p：fileUpload为每个文件调用bean构造函数

Question

I'm trying to use <p:fileUpload> to upload a file. Here's the view:

  <h:form enctype="multipart/form-data">
     <p:growl id="messages" showDetail="true" />
     <p:fileUpload
                fileUploadListener="#{viewscopedBean.handleFileUpload}"
                mode="advanced" dragDropSupport="true" multiple="true"
                update="messages" />
  </h:form>

Bean:

@ManagedBean
@ViewScoped
public class ViewscopedBean implements Serializable{
    private List<UploadedFile> uploadedFiles; //to remember which files have been uploaded

    public ViewscopedBean() {
            super();
            System.out.println("@constructor");
            uploadedFiles = new ArrayList<UploadedFile>();
    }

    public void handleFileUpload(FileUploadEvent event) { 
           System.out.println("! HANDLE FILE UPLOAD !");
           // do something
    }  
    public List<UploadedFile> getUploadedFiles() {
            return uploadedFiles;
    }

    public void setUploadedFiles(List<UploadedFile> uploadedFiles) {
            this.uploadedFiles = uploadedFiles;
    }
} 

web.xml

<filter>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <filter-class>
        org.primefaces.webapp.filter.FileUploadFilter
    </filter-class>
    <init-param>
        <param-name>thresholdSize</param-name>
        <param-value>512000</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <servlet-name>Faces Servlet</servlet-name>
</filter-mapping>

When I click on the upload button , the progressbar is filling up to 100% (like it does something), but then the page is reloaded (constructor is being called for every uploaded file) - the handleFileUpload method is never called.

There aren't any errors or warnings, it just doesn't do what it should. I have JSF 2.0 and use Primefaces 4, maybe there is a problem?

How is this caused and how can I solve it?

Answer 1

First things first, ensure that you have commons-fileupload and its compile-time dependency commons-io on your classpath. The handler not being called suggests that you have these dependencies missing.

Since 4.0 , there is now an optional context-param which specifies the server-side engine for handling FileUpload uploads:

<context-param>
<param-name>primefaces.UPLOADER</param-name>
<param-value>auto|native|commons</param-value>
</context-param>

In the absence of the context-param , PrimeFaces otherwise selects the most appropriate uploader engine by detection.

Given that you are not using JSF 2.2 , this means that it will first select auto , and therefore will redirect to use commons .

So you can see how important it is that you have commons-fileupload and commons-io in your project.

When I copied and pasted your code into a Primefaces 3.5 project containing these dependencies, your code worked for me. The constructor was called once and only once, and the handle method was called each time I uploaded a file.

I repeated the test using 4.0 and again, the constructor was called once and only once.

Here's the configuration that I used in web.xml (needed by commons-fileupload ):

<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>

Here's the backing bean:

package uk;

import java.util.ArrayList;
import java.util.List;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

import org.primefaces.event.FileUploadEvent;
import org.primefaces.model.UploadedFile;

    @ManagedBean(name = "tempBean")
    @ViewScoped
    public class TempBean {

        private List<UploadedFile> uploadedFiles; //to remember which files have been uploaded

        public TempBean() {
                super();
                System.out.println("@constructor");
                uploadedFiles = new ArrayList<UploadedFile>();
        }

        public void handleFileUpload(FileUploadEvent event) { 
               System.out.println("! HANDLE FILE UPLOAD !");
               // do something
        }  
        public List<UploadedFile> getUploadedFiles() {
                return uploadedFiles;
        }

        public void setUploadedFiles(List<UploadedFile> uploadedFiles) {
                this.uploadedFiles = uploadedFiles;
        }

    }

Here's the page:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html lang="en" 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"
    xmlns:fn="http://java.sun.com/jsp/jstl/functions">

<h:body>

    <h:form enctype="multipart/form-data">
     <p:growl id="messages" showDetail="true" />
     <p:fileUpload
                fileUploadListener="#{tempBean.handleFileUpload}"
                mode="advanced" dragDropSupport="true" multiple="true"
                update="messages" />
  </h:form>
</h:body>
</html>

And finally here is the snippet of my POM that contains the dependencies and versions for Apache Commons:

<dependency>
        <groupId>commons-io</groupId>
        <artifactId>commons-io</artifactId>
        <version>2.2</version>
    </dependency>
    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.3</version>
    </dependency>