相关疑难解决方法(0)

以下代码(通过JNLP API检索Java Web Start客户端应用程序的基本URL)在Java 8中工作,但在(模块化)Java 9运行时中执行时失败:

Class<?> mclass = Class.forName("javax.jnlp.ServiceManager");
Method lookup = mclass.getMethod("lookup", new Class[]{String.class});
Object basicSvc = lookup.invoke(null, new Object[{"javax.jnlp.BasicService"});
Class<?> sclass = basicSvc.getClass();
Method getCodeBase = sclass.getMethod("getCodeBase", (Class[])null);
URL codebase = (URL)getCodeBase.invoke(basicSvc, (Object[])null); // throws

结果是

java.lang.IllegalAccessException: class app.App cannot access class
  com.sun.jnlp.BasicServiceImpl (in module jdk.javaws) because module
  jdk.javaws does not export com.sun.jnlp to unnamed module @7202a0fa
    at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException
    at java.base/java.lang.reflect.AccessibleObject.checkAccess
    at java.base/java.lang.reflect.Method.invoke
    at app.App.init

怎么解决这个问题？