How to add or set query params in rest test step using groovy script

Answering my own question.

I have used below code to set query params to REST request.

String targetQueryString = "";
if (mockRequest.getHttpRequest().getQueryString() != null) {
    targetQueryString = mockRequest.getHttpRequest().getQueryString();
}
Project project = new WsdlProject();
RestServiceConfig serviceConfig = RestServiceConfig.Factory.newInstance();
RestService service = new RestService((WsdlProject) project, serviceConfig);
RestResourceConfig resourceConfig = RestResourceConfig.Factory.newInstance();
RestResource resource = new RestResource(service, resourceConfig);
RestMethodConfig methodConfig = RestMethodConfig.Factory.newInstance();
RestMethod restMethod = new RestMethod(resource, methodConfig);
RestRequestConfig requestConfig = RestRequestConfig.Factory.newInstance();
RestRequest restRequest = new RestRequest(restMethod, requestConfig, false);
if (targetQueryString.length() > 0) {
    for (String param : targetQueryString.split("&")) {
        restMethod.setPropertyValue(param.split("=")[0], param.split("=")[1]);
    }
}