上傳的NullPointerException使用Struts 2

文件時，這是JSP上傳的NullPointerException使用Struts 2

<s:form action="uploadfile.action" enctype="multipart/form-data" method="POST" cssClass="bodyClass"> 
    <tr> 
     <td> 
      Image: 
     </td> 
     <td style="width: 200px;"> 
      <s:file id='image' name='uploadedfile' cssClass="formTextField" /> 
     </td> 
     <td> 
      <input type="submit" value="Upload" class="button"/> 
     </td> 
    </tr> 

</s:form>

這是Struts的.XML

<package name="upload" namespace="/upload" extends="struts-default"> 
      <action name="uploadfile" class="com.secureweb.web.upload.UploadAction"> 
       <result name="uploadImage">/pages/fileupload/uploadimage.jsp</result> 
      </action> 
    </package>

Action類

public class UploadAction extends ActionSupport { 
    private File uploadedfile; 

    public String execute() throws Exception { 
     try { 
      System.out.println(uploadedfile.getName()); 
     } catch (Exception e) { 
      System.out.println(e); 
     } 
     return "uploadImage"; 
    } 

    public File getUploadedfile() { 
     return uploadedfile; 
    } 

    public void setUploadedfile(File uploadedfile) { 
     this.uploadedfile = uploadedfile; 
    } 
}

在我的項目庫

commons-beanutils-1.7.0.jar 
    commons-lang-2.3.jar 
    displaytag-1.2.jar 
    displaytag-export-poi-1.2.jar 
    displaytag-portlet-1.2.jar 
    log4j-1.2.14.jar 
    pljava.jar 
    postgresql-8.3-603.jdbc4.jar 
    postgresql-8.3-604.jdbc3.jar 
    cos.jar 

    Struts 2 2.1.8 Basic- commons-io-1.3.2.jar 
          commons-fileupload-1.2.1.jar 
          commons-logging-1.0.4.jar 
          freemarker-2.3.15.jar 
          ognl-2.7.3.jar 
          struts2-core-2.1.8.1.jar 
          xwork-core-2.1.6.jar 
    Then there is persistance.jar of EJB 
    And there is also Hibernate Library.

沒有其他

結果爲NullPointerException，因爲屬性上傳文件爲空。文件上傳無法正常工作。爲什麼這個變量總是值爲null。我的操作系統是Ubuntu Linux 11.4，Web服務器 - Apache Tomcat 6. IDE- Netbeans。

來源

2011-11-19 Mohammed Swafvan