1

我是 JSF 开发的新手，我正忙于构建一个需要上传文件的项目，但是每次运行上传器时，我都会收到 java.lang.NullPointerException 任何人都可以帮我解决这个问题，我已经广泛搜索了互联网并且找不到有效的解决方案。

我正在使用 NetBeans 7.1.1 和 GlassFish 进行部署。

我的代码如下：

我已将以下 jar 添加到我的库中：primefaces-3.2.jar commons-io-2.3.jar commons-fileupload-1.2.2.jar

这是我的 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>

这是我的支持豆

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);  
    }
}

这是我的 web.xml 文件

<?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>

我正在使用 PrimeFaces 3.2、JSF 2.0 和 GlassFish 3.1.1

任何帮助将不胜感激。

这是堆栈跟踪：

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

uploadFile 中断的确切行如下：

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

这是我的 faces-config.xml 文件：

<?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>

克里斯萨勒诺24

4

1 回答 1

4

您的托管 bean 没有任何作用域。这种方式 JSF 默认为@NoneScoped. #{myBean}因此，EL 中的每一次评估都会创建一个新的评估。现在，当您选择一个文件并提交按钮时，实际上创建了两个。该文件设置在第一个上，并且在第二个上调用操作方法（根本没有文件）。

您需要将其放在更广泛的范围内，例如请求范围。

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

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

顺便说一句，你有一个悬垂的import javax.enterprise.context.SessionScoped;. 这是特定于 CDI 的，并且仅当您通过 CDI@Named而不是 JSF管理 bean 时才有效@ManagedBean。确保为 bean 范围使用正确的包。也就是javax.faces.bean.SessionScoped你需要一个会话范围的 JSF 托管 bean 的情况。

于 2012-05-19T10:54:38.983 回答