OSGi noClassDefFound for java.nio.files.FileSystems $ DefaultFileSystemHolder [英] OSGi noClassDefFound for java.nio.files.FileSystems$DefaultFileSystemHolder
问题描述
在我们的应用程序中，我们使用ini文件来配置我们的OSGi应用程序。现在我考虑添加一个WatchService来检测更改并在必要时重新加载修改后的文件。
in our application, we're using ini files for the configuration of our OSGi apps. Now I thought about adding a WatchService to detect changes and reload the modified file if necessary.
到目前为止我找到了多个教程。其中大多数都是相似的，并产生如下内容：
http://java.dzone.com/news/how-watch-file-system-changes 。我这样采用它：
I found multiple tutorials so far. Most of them are similar and result in something like the following: http://java.dzone.com/news/how-watch-file-system-changes. I adopted it like this:
36: public Ini(final File file) throws IOException {
if (!file.exists()) {
throw new IOException("Ini-File does not exist.");
} else if (!file.canRead()) {
40: throw new IOException("Ini-File is not readable.");
}
iniFile = file;
FileSystem fileSystem = FileSystems.getFileSystem(file.toURI());
45: Path test = fileSystem.getPath(file.getAbsolutePath());
Path ini = FileSystems.getDefault().getPath(file.getParent(), file.getName());
Logger.debug(ini.toString());
readIni(ini);
50: service = FileSystems.getDefault().newWatchService();
file.getParentFile().toPath().register(service, ENTRY_MODIFY);
Thread watcher = new Thread(() -> {
// noinspection InfiniteLoopStatement
55: while (true) {
WatchKey key = null;
try {
key = service.take();
for (WatchEvent<?> event : key.pollEvents()) {
60: Logger.debug("event received");
if (event.kind() != ENTRY_MODIFY) {
continue;
}
WatchEvent<Path> ev = (WatchEvent<Path>) event;
65:
File filename = ev.context().toFile();
if (filename.getAbsolutePath().equals(iniFile.getAbsolutePath())) {
Logger.debug(filename.getName() + " has changed");
70: config = new HashMap<>();
try {
readIni(filename.toPath());
} catch(IOException e) {
Logger.warning(e);
75: }
}
}
} catch (Exception e) {
Logger.warning(e);
80: }
if (key != null)
key.reset();
}
});
85:
watcher.start();
}
创建新实例时，我首先检查文件是否存在。在此之后，我想创建一个WatchService来分析这个配置文件（起初只有这个。后来我将为所有加载的文件更改为1 WatchService。）
When creating a new instance, I first check whether the file exist or not. After this, I want to create a WatchService profiling this config file (at first only this one. Later I will change to 1 WatchService for all loaded files).
几行（44-46）以不同的方式做同样的事情。他们都没有工作。
There are several lines (44 - 46) doing the same in different ways. None of them worked.
