org.apache.hive.hcatalog.common.HCatContext Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* 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
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* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.hive.hcatalog.common;
import com.facebook.presto.hive.$internal.com.google.common.base.Optional;
import com.facebook.presto.hive.$internal.com.google.common.base.Preconditions;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hive.common.classification.InterfaceAudience;
import org.apache.hadoop.hive.common.classification.InterfaceStability;
import java.util.Map;
/**
* HCatContext is a singleton that provides global access to configuration data.
*
* HCatalog provides a variety of functionality that users can configure at runtime through
* configuration properties. Available configuration properties are defined in
* {@link HCatConstants}. HCatContext allows users to enable optional functionality by
* setting properties in a provided configuration.
*
* HCatalog users (MR apps, processing framework adapters) should set properties
* in a configuration that has been provided to
* {@link #setConf(org.apache.hadoop.conf.Configuration)} to enable optional functionality.
* The job configuration must be used to ensure properties are passed to the backend MR tasks.
*
* HCatalog developers should enable optional functionality by checking properties
* from {@link #getConf()}. Since users are not obligated to set a configuration, optional
* functionality must provide a sensible default.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public enum HCatContext {
INSTANCE;
private Configuration conf = null;
/**
* Use the given configuration for optional behavior. Keys exclusive to an existing config
* are set in the new conf. The job conf must be used to ensure properties are passed to
* backend MR tasks.
*/
public synchronized HCatContext setConf(Configuration newConf) {
Preconditions.checkNotNull(newConf, "Required parameter 'newConf' must not be null.");
if (conf == null) {
conf = newConf;
return this;
}
for (Map.Entry entry : conf) {
if ((entry.getKey().matches("hcat.*")) && (newConf.get(entry.getKey()) == null)) {
newConf.set(entry.getKey(), entry.getValue());
}
}
conf = newConf;
return this;
}
/**
* Get the configuration, if there is one. Users are not required to setup HCatContext
* unless they wish to override default behavior, so the configuration may not be present.
*
* @return an Optional that might contain a Configuration
*/
public Optional getConf() {
return Optional.fromNullable(conf);
}
}