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Kiwi is a utility library. We really like Google's Guava, and also use Apache Commons. But if they don't have something we need, and we think it is useful, this is where we put it.

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package org.kiwiproject.dropwizard.lifecycle;

import com.google.common.util.concurrent.Runnables;
import io.dropwizard.lifecycle.Managed;
import io.dropwizard.lifecycle.setup.LifecycleEnvironment;
import lombok.experimental.UtilityClass;

/**
 * Provides utilities related to the Dropwizard lifecycle.
 */
@UtilityClass
public class KiwiDropwizardLifecycles {

    /**
     * Creates a Dropwizard {@link Managed} whose start action is {@code startAction} and whose stop action
     * is {@code stopAction}, and attaches it to the given Dropwizard {@code lifecycle}.
     * 
     * Useful when you have some external object that has start and stop methods, but you don't want to clutter your
     * code by creating an anonymous inner class just to specify the start and stop actions. For example, if you have
     * an ActiveMQ {@code PooledConnectionFactory} (which has {@code start} and {@code stop} methods) you can
     * call this method:
     * 

     * {@code KiwiDropwizardLifecycles.manage(lifecycle, () -> factory.start(), () -> factory.stop());}
     * 

     * To make the code cleaner, use method references:
     * 

     * {@code KiwiDropwizardLifecycles.manage(lifecycle, factory::start, factory::stop);}
     *
     * @param lifecycle   the lifecycle to manage
     * @param startAction the action to run when Dropwizard starts the application
     * @param stopAction  the action to run when Dropwizard stops the application
     */
    public static void manage(LifecycleEnvironment lifecycle, Runnable startAction, Runnable stopAction) {
        lifecycle.manage(new Managed() {
            @Override
            public void start() {
                startAction.run();
            }

            @Override
            public void stop() {
                stopAction.run();
            }
        });
    }

    /**
     * Creates a Dropwizard {@link Managed} whose start action is {@code startAction},
     * and attaches it to the given Dropwizard {@code lifecycle}.
     * 

     * Useful when you have some external object that has a start method, but you don't want to clutter your
     * code by creating an anonymous inner class just to specify the start action. For example, if you have
     * a monitoring class that needs to start when the application starts, you can ensure that it happens
     * using code like:
     * 

     * {@code KiwiDropwizardLifecycles.manage(lifecycle, () -> monitor.start());}
     * 

     * To make the code cleaner, use method references:
     * 

     * {@code KiwiDropwizardLifecycles.manage(lifecycle, monitor::start);}
     *
     * @param lifecycle   the lifecycle to manage
     * @param startAction the action to run when Dropwizard starts the application
     */
    public static void manageOnlyStart(LifecycleEnvironment lifecycle, Runnable startAction) {
        manage(lifecycle, startAction, Runnables.doNothing());
    }

    /**
     * Creates a Dropwizard {@link Managed} whose stop action is {@code stopAction},
     * and attaches it to the given Dropwizard {@code lifecycle}.
     * 

     * Useful when you have some external object that has a stop method, but you don't want to clutter your
     * code by creating an anonymous inner class just to specify the stop action. For example, if you have
     * an HTTP {@code Client} class that needs to stop when the application shuts down to ensure resources
     * are properly closed, you can ensure that happens using code like:
     * 

     * {@code KiwiDropwizardLifecycles.manage(lifecycle, () -> client.close());}
     * 

     * To make the code cleaner, use method references:
     * 
     * {@code KiwiDropwizardLifecycles.manage(lifecycle, client::close);}
     *
     * @param lifecycle   the lifecycle to manage
     * @param stopAction  the action to run when Dropwizard stops the application
     */
    public static void manageOnlyStop(LifecycleEnvironment lifecycle, Runnable stopAction) {
        manage(lifecycle, Runnables.doNothing(), stopAction);
    }
}