布局：
project.build.sourceEncoding，没有依赖项或插件！persistence.xml位于src/main/java/META-INF 下
执行Maven时导致以下错误 - 更新项目配置：
An internal error occurred during: "Updating Maven Configuration".
org.eclipse.jpt.core.resource.xml.JpaXmlResource cannot be cast to
org.eclipse.jpt.jpa.core.resource.xml.JpaXmlResource
在http://eclipsesrc.appspot.com/jsrcs/org.eclipse.jpt.core/src/org/eclipse/jpt/core/resource/xml/JpaXmlResource.java.html处提到了第一堂课，说明这个api仍处于开发阶段 我在http://wiki.eclipse.org/WTP_Provisional_API_Reduction/Indigo下找到了对第二节课的引用。
所以看起来我的一些插件中有一个版本存在冲突。但我对哪些人扯了扯。 我已经尝试过更新，但错误仍然存在。
已安装的版本：
Context and Dependency Injection Tools 1.2.0.v20120611-1827-H85-Final org.jboss.tools.cdi.feature.feature.group JBoss by Red Hat
Dojo Toolkit 1.7.2 (optional) 1.0.0.v20120530_1235 com.ibm.wdt.webtools.dojo.library.distributions.1.7.feature.feature.group IBM
Eclipse IDE for Java EE Developers 1.4.2.20120213-0813 epp.package.jee null
Forge Tools 1.0.0.v20120611-1732-H94-Final org.jboss.tools.forge.feature.feature.group JBoss by Red Hat
FreeMarker IDE 1.2.0.v20120611-1732-H94-Final org.jboss.ide.eclipse.freemarker.feature.feature.group JBoss by Red Hat
Hibernate Tools 3.4.0.v20120611-2017-H93-Final org.hibernate.eclipse.feature.feature.group JBoss by Red Hat
JavaHL 1.6.15 Win32 Binaries (Optional) 2.3.0.I20120316-1700 org.polarion.eclipse.team.svn.connector.javahl16.win32.feature.group Polarion Software
JavaHL 1.7.4 Win32 Binaries (Optional) 2.3.0.I20120316-1700 org.polarion.eclipse.team.svn.connector.javahl17.win32.feature.group Polarion Software
JBoss Archives Tools 3.2.1.v20120611-1725-H88-Final org.jboss.ide.eclipse.archives.feature.feature.group JBoss by Red Hat
JBoss Central 1.0.0.v20120612-0053-H99-Final org.jboss.tools.central.feature.feature.group JBoss by Red Hat
JBoss JAX-RS Tools 1.2.2.v20120611-1829-H137-Final org.jboss.tools.ws.jaxrs.feature.feature.group JBoss by Red Hat
JBoss Maven CDI Configurator 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.cdi.feature.feature.group JBoss by Red Hat
JBoss Maven Hibernate Configurator 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.hibernate.feature.feature.group JBoss by Red Hat
JBoss Maven Integration 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.feature.feature.group JBoss by Red Hat
JBoss Maven JAX-RS Configurator 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.jaxrs.feature.feature.group JBoss by Red Hat
JBoss Maven JPA Configurator 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.jpa.feature.feature.group JBoss by Red Hat
JBoss Maven JSF Configurator 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.jsf.feature.feature.group JBoss by Red Hat
JBoss Maven Portlet Configurator 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.portlet.feature.feature.group JBoss by Red Hat
JBoss Maven Project Examples 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.project.examples.feature.feature.group JBoss by Red Hat
JBoss Maven Seam Integration 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.seam.feature.feature.group JBoss by Red Hat
JBoss OpenShift Tools 2.3.0.v20120613-1951-H135-Final org.jboss.tools.openshift.express.feature.feature.group JBoss by Red Hat
JBoss Packaging Maven Configurators 1.3.0.v20120613-2141-H115-Final org.jboss.tools.maven.jbosspackaging.feature.feature.group JBoss by Red Hat
JBoss Portlet 1.2.0.v20120611-2357-H92-Final org.jboss.tools.portlet.feature.feature.group JBoss by Red Hat
JBoss Runtime AS Detector 1.3.0.v20120611-2354-H105-Final org.jboss.tools.runtime.as.detector.feature.feature.group JBoss by Red Hat
JBoss Runtime Detection Core 1.3.0.v20120611-2354-H105-Final org.jboss.tools.runtime.core.feature.feature.group JBoss by Red Hat
JBoss Runtime Seam Detector 1.3.0.v20120611-2354-H105-Final org.jboss.tools.runtime.seam.detector.feature.feature.group JBoss by Red Hat
JBoss Tools Common - Mylyn 3.3.0.v20120611-1634-H74-Final org.jboss.tools.common.mylyn.feature.feature.group JBoss by Red Hat
JBoss Tools Community Project Examples 1.2.1.v20120612-0012-H106-Final org.jboss.tools.community.project.examples.feature.feature.group JBoss by Red Hat
JBoss Tools EGit Integration (Experimental) 2.3.0.v20120613-1951-H135-Final org.jboss.tools.openshift.egit.integration.feature.feature.group JBoss by Red Hat
JBoss Tools Java Standard Tools 3.3.0.v20120611-1739-H85-Final org.jboss.tools.jst.feature.feature.group JBoss by Red Hat
JBoss Tools JDT Extensions 3.3.0.v20120611-1634-H74-Final org.jboss.tools.common.jdt.feature.feature.group JBoss by Red Hat
JBoss Tools JSF 3.3.0.v20120611-2148-H115-Final org.jboss.tools.jsf.feature.feature.group JBoss by Red Hat
JBoss Tools Mobile Browser Simulator 3.3.0.v20120611-1821-H102-Final org.jboss.tools.vpe.browsersim.feature.feature.group JBoss by Red Hat
JBoss Tools RichFaces 3.3.0.v20120611-2148-H115-Final org.jboss.tools.richfaces.feature.feature.group JBoss by Red Hat
JBoss Tools Usage Reporting 1.1.0.v20120611-1654-H68-Final org.jboss.tools.usage.feature.feature.group JBoss by Red Hat
JBoss Tools Visual Page Editor 3.3.0.v20120611-1821-H102-Final org.jboss.tools.vpe.feature.feature.group JBoss by Red Hat
JBoss WebServices Tools 1.2.2.v20120611-1829-H137-Final org.jboss.tools.ws.feature.feature.group JBoss by Red Hat
JBossAS Tools 2.3.0.v20120615-1559-H138-Final org.jboss.ide.eclipse.as.feature.feature.group JBoss by Red Hat
JMX Console 1.2.0.v20120611-1733-H71-Final org.jboss.tools.jmx.feature.feature.group JBoss by Red Hat
m2e - slf4j over logback logging (Optional) 1.0.200.20111228-1245 org.eclipse.m2e.logback.feature.feature.group Eclipse.org - m2e
m2e connector for build-helper-maven-plugin 0.14.0.201109282148 org.sonatype.m2e.buildhelper.feature.feature.group Sonatype, Inc.
