import org.ovirt.engine.sdk.Api;
import org.ovirt.engine.sdk.decorators.Host;
import org.ovirt.engine.sdk.entities.PowerManagement;


public class debugRemove {
        private static final String URL = "https://ilia-rhevm.qa.lab.tlv.redhat.com:443/api";

    public static void main(String[] args) throws Exception {
        Api api = new Api(URL, "admin@internal", "123456", true);
        Host hst = (Host) api.getHosts().list().get(0);
        PowerManagement pm = new PowerManagement();
        pm.setType("apc");
        Boolean bl = new Boolean("true");
        pm.setEnabled(bl);
        hst.setPowerManagement(pm);
        hst.update();
        api.close();
    }
}

raises next exception:
Exception in thread "main" 
code  : 400
reason: Bad Request
detail: may not be null
	at org.ovirt.engine.sdk.web.HttpProxy.execute(HttpProxy.java:118)
	at org.ovirt.engine.sdk.web.HttpProxyBroker.update(HttpProxyBroker.java:104)
	at org.ovirt.engine.sdk.decorators.Host.update(Host.java:390)
	at debugRemove.main(debugRemove.java:17)