p:fileUpload NullPointerException

2019-08-01 05:04发布

站内文章 / 前沿技术
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问题:

I am pretty new at developing in JSF and I am busy building a project that requires file uploads but every time I run the uploader I get a java.lang.NullPointerException could anyone please help me with this problem, I have searched the internet extensively and cannot find a solution that works.

I am using NetBeans 7.1.1 and GlassFish to deploy.

My code is as follows:

I have added the following jars to my library: primefaces-3.2.jar commons-io-2.3.jar commons-fileupload-1.2.2.jar

This is my XHTML

<!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:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui">
<h:head>
  <link href="${request.contextPath}/styles.css" type="text/css" rel="stylesheet"/>
  <title>Tutor Management System</title>

</h:head>
<h:body>

         <h:form enctype="multipart/form-data">  

    <p:messages showDetail="true"/>  

    <p:fileUpload value="#{myBean.file}" mode="simple" />  

    <p:commandButton value="Submit" ajax="false"  
                actionListener="#{myBean.upload}"/>  

</h:form>  

</h:body>
</html>

This is my Backing Bean

package BackingBean;

/**
 *
 * @author chrissalerno24
 */
import java.io.*;
import java.util.Map;
import javax.enterprise.context.SessionScoped;
import javax.faces.application.FacesMessage;
import javax.faces.bean.ManagedBean;
import javax.faces.context.ExternalContext;
import javax.faces.context.FacesContext;
import org.primefaces.model.UploadedFile;

@ManagedBean(name="myBean")
public class MyBean implements java.io.Serializable {  

    private UploadedFile file; 
    private static final String MBN = "usernameApplication";
    ExternalContext externalContext = FacesContext.getCurrentInstance().getExternalContext();
    Map<String, Object> sessionMap = externalContext.getSessionMap();


    public UploadedFile getFile() {  
        return file;  
    }  

    public void setFile(UploadedFile file) {  
        this.file = file;  
    }  

    public void upload() {  
        FacesMessage msg = new FacesMessage("Succesful", file.getFileName() + " is uploaded.");  
        FacesContext.getCurrentInstance().addMessage(null, msg);  
    }
}

This is my web.xml file

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
     version="3.0">

    <filter>
        <filter-name>PrimeFaces FileUpload Filter</filter-name>
        <filter-class>org.primefaces.webapp.filter.FileUploadFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>PrimeFaces FileUpload Filter</filter-name>
        <servlet-name>Faces Servlet</servlet-name>
    </filter-mapping>

    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>



    <error-page>
        <error-code>404</error-code>
        <location>/404.jsf</location>
    </error-page>

    <context-param>  
    <param-name>primefaces.THEME</param-name>  
    <param-value>aristo</param-value>  
</context-param>  

</web-app>

I am using PrimeFaces 3.2, JSF 2.0 and GlassFish 3.1.1

Any help would be greatly appreciated.

Here is the stack trace:

SEVERE: Received 'java.lang.NullPointerException' when invoking action listener '#{myBean.upload}' for component 'j_idt9'
SEVERE: java.lang.NullPointerException
    at BackingBean.MyBean.upload(MyBean.java:38)
    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 com.sun.el.parser.AstValue.invoke(AstValue.java:254)
    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:302)
    at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:39)
    at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:153)
    at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769)
    at javax.faces.component.UICommand.broadcast(UICommand.java:300)
    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:1542)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
    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$AdapterCallable.call(ContainerMapper.java:317)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:849)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:746)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1045)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:228)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:680)

SEVERE: JSF1073: javax.faces.event.AbortProcessingException caught during processing of INVOKE_APPLICATION 5 : UIComponent-ClientId=j_idt6:j_idt9, Message=java.lang.NullPointerException
SEVERE: java.lang.NullPointerException
javax.faces.event.AbortProcessingException: java.lang.NullPointerException
    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:182)
    at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769)
    at javax.faces.component.UICommand.broadcast(UICommand.java:300)
    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:1542)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
    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$AdapterCallable.call(ContainerMapper.java:317)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:849)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:746)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1045)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:228)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:680)
Caused by: java.lang.NullPointerException
    at BackingBean.MyBean.upload(MyBean.java:38)
    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 com.sun.el.parser.AstValue.invoke(AstValue.java:254)
    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:302)
    at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:39)
    at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:153)
    ... 33 more

The exact line where the uploadFile is breaking is as follows:

FacesMessage msg = new FacesMessage("Succesful", file.getFileName() + " is uploaded.");

This is my faces-config.xml file:

<?xml version='1.0' encoding='UTF-8'?>

<!-- =========== FULL CONFIGURATION FILE ================================== -->

<faces-config version="2.0"
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd">
    <managed-bean>
        <managed-bean-name>StudentBean</managed-bean-name>
        <managed-bean-class>BackingBean.TutorBackingBean</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>LoginBean</managed-bean-name>
        <managed-bean-class>BackingBean.LoginBackingBean</managed-bean-class>
        <managed-bean-scope>request</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>LecturerBean</managed-bean-name>
        <managed-bean-class>BackingBean.LecturerBackingBean</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>ApplicationBean</managed-bean-name>
        <managed-bean-class>BackingBean.ApplicationBackingBean</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>myBean</managed-bean-name>
        <managed-bean-class>BackingBean.MyBean</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>AdminBean</managed-bean-name>
        <managed-bean-class>BackingBean.AdminBackingBean</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>

</faces-config>

chrissalerno24

回答1:

Your managed bean does not have any scope. This way JSF defaults to @NoneScoped. So a new one is created on every single #{myBean} evaluation in EL. Right now there are effectively two created when you select a file and submit the button. The file is set on the first one and the action method is invoked on the second one (which doesn't have the file at all).

You need to put it in a bit wider scope, e.g. the request scope.

import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;

@ManagedBean
@RequestScoped
public class MyBean {
    // ...
}

By the way, you've there a dangling import javax.enterprise.context.SessionScoped;. This is specific to CDI and would work only when you're managing beans by CDI @Named instead of by JSF @ManagedBean. Make sure that you use the right package for the bean scope. There's namely also a javax.faces.bean.SessionScoped for the case you need a session scoped JSF managed bean.



标签： jsf file-upload glassfish primefaces nullpointerexception
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