我将一个Java库打包为JAR,当我试图从它调用方法时,它抛出许多Java .lang. incompatibleclasschangeerror。这些错误似乎是随机出现的。什么样的问题会导致这个错误?
当前回答
I have also discovered that, when using JNI, invoking a Java method from C++, if you pass parameters to the invoked Java method in the wrong order, you will get this error when you attempt to use the parameters inside the called method (because they won't be the right type). I was initially taken aback that JNI does not do this checking for you as part of the class signature checking when you invoke the method, but I assume they don't do this kind of checking because you may be passing polymorphic parameters and they have to assume you know what you are doing.
示例c++ JNI代码:
void invokeFooDoSomething() {
jobject javaFred = FredFactory::getFred(); // Get a Fred jobject
jobject javaFoo = FooFactory::getFoo(); // Get a Foo jobject
jobject javaBar = FooFactory::getBar(); // Get a Bar jobject
jmethodID methodID = getDoSomethingMethodId() // Get the JNI Method ID
jniEnv->CallVoidMethod(javaFoo,
methodID,
javaFred, // Woops! I switched the Fred and Bar parameters!
javaBar);
// << Insert error handling code here to discover the JNI Exception >>
// ... This is where the IncompatibleClassChangeError will show up.
}
Java代码示例:
class Bar { ... }
class Fred {
public int size() { ... }
}
class Foo {
public void doSomething(Fred aFred, Bar anotherObject) {
if (name.size() > 0) { // Will throw a cryptic java.lang.IncompatibleClassChangeError
// Do some stuff...
}
}
}
其他回答
In my case, I ran into this error this way. pom.xml of my project defined two dependencies A and B. And both A and B defined dependency on same artifact (call it C) but different versions of it (C.1 and C.2). When this happens, for each class in C maven can only select one version of the class from the two versions (while building an uber-jar). It will select the "nearest" version based on its dependency mediation rules and will output a warning "We have a duplicate class..." If a method/class signature changes between the versions, it can cause a java.lang.IncompatibleClassChangeError exception if the incorrect version is used at runtime.
高级:如果A必须使用C的v1, B必须使用C的v2,那么我们必须在A和B的poms中重新定位C,以避免类冲突(我们有一个重复类警告),当构建依赖于A和B的最终项目时。
我遇到了同样的问题,后来我发现我是在Java版本1.4上运行应用程序,而应用程序是在版本6上编译的。
实际上,这是因为有一个重复的库,一个位于类路径中,另一个包含在位于类路径中的jar文件中。
I have a web application that deploys perfectly fine on my local machine's tomcat(8.0.20). However, when I put it into the qa environment (tomcat - 8.0.20), it kept on giving me the IncompatibleClassChangeError and it was complaining that I was extending on an interface. This interface was changed to an abstract class. And I compiled the parent and child classes and still I kept on getting the same issue. Finally, I wanted to debug, so, I changed the version on the parent to x.0.1-SNAPSHOT and then compiled everything and now it is working. If someone is still hitting the problem after following the answers given here, please make sure the versions in your pom.xml are also correct. Change the versions to see if that works. If so, then fix the version problem.
这意味着您已经对库进行了一些不兼容的二进制更改,而无需重新编译客户端代码。Java语言规范§13详细描述了所有这些更改,最突出的是将非静态的非私有字段/方法更改为静态或反之亦然。
根据新的库重新编译客户端代码,应该就可以开始了。
更新:如果你发布了一个公共库,你应该尽可能避免做出不兼容的二进制更改,以保持所谓的“二进制向后兼容性”。单独更新依赖jar在理想情况下不会破坏应用程序或构建。如果你不得不打破二进制向后兼容性,建议增加主版本号(例如从1.x。Y到2.0.0),然后发布更改。
我的答案,我相信,将是Intellij具体。
我重新构建干净,甚至手动删除“out”和“target”dirs。Intellij有一个“无效缓存并重新启动”,它有时会清除奇怪的错误。这次没有成功。依赖版本在项目设置->模块菜单中看起来都是正确的。
最后的答案是从本地maven repo中手动删除我的问题依赖项。旧版本的bouncycastle是罪魁祸首(我知道我只是改变了版本,这就是问题所在),尽管旧版本没有出现在正在建造的东西中,但它解决了我的问题。我使用的是intellij版本14,然后在此过程中升级到15。
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