我已经阅读了很多关于这个错误的信息，原因是：
但在我的情况下，这个类是jdk类，我搜索没有在我的应用程序下找到这个类。
任何线索都会非常有用。
异常堆栈：
2012-10-31 14:09:58,319 WARN [org.jboss.detailed.classloader.ClassLoaderManager] (http-0.0.0.0-8080-1:) Unexpected error during load of:javax.sql.DataSource
java.lang.LinkageError: loader constraint violation: loader (instance of org/jboss/classloader/spi/base/BaseClassLoader) previously initiated loading for a different type with name "javax/sql/DataSource"
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:67)
at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:633)
at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:592)
at java.security.AccessController.doPrivileged(Native Method)
at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:591)
at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:568)
at org.jboss.classloader.spi.base.BaseDelegateLoader.loadClass(BaseDelegateLoader.java:135)
at org.jboss.classloader.spi.filter.FilteredDelegateLoader.loadClass(FilteredDelegateLoader.java:131)
at org.jboss.classloader.spi.base.ClassLoadingTask$ThreadTask.run(ClassLoadingTask.java:455)
at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:267)
at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:166)
at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:287)
at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:1163)
at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:862)
at org.jboss.classloader.spi.base.BaseClassLoader.doLoadClass(BaseClassLoader.java:502)
at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:447)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at com.lombardrisk.webgui.dwr.ajax_search.UmbrellaNettingFundsSearch.getBranchesByAgreementId(UmbrellaNettingFundsSearch.java:199)
at com.lombardrisk.webgui.dwr.ajax_search.UmbrellaNettingFundsSearch.buildConditionOfPrinAndCpty(UmbrellaNettingFundsSearch.java:177)
at com.lombardrisk.webgui.dwr.ajax_search.UmbrellaNettingFundsSearch.getFunds(UmbrellaNettingFundsSearch.java:58)
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.directwebremoting.impl.ExecuteAjaxFilter.doFilter(ExecuteAjaxFilter.java:34)
at org.directwebremoting.impl.DefaultRemoter$1.doFilter(DefaultRemoter.java:428)
at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:431)
at org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:283)
at org.directwebremoting.servlet.PlainCallHandler.handle(PlainCallHandler.java:52)
at org.directwebremoting.servlet.UrlProcessor.handle(UrlProcessor.java:101)
at org.directwebremoting.servlet.DwrServlet.doPost(DwrServlet.java:146)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.lombardrisk.webgui.filter.ValidRequestFilter.doFilter(ValidRequestFilter.java:41)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:183)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:525)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:95)
at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)
at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.jboss.web.tomcat.service.request.ActiveRequestResponseCacheValve.internalProcess(ActiveRequestResponseCacheValve.java:74)
at org.jboss.web.tomcat.service.request.ActiveRequestResponseCacheValve.invoke(ActiveRequestResponseCacheValve.java:47)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:829)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:599)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:451)
at java.lang.Thread.run(Thread.java:662)
答案 0 :(得分：0)
此问题已解决
还有另一个包含此类的jar（jdbc2_0-stdext.jar），并由我们带到app。
B类是正常的，因为在另一个X.jar中调用了con = ds.getConnection，而在它自己的Y.war中调用了A类，而这个jdbc2_0-stdext.jar是Y.war中的包