In reference to this post at Daring Fireball - I have always reasoned that the cursor is placed at the top of the new message when you hit reply precisely because you will need to start at the top with a salutation, then work your way down through the message adding your interjections after relevant paragraphs and deleting anything which you don’t need to quote. The problem is that these days nobody bothers with that, they assume the cursor is at the top because that’s where their reply is supposed to go. The worst example is when you get sent an email with something like “What do you think we should do?” at the top, and you scroll down to realise that you’ve been sent a massive dollop of email correspondence going back three weeks, which you’re going to have to read from bottom to top before you can reply.

As my bluetooth headset seems to be a dead loss, I thought I’d take it apart to see how it was made. I did a lot of searching and I don’t think anyone has done this yet - I certainly couldn’t find any photos. P1090154.JPG

There are many web pages making grand claims for the number of problems which can supposedly be solved by using vinegar. One that I’ve read quite often is that you can prevent your car windows from icing up. For example, here’s a quote from “Chef Noah”:
Prevent ice from forming on a car windshield overnight.
Coat the window with a solution of three parts white or vinegar to one part water.
I decided to try it last night. I mixed white vinegar and water in the designated proportions, put it in a misting bottle, and sprayed it all over my windscreen and rear screen. Then I went to bed safe in the knowledge that I’d be leaping happily into my car in the morning and driving off while all my neighbours stared enviously at my frost-free car. Well, I’m not very happy to report that this morning there was absolutely no change in the amount of ice on my screen. Furthermore, I don’t even think it was a particularly cold night last night - it was only about -1°C when I went out to the car in the morning. Don’t these sites test their tips before posting them? So I got cold hands as usual. Bah.

I’m going to document this because it took me ages to work out, but in the end it turned out to be quite easy. In Rails there is a useful thing called ‘flash’. Flash is a component which is automatically available in every view. Controller classes can insert a message into the flash object, and when it renders the view it can display the message. The great thing is that by default the message exists in the flash for two requests. This is so that the current request can be terminated with a browser redirect, and when the browser follows the redirect the flash message will be there waiting for it. Read on for more details.

(Continued from part 1) Next you need a component which runs at the conclusion of every request. This component is responsible for decrementing the message counters in the flash object:
package info.evansweb.spring.examples.flash;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

 * Copyright 2007 Jon Evans,
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 * @author Jon Evans,
public class FlashDecrementer extends HandlerInterceptorAdapter {

  private Flash flash;

  public void setFlash(Flash flash) {
    this.flash = flash;

  public void decr() {
    if (flash!=null) {

  public void afterCompletion(HttpServletRequest request,
      HttpServletResponse response, Object handler, Exception exception)
      throws Exception {
It gets wired into the Spring framework in your applicationContext.xml:
  <bean id="flash" class="info.evansweb.spring.examples.flash.Flash"
    <!-- Google for aop:scoped-proxy if you don't understand why this is here  -->
    <aop:scoped-proxy />

  <bean id="flashDecrementer"
    <property name="flash" ref="flash" />
and in the servlet xml file:
  <bean id="handlerMapping"
    <property name="interceptors">
        <!-- This line makes sure the flash gets decremented
          after every request -->
        <ref bean="flashDecrementer" />

    <property name="prefix" value="/WEB-INF/jsp/" />
    <property name="suffix" value=".jsp" />
    <property name="viewClass"
      value="org.springframework.web.servlet.view.JstlView" />
    <property name="attributes">
        <!-- This is the line that makes the flash object available in
          every view -->
        <entry key="flash" value-ref="flash" />
Now, it’s really easy to add a message to the flash from your controller. First you make sure the flash object is available:
  private Flash flash;
Then in a controller method you just add your message:
  public ModelAndView login() {
    // Do your login stuff here...
    flash.setNotice("Welcome back!");

    ModelAndView mav = new ModelAndView("redirect:/");
    return mav;
And in your views you just include a simple flash.jsp file containing something like this:
<c:if test="${flash.error != null}"></c:if>
  <div class="error" id="error">${flash.error}</div>
<c:if test="${flash.notice != null}">
  <div class="notice" id="notice">${flash.notice}</div>
I’ve built an example web application and packaged it up. Once unzipped you can run it straight away with “mvn jetty:run” if you have maven2 installed. Here’s the zipfile (only 13k!): Finally a shameless plug. I quit my full-time job at the end of November 2007 in order to become a freelance developer. I’m starting a new software development business with my good friends Surjan Basan and Simon Hutchinson. Please feel free to get in touch if you need any Java, Ruby on Rails or .Net expertise. If you want to make any comments, please return to the original blog post.