我遇到了一个非常奇怪的问题。我的应用程序运行得相当好，我正在优化它（我从其他开发人员那里继承了它）。
该项目使用Hibernate 4和MS SQL Server，并使用Primefaces在Tomcat 8上运行。我最近回到Primefaces的LazyDateModel，开始使用懒惰加载（以前的开发人员将所有懒惰加载设置为false），在恢复工作状态时遇到了一些问题。其中大多数我都可以自己解决，但这一次让我不知所措。
<query name="assayByLineAndDateRange">
<![CDATA[from Assay a where a.line.number = :line and a.time >= :startDate
and a.time < :endDate order by a.time DESC]]>
</query>
上面的HQL查询将导致com.microsoft.sqlserver.jdbc.Nanos的最终ClassNotFoundException，我已经验证了它存在于我的项目类路径中。
现在，对于奇怪的部分：当我删除查询的and条件时，应用程序运行良好，如下所示：
<query name="assayByLineAndDateRange">
<![CDATA[from Assay a where a.line.number = :line order by a.time DESC]]>
</query>
当我在util类中调用query.iterate（）时，会出现确切的问题，但我不明白为什么。以下是有问题的代码片段：
protected List<T> getList(Query query) {
List<T> list = new ArrayList<T>();
System.out.println("Query name: " + query.getQueryString());
try {
@SuppressWarnings("rawtypes")
Iterator i = query.iterate();
System.out.println("This line does not print");
while(i.hasNext()) {
list.add(getNext(i));
}
return list;
} catch(Exception e) {
System.out.println("CAUSE: " + e.getCause().toString());
e.printStackTrace();
return null;
}
请注意，这段代码对其他所有查询都非常适用，包括使用and运算符的查询。
以下是来自Assay的映射文件的相关部分：
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.app.gen.model.data.Assay" table="ASSAY" schema="GEN">
<id name="id" type="java.lang.Long" unsaved-value="0">
<column name="ID" precision="10" scale="0"/>
<generator class="identity"/>
</id>
<property name="time" type="timestamp">
<column name="TIME" not-null="true" unique="true"/>
</property>
<many-to-one name="line" class="com.app.gen.model.data.Line" cascade="none">
<column name="LINE_ID" not-null="true"/>
</many-to-one>
</class>
</hibernate-mapping>
此外，我还测试了这些参数，以确保它们被正确地传递。最重要的是，在我实现延迟加载之前，这个查询运行良好。以下是用于延迟加载到Primefaces DataTable:的过载load方法
@Override
public List<Assay> load(int first, int pageSize, String sortField, SortOrder sortOrder, Map<String,String> filters) {
try {
if(null==lineAssays)
lineAssays = new HashMap<Integer,List<Assay>>();
if(null == lineAssays.get(getLineNumber())) {
if(log.isDebugEnabled()) { log.debug("Fetching Line Assays..."); }
List<Assay> assays = GenServiceFactory.create().fetchAssaysByLineAndDateRange(getLineNumber(), getStartDate(), getEndDate());
lineAssays.put(getLineNumber(),assays);
}
} catch(Exception e) {
System.out.println("AN ERROR OCCURED!");
e.printStackTrace();
}
try {
int numAssays = lineAssays.get(getLineNumber()).size();
this.setRowCount(numAssays);
if(numAssays > pageSize) {
try {
return lineAssays.get(line).subList(first, first + pageSize);
}
catch(IndexOutOfBoundsException e) {
return lineAssays.get(line).subList(first, first + (numAssays % pageSize));
}
}
else {
return lineAssays.get(line);
}
} catch(NullPointerException e1) {
System.out.println("lineAssays is null");
}
return null;
}
以下是异常的堆栈跟踪：
DEBUG (2015-02-03 14:57:50) [http-apr-8080-exec-34] (LazyAssayLoader.java:72) - Fetching Line Assays...
