Struts2 getOutputStream() has already been called for this response
public String execute() throws Exception{
HttpServletResponse response = ServletActionContext.getResponse();
FileInputStream in = new FileInputStream(filePath);
sout = response.getOutputStream();
byte b[] = new byte[1024];
int len = 0;
while ((len = in.read(b)) > 0) {
sout.write(b,0,len);
}
sout.flush();
sout.close();
in.close();
return SUCCESS;
}