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/*
* Copyright 2014 Open Networking Laboratory
*
* 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.
*/
package org.onosproject.codec;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import java.util.ArrayList;
import java.util.List;
/**
* Abstraction of a codec capable for encoding/decoding arbitrary objects to/from JSON.
*/
public abstract class JsonCodec<T> {
/**
* Encodes the specified entity into JSON.
*
* @param entity entity to encode
* @param context encoding context
* @return JSON node
* @throws java.lang.UnsupportedOperationException if the codec does not
* support encode operations
*/
public ObjectNode encode(T entity, CodecContext context) {
throw new UnsupportedOperationException("encode() not supported");
}
/**
* Decodes the specified entity from JSON.
*
* @param json JSON to decode
* @param context decoding context
* @return decoded entity
* @throws java.lang.UnsupportedOperationException if the codec does not
* support decode operations
*/
public T decode(ObjectNode json, CodecContext context) {
throw new UnsupportedOperationException("decode() not supported");
}
/**
* Encodes the collection of the specified entities.
*
* @param entities collection of entities to encode
* @param context encoding context
* @return JSON array
* @throws java.lang.UnsupportedOperationException if the codec does not
* support encode operations
*/
public ArrayNode encode(Iterable<T> entities, CodecContext context) {
ArrayNode result = context.mapper().createArrayNode();
for (T entity : entities) {
result.add(encode(entity, context));
}
return result;
}
/**
* Decodes the specified JSON array into a collection of entities.
*
* @param json JSON array to decode
* @param context decoding context
* @return collection of decoded entities
* @throws java.lang.UnsupportedOperationException if the codec does not
* support decode operations
*/
public List<T> decode(ArrayNode json, CodecContext context) {
List<T> result = new ArrayList<>();
for (JsonNode node : json) {
result.add(decode((ObjectNode) node, context));
}
return result;
}
/**
* Gets a child Object Node from a parent by name. If the child is not found
* or does nor represent an object, null is returned.
*
* @param parent parent object
* @param childName name of child to query
* @return child object if found, null if not found or if not an object
*/
protected static ObjectNode get(ObjectNode parent, String childName) {
JsonNode node = parent.path(childName);
return node.isObject() && !node.isNull() ? (ObjectNode) node : null;
}
/**
* Gets a child Object Node from a parent by index. If the child is not found
* or does nor represent an object, null is returned.
*
* @param parent parent object
* @param childIndex index of child to query
* @return child object if found, null if not found or if not an object
*/
protected static ObjectNode get(JsonNode parent, int childIndex) {
JsonNode node = parent.path(childIndex);
return node.isObject() && !node.isNull() ? (ObjectNode) node : null;
}
}
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