我正在尝试在数据库中插入图片的详细信息。每当我提交数据时，我在PictureBean的第52行得到一个空点异常，它表明uploadedFile.getSize（）返回null。图片的其他细节不会造成任何问题。
这是我的xhtml文件
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:p="http://primefaces.org/ui">
<h:head>Add Photo</h:head>
<h:form enctype="multipart/form-data">
<h:panelGrid columns="2">
<h:outputText value="Photo"/>
<p:fileUpload fileUploadListener="#{pictureBean.handleFileUpload}"/>
<h:outputText value="Picture ID: " />
<p:inputText styleClass="outputLabel"
value="#{pictureBean.picture.pictureId}" />
<h:outputText value="Picture Name: " />
<p:inputText styleClass="outputLabel"
value="#{pictureBean.picture.pictureName}" />
<h:outputText value="Picture Details: " />
<p:inputText styleClass="outputLabel"
value="#{pictureBean.picture.pictureDetails}" />
<h:outputText value="Album ID: " />
<p:inputText styleClass="outlabel" value="#{pictureBean.picture.albumId}"/>
<p:commandButton value="Add Photo" action="#{pictureBean.save}"/>
</h:panelGrid>
</h:form>
</html>
这是我的PictureBean
package com.bean;
import javax.faces.context.FacesContext;
import javax.faces.event.PhaseId;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.servlet.http.HttpSession;
import org.primefaces.event.FileUploadEvent;
import org.primefaces.model.UploadedFile;
import com.entity.Picture;
import com.entity.User;
public class PictureBean {
Picture picture;
private UploadedFile uploadedFile;
private EntityManager em;
public PictureBean(){
picture = new Picture();
EntityManagerFactory emf=Persistence.createEntityManagerFactory("FreeBird");
em =emf.createEntityManager();
}
public Picture getPicture() {
return picture;
}
public void setPicture(Picture picture) {
this.picture = picture;
}
public void handleFileUpload(FileUploadEvent e) {
System.out.println("file handler called");
uploadedFile = e.getFile();
String fileName=uploadedFile.getFileName();
fileName=fileName.substring(fileName.lastIndexOf("\\")+1);
System.out.println(fileName);
byte[] a = uploadedFile.getContents();
PhaseId currentPhaseId = FacesContext.getCurrentInstance().getCurrentPhaseId();
System.out.println("current phase id"+currentPhaseId);
picture.setPicture(a);
}
public String save(){
FacesContext context = FacesContext.getCurrentInstance();
HttpSession session = (HttpSession) context.getExternalContext().getSession(true);
User user = (User) session.getAttribute("userdet");
picture.setEmail(user.getEmail());
picture.setPictureSize(uploadedFile.getSize());
System.out.println("picture save called");
em.getTransaction().begin();
em.persist(picture);
em.getTransaction().commit();
return "success";
}
}
以下是我的例外情况。
WARNING: #{pictureBean.save}: java.lang.NullPointerException
javax.faces.FacesException: #{pictureBean.save}: java.lang.NullPointerException
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:79)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:722)
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)
... 36 more
Caused by: java.lang.NullPointerException
at com.bean.PictureBean.save(PictureBean.java:52)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.sun.el.parser.AstValue.invoke(AstValue.java:254)
at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:302)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
... 37 more
答案 0 :(得分：1)
表明uploadedFile.getSize（）返回null。
不，它没有返回null，这不可能导致这个特定的堆栈跟踪。 uploadedFile本身就是null。因此，它没有指向任何，因此任何使用句点.运算符访问/调用它的尝试都会产生NullPointerException，与its javadoc提示完全相同我们。
在这个特定的情况下，如果bean是请求作用域并且文件实际上是在不同的HTTP请求中上传的话，就会发生这种情况。您在上一个问题中已经提供了两种可能的解决方案：Image not getting updated：
<p:fileUpload>设为mode="simple"。第三种解决方案是预先执行nullcheck。由于您没有将其设置为required="true"，另一个可能的原因是最终用户根本没有选择/发送任何文件。
if (uploadedFile != null) {
picture.setPictureSize(uploadedFile.getSize());
}