org.apache.thrift.partial.EnumCache Maven / Gradle / Ivy
/*
* 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.thrift.partial;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import org.apache.thrift.TEnum;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Provides a memoized way to lookup an enum by its value.
*
* This class is used internally by {@code TDeserializer}. It is not intended to be used
* separately on its own.
*/
public class EnumCache {
private static final Logger LOG = LoggerFactory.getLogger(EnumCache.class);
private Map, Map> classMap;
public EnumCache() {
this.classMap = new HashMap<>();
}
/**
* Gets an instance of the enum type {@code enumClass} corresponding to the given {@code value}.
*
* @param enumClass class of the enum to be returned.
* @param value value returned by {@code getValue()}.
*/
public TEnum get(Class enumClass, int value) {
Validate.checkNotNull(enumClass, "enumClass");
Map valueMap = classMap.get(enumClass);
if (valueMap == null) {
valueMap = addClass(enumClass);
if (valueMap == null) {
return null;
}
}
return valueMap.get(value);
}
private Map addClass(Class enumClass) {
try {
Method valuesMethod = enumClass.getMethod("values");
TEnum[] enumValues = (TEnum[]) valuesMethod.invoke(null);
Map valueMap = new HashMap<>();
for (TEnum enumValue : enumValues) {
valueMap.put(enumValue.getValue(), enumValue);
}
classMap.put(enumClass, valueMap);
return valueMap;
} catch (NoSuchMethodException e) {
LOG.error("enum class does not have values() method", e);
return null;
} catch (IllegalAccessException e) {
LOG.error("Enum.values() method should be public!", e);
return null;
} catch (InvocationTargetException e) {
LOG.error("Enum.values() threw exception", e);
return null;
}
}
}