jQuery autocomplete UI with servlet is not returning any data
I have been fiddling with this code fragment from past few hours but I am unable to understand how jQuery's autocomplete UI works. I followed this tutorial http://viralpatel.net/blogs/tutorial-create-autocomplete-feature-with-java-jsp-jquery/ I used same example but instead of sending request to a JSP, I used a servlet. The request reaches the servlet "Fetcher", it executes as well but nothing is returned to the page. Here's the code.
public class Fetcher extends HttpServlet {
[...]
List<String> countryList = new ArrayList<String>();
String param = request.getParameter("term");
countryList.add("USA");
countryList.add("Pakistan");
countryList.add("Britain");
countryList.add("India");
countryList.add("Italy");
countryList.add("Ireland");
countryList.add("Bangladesh");
countryList.add("Brazil");
countryList.add("United Arab Emirates");
PrintWriter out = response.getWriter();
response.setContentType("text/plain");
response.setHeader("Cache-Control", "no-cache");
for(String country : countryList){
out.println(country);
}
[...]
}
Javascript fragment in HTML:
<script>
$(function() {
$( "#tags" ).autocomplete({
source: "Fetcher"
});
});
</script>
HTML form:
<label for="tags">Tags: </label>
<input id="tags" />
The examples on the page seems written for a pro in jquery, http://jqueryui.com/autocomplete/#default . Please, could someone tell how exactly it works, so that I can use it in other places.
The servlet should return the autocomplete data as JSON. There a several options, I have opted for an array which contains an object with label/value properties:
@WebServlet("/autocomplete/*")
public class AutoCompleteServlet extends HttpServlet {
@Override
protected void doPost(final HttpServletRequest request,
final HttpServletResponse response) throws ServletException,
IOException {
final List<String> countryList = new ArrayList<String>();
countryList.add("USA");
countryList.add("Pakistan");
countryList.add("Britain");
countryList.add("India");
countryList.add("Italy");
countryList.add("Ireland");
countryList.add("Bangladesh");
countryList.add("Brazil");
countryList.add("United Arab Emirates");
Collections.sort(countryList);
// Map real data into JSON
response.setContentType("application/json");
final String param = request.getParameter("term");
final List<AutoCompleteData> result = new ArrayList<AutoCompleteData>();
for (final String country : countryList) {
if (country.toLowerCase().startsWith(param.toLowerCase())) {
result.add(new AutoCompleteData(country, country));
}
}
response.getWriter().write(new Gson().toJson(result));
}
}
to return the autocomplete data, you could use this helper class:
class AutoCompleteData {
private final String label;
private final String value;
public AutoCompleteData(String _label, String _value) {
super();
this.label = _label;
this.value = _value;
}
public final String getLabel() {
return this.label;
}
public final String getValue() {
return this.value;
}
}
so in the servlet, the real data is mapped into a form suitable for jQuery's autocomplete. I have selected Google GSON to serialize the result as JSON.
Related:
As for the HTML document (implemented in a .jsp), pick the correct libraries, stylesheets and styles:
<html>
<head>
<script type="text/javascript" src="http://code.jquery.com/jquery-1.10.2.js"> </script>
<script type="text/javascript" src="http://code.jquery.com/ui/1.10.3/jquery-ui.js"> </script>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.10.2/themes/smoothness/jquery-ui.css" />
<script type="text/javascript" src="autoComplete.js"> </script>
</head>
<body>
<form>
<div class="ui-widget">
<label for="country">Country: </label>
<input id="country" />
</div>
</form>
</body>
</html>
Related: jQuery autocomplete demo
I have put the Javascript functions in a separate file autoComplete.js :
$(document).ready(function() {
$(function() {
$("#country").autocomplete({
source: function(request, response) {
$.ajax({
url: "/your_webapp_context_here/autocomplete/",
type: "POST",
data: { term: request.term },
dataType: "json",
success: function(data) {
response(data);
}
});
}
});
});
});
The autocomplete function uses an AJAX request to call the servlet. As the result of the servlet is suitable, it can be used as-is for the response.
Related: