找不到http://www.w3.org/2001/XMLSchema的工厂

Question

我的以下代码有一些烦人的问题，在切换到Java 1.7之前还可以正常工作

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

从带有-Djaxp.debug = 1的Netbeans运行，将引发以下错误：

上面的代码片段是OSGI捆绑包的一部分

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

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

该工厂是“ 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）。

为什么会有这种差异？ 似乎有什么问题吗？

Answer 1

在JRE 7上适合我的工作：

SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = factory.newSchema(new SAXSource(new InputSource(new ByteArrayInputStream(xsd.getBytes()))));
Validator validator = schema.newValidator();

validator.validate(new SAXSource(new InputSource(new ByteArrayInputStream(xml.getBytes()))));
System.out.println("Validated !");

Answer 2

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：

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 。

这是GitHub项目，以获取更多详细信息。

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