我在JSF 1.2 / Rich Faces 3.3 / Tomcat 6 / Java 1.6中开发了应用程序。在页面中，我有一个用于输入长值的文本框。如果我将文本框留空并在bean中检查其值如下： -
if(this.employeeAge.toString() == "" || this.employeeAge == null ||
this.employeeAge == 0) // this is code line no 809 generating error
{ System.out.println("employee age not entered");
}
片段如下： -
<h:outputText value="Employee Age" />
<h:inputText value="#{employeeBean.employeeAge}" id="empAge" maxlength="3" />
这适用于apache tomcat，但在Web Sphere上，我收到以下错误
[12/16/14 12:22:10:641 PKT] 00000037 webapp E com.ibm.ws.webcontainer.webapp.WebApp logServletError SRVE0293E: [Servlet Error]-[Faces Servlet]: javax
.faces.FacesException: #{employeeBean.save}: java.lang.NullPointerException
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
at javax.faces.component.UICommand.broadcast(UICommand.java:387)
at org.ajax4jsf.component.AjaxActionComponent.broadcast(AjaxActionComponent.java:55)
at org.ajax4jsf.component.AjaxViewRoot.processEvents(AjaxViewRoot.java:324)
at org.ajax4jsf.component.AjaxViewRoot.broadcastEvents(AjaxViewRoot.java:299)
at org.ajax4jsf.component.AjaxViewRoot.processPhase(AjaxViewRoot.java:256)
at org.ajax4jsf.component.AjaxViewRoot.processApplication(AjaxViewRoot.java:469)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:265)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1657)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1597)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:131)
at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178)
at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290)
at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:388)
at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515)
at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:188)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:116)
at restricted.AuthorizationFilter.doFilter(AuthorizationFilter.java:162)
at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:188)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:116)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain._doFilter(WebAppFilterChain.java:77)
at com.ibm.ws.webcontainer.filter.WebAppFilterManager.doFilter(WebAppFilterManager.java:908)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:934)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:502)
at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:179)
at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3826)
at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:276)
at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:931)
at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1583)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:186)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:445)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:504)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:301)
at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:83)
at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1563)
Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
... 44 more
Caused by: java.lang.NullPointerException
at mtech.beans.EmployeeBean.save(EmployeeBean.java:809)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:48)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:600)
at org.apache.el.parser.AstValue.invoke(AstValue.java:159)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
at org.apache.jasper.el.JspMethodExpression.invoke(JspMethodExpression.java:67)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
... 45 more
要避免此错误，需要做些什么。
答案 0 :(得分：2)
if(this.employeeAge.toString() == "" || this.employeeAge == null ||
this.employeeAge == 0) // this is code line no 809 generating erro
您首先使用employeeAge值（适用于toString()）， 后检查它是否为null。
在if中，表达式按顺序进行评估。此外，它们是短路的（如果您有||且左侧表达式为true，则不会评估正确的表达式，因为true || anything -> true。
只需更改订单
if (this.employeeAge == null || this.employeeAge.toString() == "" ||
this.employeeAge == 0) // this is code line no 809 generating erro
如果employeeAge为空，则第一个表达式将返回true，而其他任何表达式都不会被评估。