Identifying each field in Multiple File upload

When trying to upload multiple files with Struts 2 using ArrayList, how to identify each field?

For example, if I have two file fields, File1 and File2 and on the client side, I choose to upload only File2, Struts 2 only creates one element in the list and I am not able to correctly map File1 as empty and File2 with the uploaded file.

Is there any identifier I can use here?

Answer

Use a List (or Map) of a custom object, containing your File, the fileName and the contentType (and eventually other fields). An JSP row corresponding element, to be clear.

I did like that (because I had many other fields too) and it works like a charm.

(this is not the only way, it is just one of the working ways that will become even more handy when you will need to handle additional fields too)

POJO

public class MyCustomRow implements Serializable {

    private File   fileUpload;
    private String fileUploadFileName; 
    private String fileUploadContentType;

    private String otherField1;
    private String otherField2;

    /* All Getters and Setters here */
}

in Action

private List<MyCustomRow> rows;
/* Getter and Setter ... */

in JSP

<s:iterator value="rows" status="row">

    <s:file      name="rows[%{#row.index}].fileUpload" />

    <s:textfield name="rows[%{#row.index}].otherField1"/>
    <s:textfield name="rows[%{#row.index}].otherField2"/>

</s:iterator>

File name and content-type will be automatically detected and populated by Struts2 (ensure you have FileUploadInterceptor in your stack).