我正在开发一个 GWT 应用程序来从 Freebase 获取查询结果。现在我在我的服务实现类中使用以下代码。
import com.freebase.api.Freebase;
import com.freebase.json.JSON;
import com.google.tracker.client.FreebaseService;
import com.google.tracker.client.freebaseapi.Freebase;
import com.google.tracker.client.freebasejson.JSON;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;
public class FreebaseServiceImpl extends RemoteServiceServlet implements FreebaseService{
public String getDirectorName() throws IllegalArgumentException{
Freebase freebase = Freebase.getFreebase();
String query_str = "{" +
"'id': null," +
"'type': '/film/film'," +
"'name': 'Blade Runner'," +
"'directed_by': [{" +
"'id': null," +
"'name': null" +
"}]" +
"}".replace('\'', '"');
JSON query = new JSON(query_str);
JSON result = freebase.mqlread(query);
@SuppressWarnings("unused")
String director = result.get("result").get("directed_by").get(0).get("name").string();
return director;
}
}
我在运行应用程序时收到以下错误:
500 服务器调用失败;有关详细信息,请参阅服务器日志。
这些可能的原因是什么?