现在当我创建这样的Ini文件时，felix告诉我以下内容：
Now when I create an Ini file like this, felix tells me the following:
[ERROR] : java.lang.NoClassDefFoundError: Could not initialize class java.nio.file.FileSystems$DefaultFileSystemHolder
java.lang.IllegalStateException: java.lang.NoClassDefFoundError: Could not initialize class java.nio.file.FileSystems$DefaultFileSystemHolder
at org.apache.felix.ipojo.handlers.lifecycle.callback.LifecycleCallbackHandler.__M_stateChanged(LifecycleCallbackHandler.java:171)
at org.apache.felix.ipojo.handlers.lifecycle.callback.LifecycleCallbackHandler.stateChanged(LifecycleCallbackHandler.java)
at org.apache.felix.ipojo.InstanceManager.setState(InstanceManager.java:560)
at org.apache.felix.ipojo.InstanceManager.start(InstanceManager.java:440)
at org.apache.felix.ipojo.ComponentFactory.createInstance(ComponentFactory.java:179)
at org.apache.felix.ipojo.IPojoFactory.createComponentInstance(IPojoFactory.java:319)
at org.apache.felix.ipojo.IPojoFactory.createComponentInstance(IPojoFactory.java:240)
at org.apache.felix.ipojo.extender.internal.linker.ManagedType$InstanceSupport$1.call(ManagedType.java:312)
at org.apache.felix.ipojo.extender.internal.linker.ManagedType$InstanceSupport$1.call(ManagedType.java:306)
at org.apache.felix.ipojo.extender.internal.queue.JobInfoCallable.call(JobInfoCallable.java:114)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoClassDefFoundError: Could not initialize class java.nio.file.FileSystems$DefaultFileSystemHolder
at java.nio.file.FileSystems.getDefault(FileSystems.java:176)
at java.nio.file.spi.FileSystemProvider.installedProviders(FileSystemProvider.java:156)
at java.nio.file.FileSystems.getFileSystem(FileSystems.java:219)
at df.core.config.internal.Ini.<init>(Ini.java:44)
at df.core.config.internal.ConfigImpl.__M_addConfig(ConfigImpl.java:180)
at df.core.config.internal.ConfigImpl.addConfig(ConfigImpl.java)
at df.core.config.api.Config$$Proxy.addConfig(Unknown Source)
at df.playground.IniTest.__M_validate(IniTest.java:24)
at df.playground.IniTest.validate(IniTest.java)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.apache.felix.ipojo.util.Callback.call(Callback.java:237)
at org.apache.felix.ipojo.util.Callback.call(Callback.java:193)
at org.apache.felix.ipojo.handlers.lifecycle.callback.LifecycleCallback.call(LifecycleCallback.java:86)
at org.apache.felix.ipojo.handlers.lifecycle.callback.LifecycleCallbackHandler.__M_stateChanged(LifecycleCallbackHandler.java:162)
... 13 more
这说明第44行搜索文件的fileSystem对象。我做错了什么，因为我的代码找不到DefaultFileSystemHolder？这是一个java内部类，所以我不需要在我的MANIFEST.MF中使用import语句，对吗？
This states me to line 44 which searches for the fileSystem object for the file. Am I doing something wrong because my Code does not find the DefaultFileSystemHolder? It's a java internal class so I shouldn't need an import statement in my MANIFEST.MF, right?
它使用Apache Felix 4.4.1和Oracle在Ubuntu 14.04上运行Java 8并使用Maven构建。
It's running on Ubuntu 14.04 using Apache Felix 4.4.1 and Oracle Java 8 and build with Maven.
提前致谢
推荐答案
tl; dr
将以下配置添加到Felix：
tl;dr
Add the following configuration to Felix:
org.osgi.framework.bootdelegation=sun.nio.*
说明：
Oracle JDK中的 FileSystems 实现使用内部类 sun.nio.fs.DefaultFileSystemProvider 。这是JDK实现的一个好奇心，因为它期望从任何类加载器中看到一些内部类，例如这个类。在OSGi中，所有bundle始终可见的唯一类是以 java。开头的类，例如 java.lang.String 等。
Explanation:
The FileSystems implementation in the Oracle JDK uses an internal class sun.nio.fs.DefaultFileSystemProvider. This is a curiosity of the JDK implementation, as it expects some internal classes such as this one to be visible from any classloader. In OSGi, the only classes that are always visible to all bundles are those beginning with java., such as java.lang.String etc.
bootdelegation配置允许我们扩展一组始终可见的包。它适用于这种情况，即JVM内部类。有时，它对于运行已经过检测的代码也很有用，例如用于覆盖或分析。它不是用于从JDK公开其他API的通用设置。
The bootdelegation config allows us to extend the set of always-visible packages. It is intended for exactly this scenario, i.e. for JVM internal classes. Sometimes it is also useful for running code that has been instrumented, e.g. for coverage or profiling. It is NOT a general purpose setting for exposing additional API from the JDK.
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