Query name:
from Assay a where a.line.number = :line and a.time >= :startDate and a.time < :endDate order by a.time DESC
CAUSE: java.lang.ClassNotFoundException
java.lang.IllegalStateException: Can't overwrite cause with java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load com.microsoft.sqlserver.jdbc.Nanos. The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
at java.lang.Throwable.initCause(Throwable.java:457)
at org.apache.catalina.loader.WebappClassLoader.checkStateForClassLoading(WebappClassLoader.java:1331)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1212)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1173)
at com.microsoft.sqlserver.jdbc.TDSWriter.writeScaledTemporal(IOBuffer.java:4278)
at com.microsoft.sqlserver.jdbc.TDSWriter.writeRPCDateTime2(IOBuffer.java:4184)
at com.microsoft.sqlserver.jdbc.DTV$SendByRPCOp.sendTemporal(dtv.java:584)
at com.microsoft.sqlserver.jdbc.DTV$SendByRPCOp.execute(dtv.java:356)
at com.microsoft.sqlserver.jdbc.DTV.executeOp(dtv.java:1025)
at com.microsoft.sqlserver.jdbc.DTV.sendByRPC(dtv.java:1116)
at com.microsoft.sqlserver.jdbc.Parameter.sendByRPC(Parameter.java:660)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.sendParamsByRPC(SQLServerPreparedStatement.java:473)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doPrepExec(SQLServerPreparedStatement.java:628)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doExecutePreparedStatement(SQLServerPreparedStatement.java:400)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement$PrepStmtExecCmd.doExecute(SQLServerPreparedStatement.java:350)
at com.microsoft.sqlserver.jdbc.TDSCommand.execute(IOBuffer.java:5696)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(SQLServerConnection.java:1716)
at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeCommand(SQLServerStatement.java:180)
at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeStatement(SQLServerStatement.java:155)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.executeQuery(SQLServerPreparedStatement.java:285)
at org.apache.tomcat.dbcp.dbcp2.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:82)
at org.apache.tomcat.dbcp.dbcp2.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:82)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:56)
at org.hibernate.loader.Loader.getResultSet(Loader.java:2040)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1837)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1816)
at org.hibernate.loader.hql.QueryLoader.iterate(QueryLoader.java:518)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.iterate(QueryTranslatorImpl.java:399)
at org.hibernate.engine.query.spi.HQLQueryPlan.performIterate(HQLQueryPlan.java:245)
at org.hibernate.internal.SessionImpl.iterate(SessionImpl.java:1331)
at org.hibernate.internal.QueryImpl.iterate(QueryImpl.java:68)
at com.core.service.HibernateService$AbstractHQLQuery.getList(HibernateService.java:120)
at com.core.service.HibernateService$AbstractHQLQuery.getList(HibernateService.java:138)
at com.urenco.iphex.service.IphexService.fetchAssaysByLineAndDateRange(IphexService.java:77)
at com.urenco.iphex.view.lazy.LazyAssayLoader.load(LazyAssayLoader.java:73)
at org.primefaces.component.datatable.DataTable.loadLazyData(DataTable.java:731)
at org.primefaces.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:79)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:63)
at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:47)
at org.primefaces.component.panel.PanelRenderer.encodeContent(PanelRenderer.java:202)
at org.primefaces.component.panel.PanelRenderer.encodeMarkup(PanelRenderer.java:119)
at org.primefaces.component.panel.PanelRenderer.encodeEnd(PanelRenderer.java:56)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1786)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1782)
at org.primefaces.component.tabview.TabViewRenderer.encodeTabContent(TabViewRenderer.java:274)
at org.primefaces.component.tabview.TabViewRenderer.encodeContents(TabViewRenderer.java:253)
at org.primefaces.component.tabview.TabViewRenderer.encodeMarkup(TabViewRenderer.java:127)
at org.primefaces.component.tabview.TabViewRenderer.encodeEnd(TabViewRenderer.java:71)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:312)
at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:105)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1779)
at com.sun.faces.renderkit.html_basic.CompositeRenderer.encodeChildren(CompositeRenderer.java:78)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:304)
at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:105)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1779)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1779)
at com.sun.faces.context.PartialViewContextImpl$PhaseAwareVisitCallback.visit(PartialViewContextImpl.java:518)
at com.sun.faces.component.visit.PartialVisitContext.invokeVisitCallback(PartialVisitContext.java:183)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1612)
at javax.faces.component.UIForm.visitTree(UIForm.java:371)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1623)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1623)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1623)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1623)
at com.sun.faces.context.PartialViewContextImpl.processComponents(PartialViewContextImpl.java:376)
at com.sun.faces.context.PartialViewContextImpl.processPartial(PartialViewContextImpl.java:297)
at javax.faces.context.PartialViewContextWrapper.processPartial(PartialViewContextWrapper.java:183)
at javax.faces.component.UIViewRoot.encodeChildren(UIViewRoot.java:981)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1779)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:409)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:125)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:616)
lineAssays is null
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:534)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:277)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2381)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2370)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException
at org.apache.catalina.loader.WebappClassLoader.checkStateForClassLoading(WebappClassLoader.java:1330)
... 103 more
很抱歉出现了文字墙，但非常感谢您的帮助！
我认为ClassNotFoundException不是真正的问题。如果你看看这里（第1328行）的源代码
org.apache.catalina.loader.WebappClassLoader.checkStateForClassLoading
它在实际尝试加载类时并没有失败，在加载类之前验证web应用程序的当前状态时也会失败，所以这个异常有点误导。
真正的问题似乎是你的应用程序在加载数据时处于无效状态。查找有关该问题的更多信息指的是Tomcat缓存旧版本应用程序代码的问题。不确定是否是这种情况，或者您是否尝试过从干净状态重新启动服务器。至少你可以肯定，类加载并不是这里真正的问题。