apache.commons.FileUpload: parseRequest()-Method changes Request-Object?

[Daniel Haupt]

Hi folks,

i've got a problem within my struts application. I've added a filter which is triggered before the request is taken to the struts ActionForm.

I've got a multipart/form-data html formular, so I use apache.commons.FileUpload to parse the request and get my specific request parameter by using the parseRequest(HttpServletRequest)-method of ServletFileUpload class.

By doing filter.chain() I continue processing, but now I've got a nullpointer in my ActionForm because there are no more parameters in the HttpServletRequest-Object.

Is parseRequest() changing my object in any way? Are there any alternatives if I just want to get a parameter value (html-input) inside of my filter?

Thanks for your help

Daniel
[ October 20, 2008: Message edited by: Bear Bibeault ]

[Steve Luke]

Originally posted by Daniel Haupt:
Hi folks,

i've got a problem within my struts application. I've added a filter which is triggered before the request is taken to the struts ActionForm.

I've got a multipart/form-data html formular, so I use apache.commons.FileUpload to parse the request and get my specific request parameter by using the parseRequest(HttpServletRequest)-method of ServletFileUpload class.

By doing filter.chain() I continue processing, but now I've got a nullpointer in my ActionForm because there are no more parameters in the HttpServletRequest-Object.

Is parseRequest() changing my object in any way? Are there any alternatives if I just want to get a parameter value (html-input) inside of my filter?

Thanks for your help

Daniel

What do you mean by 'there are no more parameters'?

One option would be to write an HttpServletRequestWrapper implementation that takes the list of FileItems created by the parseRequest method and make them visible as parameters to all callers. You would then wrap the original request and pass the new wrapper on to filter.doChain().

public class FileUploadRequestWrapper extends HttpServletRequestWrapper
{
    private final Map<String, String[]> params;
 
    public FileUploadRequestWrapper(HttpServletRequest request, List fileItems)
    {
        super(request);
 
        HashMap<String, Object> map = new HashMap<String, Object>();
        for (Iterator fileIter = fileItems.iterator(); fileIter.hasNext();)
        {
            FileItem item = (FileItem) fileIter.next();
            if (item.isFormField())
            {   //Store values in list since each param may have 1+ values
                List<String> currentValues =
                        (List<String>) map.get(item.getFieldName());
                if (currentValues == null)
                {
                    currentValues = new ArrayList<String>();
                    map.put(item.getFieldName(), currentValues);
                }
                currentValues.add(item.getString());
            }
        }
 
        //Convert lists to arrays so we can return them as such later
        for (Map.Entry<String, Object> parameter : map.entrySet())
        {
            List<String> valueList = (List<String>) parameter.getValue();
            this.params.put(parameter.getKey(), valueList
                    .toArray(new String[valueList.size()]));
        }
 
        //Make params safe from later corruption
        this.params = Collections.unmodifiableMap(this.params);
    }
 
    public String getParameter(String paramName)
    {
        String[] values = this.params.get(paramName);
        return (values == null) ? null : values[0];
    }
 
    public Map getParameterMap()
    {
        return this.params; // safe because it is unmodifiable
    }
 
    public Enumeration getParameterNames()
    {
        return Collections.enumeration(this.params.keySet());
    }
 
    public String[] getParameterValues(String paramName)
    {
        String[] values = this.params.get(paramName);
        String[] output = null;
        if (values != null)
        {
            output = Arrays.copyOf(values, values.length);
        }
        return values;
    }
}

- Edit - Stupid smilies...
[ October 20, 2008: Message edited by: Steve Luke ]

[Bear Bibeault]

The getParameter() methods should not be used when submitting a multi-part form. The whole purpose of the commons library is to parse the multi-part request for you. So yes, it changes the request by reading its input stream so it can gather the uploaded file(s) as well as the other request parameters.

Use the API of the upload package to obtain the values. No need for a wrapper.
[ October 20, 2008: Message edited by: Bear Bibeault ]