//Invoca el método pre cierre de la VPOS Server REST

public static void main(String[] args) {
		OkHttpClient client = new OkHttpClient();

		MediaType mediaType = MediaType.parse("application/json");
		RequestBody body = RequestBody.create(mediaType, "{\r\n    \"accion\": \"precierre\"\r\n}");
		Request request = new Request.Builder()
		  .url("http://localhost:8085/vpos/metodo")
		  .post(body)
		  .addHeader("content-type", "application/json")
		  .addHeader("cache-control", "no-cache")
		  .build();

		try {
			Response response = client.newCall(request).execute();
			System.out.println(response.body().string());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}