I am creating a web application in java. On client side I have a bar chart that display some data stored in a tsv file created by the java server page. By clicking on a button the server updates these data in the file. Now I want to read the refreshed data, but I get the older ones. It seems that the browser cached the file so it can't get the changed file.
This is my servlet code:
public class GetDataServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
private User user;
Utility utility;
public void init() throws ServletException {
reset();
}
public void doGet (HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "no-cache");
PrintWriter out = response.getWriter();
user.getProfile().get(0).setWeigth(user.getProfile().get(0).getWeigth()+0.03);
user.getProfile().get(1).setWeigth(user.getProfile().get(1).getWeigth()+0.02);
user.getProfile().get(5).setWeigth(user.getProfile().get(5).getWeigth()+0.01);
utility.createTsvFile(user, "/usr/local/apache-tomcat-7.0.50/webapps/Visualizer/data.tsv");
String message = String.format("data.tsv");
i++;
out.print(message);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
if(request.getParameter("reset").compareTo("yes")==0)
reset();
}
private void reset(){
List<Concept> children = new ArrayList<Concept>();
Concept food = new Concept();
food.setWeigth(0.10);
food.setLabel("food");
food.setColor("#98abc5");
Concept dish = new Concept();
dish.setWeigth(0.08);
dish.setLabel("dish");
dish.setParent(food);
dish.setColor("#8a89a6");
Concept cuisine = new Concept();
cuisine.setWeigth(0.06);
cuisine.setLabel("cuisine");
cuisine.setParent(food);
cuisine.setColor("#8a89a6");
children.add(dish);
children.add(cuisine);
food.setChildren(children);
children.clear();
Concept pizza = new Concept();
pizza.setWeigth(0.05);
pizza.setLabel("pizza");
pizza.setParent(dish);
pizza.setColor("#6b486b");
Concept spaghetti = new Concept();
spaghetti.setWeigth(0.05);
spaghetti.setLabel("spaghetti");
spaghetti.setParent(dish);
spaghetti.setColor("#6b486b");
Concept sushi = new Concept();
sushi.setWeigth(0.06);
sushi.setLabel("sushi");
sushi.setParent(dish);
sushi.setColor("#6b486b");
children.add(pizza);
children.add(spaghetti);
children.add(sushi);
dish.setChildren(children);
List<Concept> profile = new ArrayList<Concept>();
profile.add(food);
profile.add(dish);
profile.add(cuisine);
profile.add(pizza);
profile.add(spaghetti);
profile.add(sushi);
user = new User("mario", profile);
utility = new Utility("");
}
}
This is the javascript code that calls the servlet:
function ajaxSyncRequest(reqURL) {
//Creating a new XMLHttpRequest object
var xmlhttp;
if (window.XMLHttpRequest) {
xmlhttp = new XMLHttpRequest(); //for IE7+, Firefox, Chrome, Opera, Safari
} else {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); //for IE6, IE5
}
//Create a asynchronous GET request
xmlhttp.open("GET", reqURL, false);
xmlhttp.send(null);
//Execution blocked till server send the response
if (xmlhttp.readyState == 4) {
if (xmlhttp.status == 200) {
document.getElementById("message").innerHTML = xmlhttp.responseText;
update(xmlhttp.responseText);
//alert(xmlhttp.responseText);
} else {
alert('Something is wrong !!');
}
}
}
function update(file){
d3.tsv(file, function(error, data) {
......
In the html page I have also put this:
<meta http-equiv="Cache-control" content="no-cache">
but it doesn't work.
With this code I can display the correct data the first time I call the servlet, than even if the data in the file tsv changes I get the first one.
Which is the best way to read the refreshed data in the file?