gistfile1.java

public interface ThreadSetupActionFactory<C> {
    ThreadSetupAction createThreadSetupAction(C context);
}


public class LazyThreadSetupAction<C> implements ThreadSetupAction {

    private static final Handle EMPTY_HANDLE = new Handle() {
        @Override
        public void tearDown() {
        }
    };

    private final C context;
    private final Value<ThreadSetupActionFactory<C>> factory;

    private volatile ThreadSetupAction action;

    public LazyThreadSetupAction(Value<ThreadSetupActionFactory<C>> factory, C context) {
        this.factory = factory;
        this.context = context;
    }

    @Override
    public Handle setup(HttpServerExchange exchange) {
        // This is first called with a null exchange during DeploymentManager.deploy(...)
        if (exchange == null) {
            if (this.action == null) {
                this.action = this.factory.getValue().createThreadSetupAction(this.context);
            }
            return EMPTY_HANDLE;
        }
        if (this.action == null) {
            throw new IllegalStateException();
        }
        return this.action.setup(exchange);
    }
}