Struts2, problem with file upload?

[ritesh_163]

hello,
I am using struts 2.2.1 framework with jdk 1.6 and running in tomcat 7. In my web application, I want to upload excel file and read the content of that file. I have searched many websites and even apache website as well but I could not solve my problem.

After uploading file, when I try to read the uploaded file, error occurs : java.lang.NullPointerException. I think the variable "upload" in java file, should automatically initialized after file upload. isn't it?

I think my code is good, but its not working.

upload page: upload.jsp

    ......  
     <s:form action="processUpload" method="post" namespace="/" enctype="multipart/form-data">  
                <s:file name="upload" label="Upload File"></s:file>  
                <s:submit label="Submit" />  
            </s:form>  
    .....

struts.xml

    ......  
            <action name="processUpload" class="action.ProcessUploadAction">  
                <interceptor-ref name="basicStack" />  
                <interceptor-ref name="fileUpload">  
                    <param name="allowedTypes">application/ms-excel,application/vnd.ms-excel,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet</param>  
                </interceptor-ref>  
                <result name="input">upload.jsp</result>  
                <result name="success">upload.jsp</result>  
                <result name="error">upload.jsp</result>  
            </action>  
    ......

ProcessUploadAction.java

    ....  
    private File upload;  
        private String uploadContentType;   
        private String uploadFileName;   
      
        public void setUpload(File upload) {  
            this.upload = upload;  
        }  
      
        public void setUploadContentType(String uploadContentType) {  
            this.uploadContentType = uploadContentType;  
        }  
      
        public void setUploadFileName(String uploadFileName) {  
            this.uploadFileName = uploadFileName;  
        }  
      
        public String execute() {  
            try{  
                System.out.println("File name:"+upload);  
            }catch(Exception ex){  
                ex.printStackTrace();  
           }  
            return SUCCESS;  
        } 
....

Output:
File name:null
java.lang.NullPointerException

can anyone suggest me, what is the problem?

Thank you in advance.

[Tolls]

What does the file upload interceptor do?
What happens if you remove it from the stack?

Indeed, I'd pare this right back to simply trying to upload the file, then start adding bits in to see what breaks.

[ritesh_163]

it worked, after changing configuration at struts.xml. I used default stack in interceptor.

[Tolls]

OK.
SO the fileUpload interceptor was the problem?