反射java模块层：模块层。控制器添加方法不起作用

Question

我使用的是Netbeans 12.5和java 16

在Java模块化项目中，我有两个模块

Modular-Testing(/*The Project Name*/)
|
|----Consumer(/*Module Name*/)
|    |
     |--classes(/*Folder Name*/)
        |
        |--main(/*package name*/)
           |
           |--CustomModuleTest.java(Main Class)    


     
|--Test_Module_A(/*Module Name*/)
    |
    |--classes(/*Folder Name*/)
        |
        |--package_a(/*package name*/)
           |
           |--ClassA.java  

自定义模块测试。爪哇

public static void main(String[] args)throws Exception
{
   Path baseDir=Path.of("C:/Users/Home/Documents/NetBeansProjects/Netbeans/Modular-Testing/build/modules/");
 
   //Create the configuration for these two modules with boot-layer configuration as it's parent
   Configuration level1=Configuration.resolve
   (
     ModuleFinder.of(baseDir.resolve("Consumer"),baseDir.resolve("Test_Module_A"))
    ,List.of(ModuleLayer.boot().configuration())
    ,ModuleFinder.of()
    ,List.of("Consumer","Test_Module_A")
   );   

   //create the module layer with only one system class loader and boot layer as parent
   ModuleLayer.Controller layer1=ModuleLayer.defineModulesWithOneLoader
   (
     level1
    ,List.of(ModuleLayer.boot())
    ,ClassLoader.getSystemClassLoader()
   ); 
   
   //this is the main purpose of this test. I want to call ClassA.callMe() via reflection after i have dynamically acheived the permissions for it by first
   //Making Consumer Module read(requires) Test_Module_A
   //Making Test_Module_A open it's package(package_a) to Consumer
   //With this consumer should have full reflective access to Test_Module_A(or that's what i had hoped but it didn't work)

                          //Require(Read)
   //Make Module Consumer--------------->Test_Module_A 
   layer1.addReads
   (
     layer1.layer().findModule("Consumer").get()
    ,layer1.layer().findModule("Test_Module_A").get()
   ); 
                                 //Open package_a
   //Make Module Test_Module_A-------------------->Consumer 
   layer1.addOpens
   (
    layer1.layer().findModule("Test_Module_A").get()
   ,"package_a"
   ,layer1.layer().findModule("Consumer").get()
   ); 
   
   //Do the actual Test
   Class targetClass=layer1.layer().findLoader("Test_Module_A").loadClass("package_a.ClassA");
   Method method=targetClass.getDeclaredMethod("callMe");
   method.trySetAccessible();
   method.invoke(null);  //<---------Crashes Here(It's a static method so no object reference)
}

ClassA什么都不做

package package_a;

public class ClassA 
{
  private static void callMe()
  {
   System.out.println("Hooray You Called Me Using ModuleLayers!!!");
  }
}

消费者和消费者的模块信息；测试模块A为空

module Consumer{}
module Test_Module_A{}

这两个模块的模块信息都是空的，因为我想使用ModuleLayer.Controller动态添加打开/导出

该类的定位没有任何问题。使用trySetAccessible（）使该方法可访问，但我一调用invoke就会出现此错误

Exception in thread "main" java.lang.IllegalAccessException: class main.CustomModuleTest (in module Consumer) cannot access class package_a.ClassA (in module Test_Module_A) because module Test_Module_A does not export package_a to module Consumer
    at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:385)
    at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:687)
    at java.base/java.lang.reflect.Method.invoke(Method.java:559)

该测试从CustomModuleTest运行。消费者模块内部的java主方法 addReads&；这个方法要么不起作用，要么就是我用错了

有什么想法吗

Answer 1

您正在创建一个包含两个模块的新模块层，并建立其中一个模块对另一个模块的访问。但是，您实际上希望为当前运行的main方法建立对这些模块之一的访问权限

当前运行的main方法不能是它刚刚创建的新模块层的一部分。假设是标准的启动程序设置，它属于Controller模块，由系统类加载程序作为启动层的一部分加载

因此，您不必在新层中授予对同名新模块的访问权限，而必须更改代码以授予对已加载的Controller模块的访问权限。由于新模块层的新Controller模块没有任何用途，因此可以将其从层配置中删除

public static void main(String[] args) throws Exception {
   Path baseDir = Path.of(
     "C:/Users/Home/Documents/NetBeansProjects/Netbeans/Modular-Testing/build/modules/");

   // Create the configuration for the new module
   // with boot-layer configuration as it's parent
   Configuration level1=Configuration.resolve
   (
     ModuleFinder.of(baseDir.resolve("Test_Module_A")),
     List.of(ModuleLayer.boot().configuration()),
     ModuleFinder.of(), List.of("Test_Module_A")
   );

   //create the module layer with only one class loader and boot layer as parent
   var layer1Controller = ModuleLayer.defineModulesWithOneLoader(
     level1, List.of(ModuleLayer.boot()), ClassLoader.getSystemClassLoader()
   );
   var testModA = layer1Controller.layer().findModule("Test_Module_A").get();
   var myModule = CustomModuleTest.class.getModule();

   myModule.addReads(testModA); // add read edge

   layer1Controller.addOpens(testModA, "package_a", myModule); // open package_a

   //Do the actual Test
   Class<?> targetClass = testModA.getClassLoader().loadClass("package_a.ClassA");
   Method method = targetClass.getDeclaredMethod("callMe");
   method.setAccessible(true);
   method.invoke(null);
}