反射代理 - 类加载器问题的可见性

发布于 2024-11-01 17:34:56 字数 936 浏览 0 评论 0原文

我正在尝试：
1) 从给定文件位置加载接口和实现类
2) 创建一个具有与接口匹配的反射的 Proxy 对象，并将所有调用定向到实现类

这稍后将用于使用 JUnit 进行测试。

问题：
但是，当我尝试创建代理对象时似乎遇到了问题。我收到异常：

java.lang.IllegalArgumentException: interface Testing.Testable is not visible from class loader
...at Core.ProxyFactory.createProxy(ProxyFactory.java:26)

有问题的行如下：

Object obj = Proxy.newProxyInstance(implementationClass.getClassLoader(), new Class[]{interfaceClass}, forwarder);

类加载方式正确吗？
我正在使用 URLClassLoader 加载所需的类。其片段如下：

URL url = new File(path).toURI().toURL();
URL[] urlList = {url};
// Create loader and load
ClassLoader classLoader = new URLClassLoader(urlList);
Class loadedClass = classLoader.loadClass (classname);
return loadedClass;

但是，这是正确的吗？对于每个类文件都会重复此片段，因此我相信每次创建新的类加载器时。这会导致我的问题吗？我该如何解决这个问题？

提前感谢您提供的任何帮助

原文

I'm attempting to:
1) Load an interface and implementation class from a given file location
2) Create a Proxy object with reflection that matches the interface, and directs all calls to the implementation class

This is later used for testing purposes using JUnit.

The Problem:
However, I seem to be having problems when I try to create the proxy object. I get the exception:

java.lang.IllegalArgumentException: interface Testing.Testable is not visible from class loader
...at Core.ProxyFactory.createProxy(ProxyFactory.java:26)

The line in question is as follows:

Object obj = Proxy.newProxyInstance(implementationClass.getClassLoader(), new Class[]{interfaceClass}, forwarder);

Class loading the right way?
I am loading the classes that I need using a URLClassLoader. The snippet for this is as follows:

URL url = new File(path).toURI().toURL();
URL[] urlList = {url};
// Create loader and load
ClassLoader classLoader = new URLClassLoader(urlList);
Class loadedClass = classLoader.loadClass (classname);
return loadedClass;

However, is this correct? This snippet gets repeated for each class file, and so I believe each time a new class loader is created. Could this be causing my problem? How can I resolve this?

Thanks in advance for any help you can give

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以往的大感动 2024-11-08 17:34:56

已解决...
我对我以错误的方式加载类的担忧是正确的。因为这些类相互依赖（例如，一个类使用另一个类），所以它们需要属于同一个类加载器，或其子类加载器。

这个问题可以通过将 URLClassLoader 的使用替换为来解决：

ClassLoader classLoader = new URLClassLoader(urlList);
Class[] classes = new Class[classNames.length];
for (int i = 0; i<classNames.length; i++) {
  classes[i] = classLoader.loadClass(classNames[i]);
}

这允许您使用相同的类加载器加载多个类，并且似乎可以解决问题！

Solved...
I was correct in my concerns that I was loading the classes in the wrong way. Because the classes depend on each other (e.g. one class uses another), they need to belong to the same classloader, or a child therefore of.

This problem can be solved by replacing use of the URLClassLoader with:

ClassLoader classLoader = new URLClassLoader(urlList);
Class[] classes = new Class[classNames.length];
for (int i = 0; i<classNames.length; i++) {
  classes[i] = classLoader.loadClass(classNames[i]);
}

This allows you to load multiple classes using the same classloader, and seems to solve the problem!

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