本文介绍了Java转换/类加载器问题的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
这是问题的简化版本:
SomeClass c = (SomeClass) obj.getSomeClassParent()
不总是,但有时会触发异常
not always but it happens sometimes to trigger exception
org.somepackage.SomeClass can't be cast to org.somepackage.SomeClass
这是怎么可能的?我想它有一些事实与JAI imageio是本机lib,但中继这怎么可能发生?我可能错过了什么,但什么?
How is this possible ? I suppose it has something to do with the fact that JAI imageio is native lib, but relay how can this happen ? I'm probably missing something but what ?
I'm using JAI imageio version 1.1
dcm4che 2.0.21 DICOM lib
以下是原始代码
ImageInputStream iis = ImageIO.createImageInputStream(src);
Iterator<ImageReader> iter = ImageIO.getImageReadersByFormatName("DICOM");
ImageReader reader = iter.next();
DicomImageReadParam param = (DicomImageReadParam) reader.getDefaultReadParam();
原始异常
org.dcm4che2.imageio.plugins.dcm.DicomImageReadParam can't be cast to
org.dcm4che2.imageio.plugins.dcm.DicomImageReadParam
推荐答案
我认为如果
- a
SomeClass
实例从ClassLoader X加载(因此它的类是CL X的SomeClass
或者让我们调用它: code> CL(X).SomeClass ) - ,但它是在不同的类加载器。例如。当前Threads类加载器是Y,因此
SomeClass
实际上是CL(Y).SomeClass
- a
SomeClass
instance was loaded from ClassLoader X (so its class isSomeClass
of CL X or let's call it:CL(X).SomeClass
) - but it is being cast in a different class loader. E.g. the current Threads class loader is Y so
SomeClass
is actuallyCL(Y).SomeClass
所以你有:
- 实例类=
CL(X).SomeClass
- class cast target =
li>
- instance class =
CL(X).SomeClass
- class cast target =
CL(Y).SomeClass
或者换句话说 - 不是同一个类 - 因此类转换异常。
Or in other words - not the same class - thus the class cast exception.
可能的副本: - 它也有一些好的建议。
Possible duplicate of: ClassCastException when casting to the same class - it has some good suggestions as well.
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