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/*
* ============LICENSE_START=======================================================
* ONAP
* ================================================================================
* Copyright (C) 2018-2020 AT&T Intellectual Property. 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.
* 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.drools.pooling;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import java.util.HashMap;
import java.util.Map;
import org.onap.policy.drools.pooling.message.Heartbeat;
import org.onap.policy.drools.pooling.message.Identification;
import org.onap.policy.drools.pooling.message.Leader;
import org.onap.policy.drools.pooling.message.Message;
import org.onap.policy.drools.pooling.message.Offline;
import org.onap.policy.drools.pooling.message.Query;
/**
* Serialization helper functions.
*/
public class Serializer {
/**
* The message type is stored in fields of this name within the JSON.
*/
private static final String TYPE_FIELD = "type";
/**
* Used to encode & decode JSON messages sent & received, respectively, on the
* internal DMaaP topic.
*/
private final Gson gson = new Gson();
/**
* Maps a message subclass to its type.
*/
private static final Map<Class<? extends Message>, String> class2type = new HashMap<>();
/**
* Maps a message type to the appropriate subclass.
*/
private static final Map<String, Class<? extends Message>> type2class = new HashMap<>();
static {
class2type.put(Heartbeat.class, "heartbeat");
class2type.put(Identification.class, "identification");
class2type.put(Leader.class, "leader");
class2type.put(Offline.class, "offline");
class2type.put(Query.class, "query");
class2type.forEach((clazz, type) -> type2class.put(type, clazz));
}
/**
* Constructor.
*/
public Serializer() {
super();
}
/**
* Encodes a filter.
*
* @param filter filter to be encoded
* @return the filter, serialized as a JSON string
*/
public String encodeFilter(Map<String, Object> filter) {
return gson.toJson(filter);
}
/**
* Encodes a message.
*
* @param msg message to be encoded
* @return the message, serialized as a JSON string
*/
public String encodeMsg(Message msg) {
JsonElement jsonEl = gson.toJsonTree(msg);
String type = class2type.get(msg.getClass());
if (type == null) {
throw new JsonParseException("cannot serialize " + msg.getClass());
}
jsonEl.getAsJsonObject().addProperty(TYPE_FIELD, type);
return gson.toJson(jsonEl);
}
/**
* Decodes a JSON string into a Message.
*
* @param msg JSON string representing the message
* @return the message
*/
public Message decodeMsg(String msg) {
JsonElement jsonEl = gson.fromJson(msg, JsonElement.class);
JsonElement typeEl = jsonEl.getAsJsonObject().get(TYPE_FIELD);
if (typeEl == null) {
throw new JsonParseException("cannot deserialize " + Message.class
+ " because it does not contain a field named " + TYPE_FIELD);
}
Class<? extends Message> clazz = type2class.get(typeEl.getAsString());
if (clazz == null) {
throw new JsonParseException("cannot deserialize " + typeEl);
}
return gson.fromJson(jsonEl, clazz);
}
}
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