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/*
* 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.meta_data;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.thrift.TBase;
import org.apache.thrift.TFieldIdEnum;
/**
* This class is used to store meta data about thrift fields. Every field in a
* a struct should have a corresponding instance of this class describing it.
*
* The meta data is registered by ALL Thrift struct classes via a static {...}
* initializer block in the generated Thrift code.
*
* Since different threads could be initializing different Thrift classes, calls
* to the public static methods of this class could be racy.
*
* All methods of this class should be made thread safe.
*/
public class FieldMetaData implements java.io.Serializable {
public final String fieldName;
public final byte requirementType;
public final FieldValueMetaData valueMetaData;
private static final Map<Class<? extends TBase>, Map<? extends TFieldIdEnum, FieldMetaData>> structMap;
static {
structMap = new ConcurrentHashMap<Class<? extends TBase>, Map<? extends TFieldIdEnum, FieldMetaData>>();
}
public FieldMetaData(String name, byte req, FieldValueMetaData vMetaData){
this.fieldName = name;
this.requirementType = req;
this.valueMetaData = vMetaData;
}
public static void addStructMetaDataMap(Class<? extends TBase> sClass, Map<? extends TFieldIdEnum, FieldMetaData> map){
structMap.put(sClass, map);
}
/**
* Returns a map with metadata (i.e. instances of FieldMetaData) that
* describe the fields of the given class.
*
* @param sClass The TBase class for which the metadata map is requested. It is not
* guaranteed that sClass will have been statically initialized before
* this method is called. A racy call to
* {@link FieldMetaData#addStructMetaDataMap(Class, Map)} from a different
* thread during static initialization of the Thrift class is possible.
*/
public static Map<? extends TFieldIdEnum, FieldMetaData> getStructMetaDataMap(
Class<? extends TBase> sClass) {
// Note: Do not use synchronized on this method declaration - it leads to a deadlock.
// Similarly, do not trigger sClass.newInstance() while holding a lock on structMap,
// it will lead to the same deadlock.
// See: https://issues.apache.org/jira/browse/THRIFT-5430 for details.
if (!structMap.containsKey(sClass)){ // Load class if it hasn't been loaded
try{
sClass.newInstance();
} catch (InstantiationException e){
throw new RuntimeException("InstantiationException for TBase class: " + sClass.getName() + ", message: " + e.getMessage());
} catch (IllegalAccessException e){
throw new RuntimeException("IllegalAccessException for TBase class: " + sClass.getName() + ", message: " + e.getMessage());
}
}
return structMap.get(sClass);
}
}
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