找不到http://www.w3.org/2001/XMLSchema的工厂 [英] Unable to find a factory for http://www.w3.org/2001/XMLSchema

问题描述

我的以下代码有一些烦人的问题，在切换到Java 1.7之前一直可以正常工作

I'm having some annoying problems with the following code, that worked okay until switched to Java 1.7

import javax.xml.validation.SchemaFactory;
SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

使用-Djaxp.debug = 1从Netbeans运行，会引发以下错误:

Running from Netbeans with -Djaxp.debug=1, the following error is thrown:

上面的代码片段是OSGI软件包的一部分

The above snipped code is part of an OSGI bundle

JAXP: using thread context class loader (sun.misc.Launcher$AppClassLoader@5e3a78ad) for search
JAXP: Looking up system property 'javax.xml.validation.SchemaFactory:http://www.w3.org/2001/XMLSchema'
JAXP: The property is undefined.
JAXP: found null in $java.home/jaxp.properties
JAXP: no META-INF/services/javax.xml.validation.SchemaFactory file was found
JAXP: attempting to use the platform default XML Schema validator
JAXP: instanciating org.apache.xerces.jaxp.validation.XMLSchemaFactory
JAXP: failed to instanciate org.apache.xerces.jaxp.validation.XMLSchemaFactory
java.lang.ClassNotFoundException: org.apache.xerces.jaxp.validation.XMLSchemaFactory
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at javax.xml.validation.SchemaFactoryFinder.createInstance(Unknown Source)
at javax.xml.validation.SchemaFactoryFinder._newFactory(Unknown Source)
at javax.xml.validation.SchemaFactoryFinder.newFactory(Unknown Source)
at javax.xml.validation.SchemaFactory.newInstance(Unknown Source)
JAXP: unable to find a factory for http://www.w3.org/2001/XMLSchema
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: http://www.w3.org/2001/XMLSchema

我还制作了一个只有工厂实例的小型Java应用程序

I have also made a small Java app with only the factory instance

SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

工厂是"com.sun.org.apache.xerces.internal.jaxp.validation.XMLSchemaFactory" 的实例，而在我的捆绑包中，它试图实例化"org.apache. xerces.jaxp.validation.XMLSchemaFactory" (可能无法找到它).

The factory is instance of "com.sun.org.apache.xerces.internal.jaxp.validation.XMLSchemaFactory" while in my bundle it tries to instantiate "org.apache.xerces.jaxp.validation.XMLSchemaFactory" (and probably fails finding it).

为什么会有这种区别? 似乎是什么问题，有什么想法吗?

Why this difference ? What seems to be the problem, any ideea ?

推荐答案

我通过使用线程上下文类加载器(通常缩写为TCCL)来使其工作.这是代码:

I got this to work by using the Thread Context Class Loader (often abbreviated TCCL). Here's the code:

ClassLoader original = Thread.currentThread().getContextClassLoader();
try {
  Thread.currentThread().setContextClassLoader(ClassWithinYourBundle.class.getClassLoader());
  SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
} finally {
  Thread.currentThread().setContextClassLoader(original);
}

适当替换ClassWithinYourBundle.

这里是 GitHub项目.

有关TCCL的更多信息，请参见: https://articles.qos.ch/classloader.html

For more information on TCCL, see: https://articles.qos.ch/classloader.html

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