m2e connector for jaxb2 2.0.0.201203261829 org.bitstrings.eclipse.m2e.connectors.jaxb2.features.feature.group bitstrings.org
m2e connector for maven-scm-plugin 1.0.0.201107091852 org.objectledge.maven.connectors.scm.feature.group ObjectLedge.org
m2e Connector for XML Transform 0.4.0 nl.mwensveen.m2e.extras.xml.transform.feature.feature.group MWensveen.nl
Maven Integration for Eclipse JDT APT 1.0.0.201206052025 org.jboss.tools.maven.apt.feature.feature.group JBoss, by Red Hat
Maven SCM Handler for Subversive 0.13.0.201106211115 org.sonatype.m2e.subversive.feature.feature.group Sonatype, Inc.
Native JavaHL 1.6 Implementation (Optional) 2.3.0.I20120413-1700 org.polarion.eclipse.team.svn.connector.javahl16.feature.group Polarion Software
Native JavaHL 1.7 Implementation (Optional) 2.3.0.I20120520-1700 org.polarion.eclipse.team.svn.connector.javahl17.feature.group Polarion Software
OSGi Application Development Tools 1.5.0.v20120530_1235 com.ibm.osgi.wdt.feature.feature.group IBM
Project Examples 1.2.1.v20120612-0012-H106-Final org.jboss.tools.project.examples.feature.feature.group JBoss by Red Hat
Seam 3 Tools 1.2.0.v20120611-1827-H85-Final org.jboss.tools.cdi.seam.feature.feature.group JBoss by Red Hat
Seam Tools 3.3.0.v20120612-1916-H130-Final org.jboss.tools.seam.feature.feature.group JBoss by Red Hat
Spring IDE AOP Extension (optional) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.aop.feature.feature.group Spring IDE Developers
Spring IDE Autowire Extension (optional) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.autowire.feature.feature.group featureProvider
Spring IDE Batch Extension (optional) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.batch.feature.feature.group featureProvider
Spring IDE Core (required) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.feature.feature.group Spring IDE Developers
Spring IDE Integration, Flex and Web Services Extension (optional) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.integration.feature.feature.group featureProvider
Spring IDE OSGi Extension (optional) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.osgi.feature.feature.group Spring IDE Developers
Spring IDE Security Extension (optional) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.security.feature.feature.group featureProvider
Spring IDE Web Flow Extension (optional) 2.9.2.201205070117-RELEASE org.springframework.ide.eclipse.webflow.feature.feature.group Spring IDE Developers
Subversive SVN Connectors 2.3.0.I20120520-1700 org.polarion.eclipse.team.svn.connector.feature.group Polarion Software
Subversive SVN Integration for the Mylyn Project (Optional) (Incubation) 0.7.9.I20110602-1700 org.eclipse.team.svn.mylyn.feature.group Eclipse.org
Subversive SVN JDT Ignore Extensions (Optional) (Incubation) 0.7.9.I20111119-1700 org.eclipse.team.svn.resource.ignore.rules.jdt.feature.group Eclipse.org
Subversive SVN Team Provider (Incubation) 0.7.9.I20120520-1700 org.eclipse.team.svn.feature.group Eclipse.org
Subversive SVN Team Provider Localization (Optional) (Incubation) 0.7.9.I20120316-1700 org.eclipse.team.svn.nl1.feature.group Eclipse.org
Subversive SVN Team Provider Sources (Incubation) 0.7.9.I20120520-1700 org.eclipse.team.svn.source.feature.group Eclipse.org
SVNKit 1.3.7 Implementation (Optional) 2.3.0.I20120413-1700 org.polarion.eclipse.team.svn.connector.svnkit16.feature.group Polarion Software
SVNKit 1.7.4 Implementation (Optional) 2.3.0.I20120520-1700 org.polarion.eclipse.team.svn.connector.svnkit17.feature.group Polarion Software
Web Development Tools 1.0.0.v20120530_1235 com.ibm.wdt.webtools.top.feature.feature.group IBM
WebSphere® Application Server V8.0 Tools 1.0.100.v20120530_1235 com.ibm.websphere.wdt.st.v8.feature.group IBM