dap4/d4servlet/src/main/java/dap4/servlet/DapController.java
protected void
    senderror(DapRequest drq, int httpcode, Throwable t)
            throws IOException
    {
        if(httpcode == 0) httpcode = HttpServletResponse.SC_BAD_REQUEST;
        ErrorResponse err = new ErrorResponse();
        err.setCode(httpcode);
        if(t == null) {
            err.setMessage("Servlet error: " + drq.getURL());
        } else {
            StringWriter sw = new StringWriter();
            PrintWriter p = new PrintWriter(sw);
            t.printStackTrace(p);
            p.close();
            sw.close();
            err.setMessage(sw.toString());
        }
        err.setContext(drq.getURL());
        String errormsg = err.buildXML();
        drq.getResponse().sendError(httpcode, errormsg);
    }
protected void
    senderror(DapRequest drq, int httpcode, Throwable t)
            throws IOException
    {
        if(httpcode == 0) httpcode = HttpServletResponse.SC_BAD_REQUEST;
        ErrorResponse err = new ErrorResponse();
        err.setCode(httpcode);
        if(t == null) {
            err.setMessage("Servlet error: " + drq.getURL());
        } else {
            StringWriter sw = new StringWriter();
            PrintWriter p = new PrintWriter(sw);
            t.printStackTrace(p);
            p.close();
            sw.close();
            err.setMessage(sw.toString());
        }
        err.setContext(drq.getURL());
        String errormsg = err.buildXML();
        drq.getResponse().sendError(httpcode, errormsg);
    }
Generate an error based on the parameters

@param drq      DapRequest
@param httpcode 0=>no code specified
@param t        exception that caused the error; may be null
@throws IOException