This work for me

@Name("uploadHandler")
@Scope(ScopeType.EVENT)
public class UploadHandler {
		
	@In(value="#{facesContext}")
	FacesContext facesContext;
	
	@Logger private Log log;
	
	
	private byte[] file;	 
	
	public void handleUpload() throws IOException{
		
		String path = ((ServletContext) facesContext.getExternalContext().getContext()).getRealPath("/my/files/dir");
		File f = new File(path,"myFile.txt");
		log.info(f);
		FileOutputStream fo = new FileOutputStream(f);
		fo.write(file);
		fo.flush();
		fo.close();
	
	}

	public byte[] getFile() {
		return file;
	}

	public void setFile(byte[] file) {
		this.file = file;
	}

}

and the form

<h:form id="fooForm" enctype="multipart/form-data">
        
           <s:fileUpload id="file" 
				data="#{uploadHandler.file}"
				accept="image/jpg"
		    />
        
            <h:commandButton id="upload" value="Upload !!" 
                             action="#{uploadHandler.handleUpload}"/>     			  
        
        </h:form>

But I don't recommand to use the ....getRealPath(/my/files/dir);.... instead use a path that you configure in seam.properties.