/*
* 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 com.facebook.presto.kafka.decoder.json;
import com.facebook.presto.kafka.KafkaColumnHandle;
import com.facebook.presto.kafka.KafkaFieldValueProvider;
import com.facebook.presto.kafka.decoder.KafkaFieldDecoder;
import com.facebook.presto.kafka.decoder.KafkaRowDecoder;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.MissingNode;
import com.google.common.base.Splitter;
import javax.inject.Inject;
import java.util.List;
import java.util.Map;
import java.util.Set;
import static com.google.common.base.Preconditions.checkState;
/**
* JSON specific Kafka row decoder.
*/
public class JsonKafkaRowDecoder
implements KafkaRowDecoder
{
public static final String NAME = "json";
private final ObjectMapper objectMapper;
@Inject
JsonKafkaRowDecoder(ObjectMapper objectMapper)
{
this.objectMapper = objectMapper;
}
@Override
public String getName()
{
return NAME;
}
@Override
public boolean decodeRow(byte[] data, Set<KafkaFieldValueProvider> fieldValueProviders, List<KafkaColumnHandle> columnHandles, Map<KafkaColumnHandle, KafkaFieldDecoder<?>> fieldDecoders)
{
JsonNode tree;
try {
tree = objectMapper.readTree(data);
}
catch (Exception e) {
return true;
}
for (KafkaColumnHandle columnHandle : columnHandles) {
if (columnHandle.isInternal()) {
continue;
}
@SuppressWarnings("unchecked")
KafkaFieldDecoder<JsonNode> decoder = (KafkaFieldDecoder<JsonNode>) fieldDecoders.get(columnHandle);
if (decoder != null) {
JsonNode node = locateNode(tree, columnHandle);
fieldValueProviders.add(decoder.decode(node, columnHandle));
}
}
return false;
}
private static JsonNode locateNode(JsonNode tree, KafkaColumnHandle columnHandle)
{
String mapping = columnHandle.getMapping();
checkState(mapping != null, "No mapping for %s", columnHandle.getName());
JsonNode currentNode = tree;
for (String pathElement : Splitter.on('/').omitEmptyStrings().split(mapping)) {
if (!currentNode.has(pathElement)) {
return MissingNode.getInstance();
}
currentNode = currentNode.path(pathElement);
}
return currentNode;
}
}