我一直在寻找解决这个问题的方法，但似乎很困难。我有一个 appengine 项目与处理注册的 servlet 一起使用。当我尝试调用这个 servlet 时，我有以下日志报告：
012-04-19 10:31:06.816 /register 500 90ms 0kb Apache-HttpClient/UNAVAILABLE (java 1.4)
ip - gecodroidtest [19/Apr/2012:10:31:06 -0700] "POST /register HTTP/1.1" 500 0 - "Apache-HttpClient/UNAVAILABLE (java 1.4)" "cloudnotifyit.appspot.com" ms=90 cpu_ms=58 api_cpu_ms=0 cpm_usd=0.001738 instance=00c61b117c772731eb45290bfcb07750c0505f
W 2012-04-19 10:31:06.794
com.cloudnotify.server.servlet.RequestInfo processRequest: xxxxxxxxxxxx@xxxx //just for me
W 2012-04-19 10:31:06.810
Error for /register
java.lang.NoClassDefFoundError: org/w3c/dom/ElementTraversal
at com.google.appengine.runtime.Request.process-240c2ffe1bf8ddba(Request.java)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at org.apache.xerces.parsers.AbstractDOMParser.startDocument(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.startDocument(Unknown Source)
at org.apache.xerces.impl.XMLDocumentScannerImpl.startEntity(Unknown Source)
at org.apache.xerces.impl.XMLVersionDetector.startDocumentParsing(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)
at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source)
at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:121)
at javax.jdo.JDOHelper.readNamedPMFProperties(JDOHelper.java:1407)
at javax.jdo.JDOHelper.getNamedPMFProperties(JDOHelper.java:1286)
at javax.jdo.JDOHelper.getPropertiesFromJdoconfig(JDOHelper.java:1232)
at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:1079)
at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:914)
at com.cloudnotify.server.c2dm.C2DMessaging.getPMF(C2DMessaging.java:103)
at com.cloudnotify.server.servlet.RequestInfo.initDevices(RequestInfo.java:225)
at com.cloudnotify.server.servlet.RequestInfo.processRequest(RequestInfo.java:183)
at com.cloudnotify.server.servlet.RegisterServlet.doPost(RegisterServlet.java:100)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.lang.ClassNotFoundException: org.w3c.dom.ElementTraversal
at com.google.appengine.runtime.Request.process-240c2ffe1bf8ddba(Request.java)
... 44 more
C 2012-04-19 10:31:06.812
Uncaught exception from servlet
java.lang.NoClassDefFoundError: org/w3c/dom/ElementTraversal
at com.google.appengine.runtime.Request.process-240c2ffe1bf8ddba(Request.java)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at org.apache.xerces.parsers.AbstractDOMParser.startDocument(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.startDocument(Unknown Source)
at org.apache.xerces.impl.XMLDocumentScannerImpl.startEntity(Unknown Source)
at org.apache.xerces.impl.XMLVersionDetector.startDocumentParsing(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)
at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source)
at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:121)
at javax.jdo.JDOHelper.readNamedPMFProperties(JDOHelper.java:1407)
at javax.jdo.JDOHelper.getNamedPMFProperties(JDOHelper.java:1286)
at javax.jdo.JDOHelper.getPropertiesFromJdoconfig(JDOHelper.java:1232)
at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:1079)
at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:914)
at com.cloudnotify.server.c2dm.C2DMessaging.getPMF(C2DMessaging.java:103)
at com.cloudnotify.server.servlet.RequestInfo.initDevices(RequestInfo.java:225)
at com.cloudnotify.server.servlet.RequestInfo.processRequest(RequestInfo.java:183)
at com.cloudnotify.server.servlet.RegisterServlet.doPost(RegisterServlet.java:100)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.lang.ClassNotFoundException: org.w3c.dom.ElementTraversal
at com.google.appengine.runtime.Request.process-240c2ffe1bf8ddba(Request.java)
... 44 more
Thanks all
在 pom.xml 中，将“xml-apis”依赖项设置为版本 1.4.01：
<dependency>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
<version>1.4.01</version>
</dependency>
如果不使用maven，您可以手动添加xml-apis库，版本1.4.01。您将在 xml-commons 二进制包中找到这些 jar，名为“XML CommonsExternal 1.4.01”，您可以在此处下载：http://xerces.apache.org/mirrors.cgi http://xerces.apache.org/mirrors.cgi.
最后，使用此版本的库编译并执行您的 java 应用程序/项目。
xml-apis 库的 1.4.01 版本包含所需的 ElementTraversal 类。其他版本如2.0.0、1.0.0等不包含它，应用程序在编译时失败。
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