com.netflix.eventbus.spi.SubscriberConfigProvider Maven / Gradle / Ivy

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package com.netflix.eventbus.spi;

import javax.annotation.Nullable;

/**
 * A contract to handle dynamic subscriber configuration. Since, any configuration provided by {@link Subscribe}
 * annotation is inherently compile-time & constant, in cases where the configurations are to be taken from a property
 * file for instance, a subscriber must implement this interface and provide dynamic configurations. 

 * These configurations will be used once & only once by eventbus at the time the subscriber is registered. 

 * All the subscriber methods in a class can be configured using this provider, by pinning a configuration to a key
 * which is attached to a subscriber method by the property {@link com.netflix.eventbus.spi.Subscribe#name()}. 

 * For a subscriber that implements interface, for any subscriber method, eventbus follows the following order to get
 * the configuration for that subscriber method:
 * 
 Calls {@link SubscriberConfigProvider#getConfigForName(String)} with the name as specified by
 {@link com.netflix.eventbus.spi.Subscribe#name()}
 If the configuration returned above is not null then uses this configuration for any field.
 If the configuration returned above is null then uses any configuration provided by the annotation
 as is.
 
 *
 * @author Nitesh Kant
 */
public interface SubscriberConfigProvider {

    /**
     * Returns the configuration for the passed subscriber name.
     *
     * @param subscriberName Name of the subscriber.
     *
     * @return The configuration or null if the configuration for that subscriber is not supplied by this
     * provider.
     */
    @Nullable
    SubscriberConfig getConfigForName(String subscriberName);

    /**
     * Configuration for a subscriber. Any property that can be configured by {@link Subscribe} can also be configured
     * here.
     */
    interface SubscriberConfig {

        Subscribe.BatchingStrategy getBatchingStrategy();

        int getBatchAge();

        int getBatchSize();

        int getQueueSize();

        boolean syncIfAllowed();
    }
}