be thrown.
*
* @param in reader
* @return a JSON reader
*/
public static AwsJsonReader getJsonReader(Reader in) {
if (factory == null) {
throw new IllegalStateException("Json engine is unavailable.");
}
return factory.getJsonReader(in);
}
/**
* Gets a JSON writer. If no JSON engine is available, an
* {@link AmazonClientException} will be thrown.
*
* @param out writer
* @return a JSON writer
*/
public static AwsJsonWriter getJsonWriter(Writer out) {
if (factory == null) {
throw new IllegalStateException("Json engine is unavailable.");
}
return factory.getJsonWriter(out);
}
/**
* Convenient method to convert a JSON string to a map. Any object or array
* will be discarded. Number and boolean are stored as string.
*
* @param in reader
* @return a non null, unmodifiable, string to string map
*/
@SuppressWarnings("unchecked")
public static Map<String, String> jsonToMap(Reader in) {
AwsJsonReader reader = getJsonReader(in);
try {
// in case it's empty
if (reader.peek() == null) {
return Collections.EMPTY_MAP;
}
Map<String, String> map = new HashMap<String, String>();
reader.beginObject();
while (reader.hasNext()) {
String key = reader.nextName();
if (reader.isContainer()) {
// skip non string nodes
reader.skipValue();
} else {
map.put(key, reader.nextString());
}
}
reader.endObject();
reader.close();
return Collections.unmodifiableMap(map);
} catch (IOException e) {
throw new AmazonClientException("Unable to parse JSON String.", e);
}
}
/**
* Convenient method to convert a JSON string to a map. Any object or array
* will be discarded. Number and boolean are stored as string.
*
* @param json a JSON encoding string
* @return a non null, unmodifiable, string to string map
*/
@SuppressWarnings("unchecked")
public static Map<String, String> jsonToMap(String json) {
if (json == null || json.isEmpty()) {
return Collections.EMPTY_MAP;
}
return jsonToMap(new StringReader(json));
}
/**
* Encode a string to string map as a JSON string.
*
* @param map map to be encoded
* @return a non null JSON string
*/
public static String mapToString(Map<String, String> map) {
if (map == null || map.isEmpty()) {
return "{}";
}
try {
StringWriter out = new StringWriter();
AwsJsonWriter writer = getJsonWriter(out);
writer.beginObject();
for (Map.Entry<String, String> entry : map.entrySet()) {
writer.name(entry.getKey()).value(entry.getValue());
}
writer.endObject();
writer.close();
return out.toString();
} catch (IOException e) {
throw new AmazonClientException("Unable to serialize to JSON String.", e);
}
}
/**
* A helper function to check whether a class is available.
*
* @param className full name of the class
* @return true if found, false otherwise
*/
@SuppressWarnings("unused")
private static boolean isClassAvailable(String className) {
try {
Class.forName(className);
return true;
} catch (Exception e) {
return false;
}
}
}