如何使用libvirt java api启动来宾域 .

我有一台客机,目前已关机 . 如何开机

那台机器使用libvirt java api .Below是我的代码

@RequestMapping(value = "/power/{vmName}", produces = { "application/json" }, method = RequestMethod.PUT)
    public @ResponseBody ResponseEntity updatePower(HttpServletRequest request, @PathVariable("vmName") String vmName) throws LibvirtException {
        ResponseEntity resp = null;

        Connect conn = Connection.getConnection();

        Domain machine=conn.domainLookupByName(vmName);

        if(machine.isActive()==1){
            machine.shutdown();
        }else{
            //I need to start my guest domain here if its inactive.
        }


        return resp;
    }