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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.config.subscription;
import com.yahoo.config.ConfigInstance;
/**
* This is a simple config getter that retrieves a config with a given class and configId through a
* simple method call. No subscription is retained when the config has been returned to the client.
*
* This class is mainly targeted to unit tests that do not want the extra complexity incurred by setting
* up their own subscriber. Another use-case is clients that get config, do a task, and exit, e.g.
* command-line tools.
*
* @author gjoranv
*/
public class ConfigGetter<T extends ConfigInstance> {
private final Class<T> clazz;
private final ConfigSource source;
/**
* Creates a ConfigGetter for class <code>clazz</code>
*
* @param clazz a config class
*/
public ConfigGetter(Class<T> clazz) {
this(null, clazz);
}
/**
* Creates a ConfigGetter for class <code>clazz</code> with the specified
* {@link ConfigSource}.
*
* @param source a {@link ConfigSource}
* @param clazz a config class
*/
public ConfigGetter(ConfigSource source, Class<T> clazz) {
this.clazz = clazz;
this.source = source;
}
/**
* Returns an instance of the config class specified in the constructor.
*
* @param configId a config id to use when getting the config
* @return an instance of a config class
*/
public synchronized T getConfig(String configId) {
ConfigSubscriber subscriber;
ConfigHandle<T> h;
if (source == null) {
subscriber = new ConfigSubscriber();
} else {
subscriber = new ConfigSubscriber(source);
}
h = subscriber.subscribe(clazz, configId);
subscriber.nextConfig();
T ret = h.getConfig();
subscriber.close();
return ret;
}
/**
* Creates a ConfigGetter instance and returns an instance of the config class <code>c</code>.
*
* @param c a config class
* @param configId a config id to use when getting the config
* @return an instance of a config class
*/
public static <T extends ConfigInstance> T getConfig(Class<T> c, String configId) {
ConfigGetter<T> getter = new ConfigGetter<T>(c);
return getter.getConfig(configId);
}
/**
* Creates a ConfigGetter instance and returns an instance of the config class <code>c</code>.
*
* @param c a config class
* @param configId a config id to use when getting the config
* @param source a {@link ConfigSource}
* @return an instance of a config class
*/
public static <T extends ConfigInstance> T getConfig(Class<T> c, String configId, ConfigSource source) {
ConfigGetter<T> getter = new ConfigGetter<T>(source, c);
return getter.getConfig(configId);
}
}
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