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

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。

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。

另一种可能出现此错误的情况是Emma Code Coverage。

这发生在将Object分配给接口时。我猜这与对象被检测和不再二进制兼容有关。

http://sourceforge.net/tracker/?func=detail&aid=3178921&group_id=177969&atid=883351

幸运的是,这个问题在Cobertura中没有发生,所以我在pom.xml的报告插件中添加了Cobertura -maven-plugin

由于某种原因,当使用JNI并在调用Call*Method()时传递jclass参数而不是jobject时,也会抛出相同的异常。

这与《食人魔诗篇》第33篇中的回答相似。

void example(JNIEnv *env, jobject inJavaList) {
    jclass class_List = env->FindClass("java/util/List");

    jmethodID method_size = env->GetMethodID(class_List, "size", "()I");
    long size = env->CallIntMethod(class_List, method_size); // should be passing 'inJavaList' instead of 'class_List'

    std::cout << "LIST SIZE " << size << std::endl;
}

我知道在被问到这个问题5年后再回答这个问题有点晚了,但这是搜索java.lang.IncompatibleClassChangeError时最热门的问题之一,所以我想记录这个特殊情况。

如果你从事android开发。然后给一个尝试重建选项可能是为你修复。

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...
        }
    }
}