我尝试使用JSF 2.1和Primefaces 3.5进行简单的文件上传，我可以在UI中附加文件。附加文件后单击Submit按钮，它将返回空指针异常。
upload2.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>
<title>Journaldev Tutorial</title>
</h:head>
<h:body>
<h:form enctype="multipart/form-data">
<p:fileUpload value="#{fileUploadManagedBean.file}" mode="simple"></p:fileUpload>
<p:separator/>
<h:commandButton value="Upload" ajax="false" action="#{fileUploadManagedBean.dummyAction}"></h:commandButton>
</h:form>
</h:body>
</html>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>Testty3</display-name>
<welcome-file-list>
<welcome-file>faces/upload2.xhtml</welcome-file>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
<multipart-config/>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>/faces/*</url-pattern>
<url-pattern>*.jsf</url-pattern>
<url-pattern>/icefaces/*</url-pattern>
</servlet-mapping>
<!-- <filter>
<filter-name>MyFacesExtensionsFilter</filter-name>
<filter-class>org.apache.myfaces.webapp.filter.ExtensionsFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>MyFacesExtensionsFilter</filter-name>
<servlet-name>Faces Servlet</servlet-name>
</filter-mapping> -->
<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>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
</filter-mapping>
<!-- <context-param>
<description>State saving method: 'client' or 'server' (=default). See JSF Specification 2.5.2</description>
<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>client</param-value>
</context-param> -->
<context-param>
<param-name>primefaces.UPLOADER</param-name>
<param-value>commons</param-value>
</context-param>
<!-- <listener>
<listener-class>com.sun.faces.config.ConfigureListener</listener-class>
</listener> -->
<context-param>
<param-name>javax.servlet.jsp.jstl.fmt.localizationContext</param-name>
<param-value>resources.application</param-value>
</context-param>
<context-param>
<description>State saving method: 'client' or 'server' (=default). See JSF Specification 2.5.2</description>
<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>server</param-value>
</context-param>
<context-param>
<description>
This parameter tells MyFaces if javascript code should be allowed in
the rendered HTML output.
If javascript is allowed, command_link anchors will have javascript code
that submits the corresponding form.
If javascript is not allowed, the state saving info and nested parameters
will be added as url parameters.
Default is 'true'</description>
<param-name>org.apache.myfaces.ALLOW_JAVASCRIPT</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<description>
If true, rendered HTML code will be formatted, so that it is 'human-readable'
i.e. additional line separators and whitespace will be written, that do not
influence the HTML code.
Default is 'true'</description>
<param-name>org.apache.myfaces.PRETTY_HTML</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>org.apache.myfaces.DETECT_JAVASCRIPT</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<description>
If true, a javascript function will be rendered that is able to restore the
former vertical scroll on every request. Convenient feature if you have pages
with long lists and you do not want the browser page to always jump to the top
if you trigger a link or button action that stays on the same page.
Default is 'false'
</description>
<param-name>org.apache.myfaces.AUTO_SCROLL</param-name>
<param-value>true</param-value>
</context-param>
<listener>
<listener-class>org.apache.myfaces.webapp.StartupServletContextListener</listener-class>
</listener>
<context-param>
<param-name>javax.faces.PROJECT_STAGE</param-name>
<param-value>Development</param-value>
</context-param>
<context-param>
<param-name>javax.faces.FACELETS_SKIP_COMMENTS</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>org.icefaces.coalesceResources</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>org.icefaces.strictSessionTimeout</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>org.apache.myfaces.REFRESH_TRANSIENT_BUILD_ON_PSS</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>org.apache.myfaces.REFRESH_TRANSIENT_BUILD_ON_PSS_PRESERVE_STATE</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>org.apache.myfaces.SERIALIZE_STATE_IN_SESSION</param-name>
<param-value>false</param-value>
</context-param>
<mime-mapping>
<extension>png</extension>
<mime-type>image/png</mime-type>
</mime-mapping>
</web-app>
FileUploadManagedBean.java
package com.journaldev.prime.faces.beans;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import javax.faces.bean.RequestScoped;
import org.primefaces.model.UploadedFile;
@ManagedBean
@RequestScoped
public class FileUploadManagedBean {
UploadedFile file;
public UploadedFile getFile() {
System.out.println("getFile()");
return file;
}
public void setFile(UploadedFile file) {
System.out.println("setFile()");
this.file = file;
}
public String dummyAction(){
System.out.println("Uploaded File Name Is " + file.getFileName());
//System.out.println("Uploaded File Name Is :: "+file.getFileName()+" :: Uploaded File Size :: "+file.getSize());
return "";
}
}
javax.faces.FacesException: Error calling action method of component with id j_id_5:__9
at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:119)
at javax.faces.component.UICommand.broadcast(UICommand.java:120)
at javax.faces.component.UIViewRoot._broadcastAll(UIViewRoot.java:1013)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:284)
at javax.faces.component.UIViewRoot._process(UIViewRoot.java:1302)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:745)
at org.apache.myfaces.lifecycle.InvokeApplicationExecutor.execute(InvokeApplicationExecutor.java:38)
at org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:170)
at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:117)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:197)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:79)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:662)
Caused by: org.apache.myfaces.view.facelets.el.ContextAwareELException: javax.el.ELException: java.lang.NullPointerException
at org.apache.myfaces.view.facelets.el.ContextAwareTagMethodExpression.invoke(ContextAwareTagMethodExpression.java:108)
at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:72)
... 29 more
Caused by: javax.el.ELException: java.lang.NullPointerException
at org.apache.el.parser.AstValue.invoke(AstValue.java:268)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)
at org.apache.myfaces.view.facelets.el.ContextAwareTagMethodExpression.invoke(ContextAwareTagMethodExpression.java:96)
... 30 more
Caused by: java.lang.NullPointerException
at com.journaldev.prime.faces.beans.FileUploadManagedBean.dummyAction(FileUploadManagedBean.java:24)
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 org.apache.el.parser.AstValue.invoke(AstValue.java:262)
在我的浏览器中，它显示javax.el.ELException：java.lang.NullPointerException。可以请一个帮助找出错误