我有一個JSF頁面的託管bean，它在構造函數中執行JPA調用來填充bean中的字段。我在繼續調用一個實體（填充數據以進行測試）方面遇到了一些麻煩。我期待它拋出某種異常，因爲它不起作用，但我沒有得到任何東西。只是它的赫克我試過如下：JSF隱藏異常？
Query newQuery = em.createQuery("Bad Syntax");
List newList = newQuery.getResultList();
我期望的IllegalArgumentException在這裏，因爲查詢字符串是完全無效，但頁面仍然加載，我看不出有任何異常的任何地方。
我是否期待這種例外？如果是這樣，爲什麼我沒有看到它？
那麼，NetBeans似乎存在某種問題，無法正確重新部署所有內容。當我開始排除故障時，我一直在運行乾淨的版本，但在讓事情坐了幾天回去之後，我現在看到了我期望看到的內容。
所致：java.lang.IllegalArgumentException異常： 異常描述：：語法錯誤解析查詢[壞語法]，第1行，第0列：意外的標記[同時創造在EntityManager的查詢時發生異常壞]。
我不知道什麼教訓，我真的從中學到，但它肯定刪除了一些我信任的NetBeans。
默認情況下，它不會抑制異常。作爲一個快速測試，我試過如下：
package com.example;
import javax.faces.bean.ManagedBean;
@ManagedBean
public class Bean {
public Bean() {
throw new IllegalArgumentException("No!");
}
}
與
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html">
<h:head>
<title>test</title>
</h:head>
<h:body>
#{bean}
</h:body>
</html>
和我同在網頁瀏覽器下面的跟蹤一個不錯的默認錯誤頁：
javax.el.ELException: /test.xhtml: Cant instantiate class: com.example.Bean.
at com.sun.faces.facelets.compiler.TextInstruction.write(TextInstruction.java:83)
at com.sun.faces.facelets.compiler.UIInstructions.encodeBegin(UIInstructions.java:75)
at com.sun.faces.facelets.compiler.UILeaf.encodeAll(UILeaf.java:176)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127)
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:313)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)
Caused by: com.sun.faces.mgbean.ManagedBeanCreationException: Cant instantiate class: com.example.Bean.
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:193)
at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:102)
at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:405)
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:267)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:86)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:54)
at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:61)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
at com.sun.faces.facelets.el.ELText$ELTextVariable.writeText(ELText.java:217)
at com.sun.faces.facelets.el.ELText$ELTextComposite.writeText(ELText.java:141)
at com.sun.faces.facelets.compiler.TextInstruction.write(TextInstruction.java:78)
... 25 more
Caused by: java.lang.IllegalArgumentException: No!
at com.example.Bean.<init>(Bean.java:9)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:188)
... 36 more
1-jun-2010 13:51:06 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet Faces Servlet threw exception
java.lang.IllegalArgumentException: No!
at com.example.Bean.<init>(Bean.java:9)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:188)
at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:102)
at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:405)
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:267)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:86)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:54)
at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:61)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
at com.sun.faces.facelets.el.ELText$ELTextVariable.writeText(ELText.java:217)
at com.sun.faces.facelets.el.ELText$ELTextComposite.writeText(ELText.java:141)
at com.sun.faces.facelets.compiler.TextInstruction.write(TextInstruction.java:78)
at com.sun.faces.facelets.compiler.UIInstructions.encodeBegin(UIInstructions.java:75)
at com.sun.faces.facelets.compiler.UILeaf.encodeAll(UILeaf.java:176)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127)
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:313)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)
所以你的問題可能在別的地方。你運行了一個調試器嗎？
我已經運行了一個調試器，但我不確定要查找什麼，所以目前我沒有任何有用的信息。我注意到的一件事是，它似乎沒有停止在創建查詢的行上。 – bshacklett 2010-06-01 19:08:56
然後你沒有運行你認爲你正在運行的代碼。 – BalusC 2010-06-01 19:18:15
如果一條線在它周圍沒有分支時可以跳過這條線嗎？我想，我必須發佈這個bean的內容。今晚我會盡力做到這一點。 – bshacklett 2010-06-02 16:45:45
您是否嘗試過在查詢執行後查看「newList」的值是什麼？ – pakore 2010-06-01 09:32:42