https://tomcat.apache.org/: Interface code to the native connector 
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package org.apache.tomcat.jni;


PoolCallback Interface

Author:Mladen Turk
Deprecated: The scope of the APR/Native Library will be reduced in Tomcat
             10.1.x onwards to only those components required to provide
             OpenSSL integration with the NIO and NIO2 connectors.
/** PoolCallback Interface
 *
 * @author Mladen Turk
 *
 * @deprecated  The scope of the APR/Native Library will be reduced in Tomcat
 *              10.1.x onwards to only those components required to provide
 *              OpenSSL integration with the NIO and NIO2 connectors.
 */
@Deprecated
public interface PoolCallback {

    
Called when the pool is destroyed or cleared

Returns:Function must return APR_SUCCESS
/**
     * Called when the pool is destroyed or cleared
     * @return Function must return APR_SUCCESS
     */
    public int callback();
}