org.apache.thrift.meta_data.FieldMetaData Maven / Gradle / Ivy
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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.Collections;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
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 final Map fieldAnnotations;
private static final ConcurrentMap<
Class, Map>
structMap = new ConcurrentHashMap<>();
public FieldMetaData(String name, byte req, FieldValueMetaData vMetaData) {
this(name, req, vMetaData, Collections.emptyMap());
}
public FieldMetaData(
String fieldName,
byte requirementType,
FieldValueMetaData valueMetaData,
Map fieldAnnotations) {
this.fieldName = fieldName;
this.requirementType = requirementType;
this.valueMetaData = valueMetaData;
this.fieldAnnotations = fieldAnnotations;
}
/**
* @return an unmodifiable view of the annotations for this field, empty if no annotations present
* or code gen param is not turned on
*/
public Map getFieldAnnotations() {
return Collections.unmodifiableMap(fieldAnnotations);
}
public static , F extends TFieldIdEnum> void addStructMetaDataMap(
Class sClass, Map 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 , F extends TFieldIdEnum>
Map getStructMetaDataMap(Class 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.getDeclaredConstructor().newInstance();
} catch (ReflectiveOperationException e) {
throw new RuntimeException(
e.getClass().getSimpleName() + " for TBase class: " + sClass.getName(), e);
}
}
//noinspection unchecked
return (Map) structMap.get(sClass);
}
}