Java，带有 Digester 解析器的 java.lang.reflect.InvocationTargetException
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/5110991/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Java, java.lang.reflect.InvocationTargetException with Digester parser
提问by aneuryzm
I've a Java app, working with Lucene and Apache commons Digester to parse a xml collection. After the first item is parsed, I get this error... What does it mean ?
我有一个 Java 应用程序，使用 Lucene 和 Apache commons Digester 来解析 xml 集合。解析第一个项目后，我收到此错误...这是什么意思？
Feb 24, 2011 5:53:16 PM org.apache.commons.digester.Digester endElement
SEVERE: End event threw exception
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.commons.beanutils.MethodUtils.invokeMethod(MethodUtils.java:216)
at org.apache.commons.digester.SetNextRule.end(SetNextRule.java:220)
at org.apache.commons.digester.Rule.end(Rule.java:257)
at org.apache.commons.digester.Digester.endElement(Digester.java:1345)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:601)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1782)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2938)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
at org.apache.commons.digester.Digester.parse(Digester.java:1871)
at CollectionIndexer.main(CollectionIndexer.java:103)
Caused by: java.lang.NullPointerException
at CollectionIndexer.addDocument(CollectionIndexer.java:41)
... 20 more
Exception in thread "main" java.lang.NullPointerException
at org.apache.commons.digester.Digester.createSAXException(Digester.java:3363)
at org.apache.commons.digester.Digester.createSAXException(Digester.java:3389)
at org.apache.commons.digester.Digester.endElement(Digester.java:1348)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:601)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1782)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2938)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
at org.apache.commons.digester.Digester.parse(Digester.java:1871)
at CollectionIndexer.main(CollectionIndexer.java:103)
Caused by: java.lang.NullPointerException
at CollectionIndexer.addDocument(CollectionIndexer.java:41)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.commons.beanutils.MethodUtils.invokeMethod(MethodUtils.java:216)
at org.apache.commons.digester.SetNextRule.end(SetNextRule.java:220)
at org.apache.commons.digester.Rule.end(Rule.java:257)
at org.apache.commons.digester.Digester.endElement(Digester.java:1345)
... 12 more
回答by skaffman
Looks pretty clear to me:
对我来说看起来很清楚：
Caused by: java.lang.NullPointerException
at CollectionIndexer.addDocument(CollectionIndexer.java:41)
Your problem is right there. You need to more defensive in your code to protect against null references.
你的问题就在那里。您需要在代码中采取更多防御措施以防止空引用。
P.S. It's very bad practice to put your code into the default package. You should always put classes into an explicit package.
PS 将您的代码放入默认包中是非常糟糕的做法。您应该始终将类放入显式包中。
回答by Tomasz Nurkiewicz
Is CollectionIndexeryour own class? It seems like it throws NullPointerExceptionon line 41. It is invoked by SAX event parser, hence being wrapped by InvocationTargetException.
是CollectionIndexer你自己的课吗？它似乎NullPointerException在第 41 行抛出。它由 SAX 事件解析器调用，因此被InvocationTargetException.
BTW: JVM prints stack traces starting from the outermost one, displaying the innermost exception at the end. But since the innermost exception is thrown at the beginning, it is almost always the most interesting one. So as a rule of thumb: always look at the last caused byclause in exception stack trace, as it is typically the most interesting.
顺便说一句：JVM 从最外面的一个开始打印堆栈跟踪，最后显示最里面的异常。但是由于最内层的异常是一开始就抛出的，所以它几乎总是最有趣的。所以作为一个经验法则：总是查看caused by异常堆栈跟踪中的最后一个子句，因为它通常是最有趣的。
