Javascript map from java map

Question

I want to create a javascript map from a java map to set a dropdown value depending upon the value selected in another dropdown. Below is the code(not working):

var categoryAndReportsMap = new Object();
<% 
Map<String,Set<String>> categoryAndReportsJ = (Map<String,Set<String>>)      request.getAttribute("categoryAndReports");
for(Map.Entry<String,Set<String>> e : categoryAndReportsJ.entrySet()){ %>
categoryAndReportsMap[ <% e.getKey(); %> ] = <% e.getValue(); %>;
<% } %>

Please suggest how can I achieve this.

@dystroy: the : vs = is absolutely not the problem here. The OP just neglected to look at JSP-generated output in webbrowser in order to see the trivial mistake. All those Java variables are namely been printed as JS variable names instead of as JS strings. — BalusC
– BalusC, Commented May 6, 2013 at 14:24
I voted up SLaks comment, but If you are interested and to give some information to try to understand how it works, as long as I know from javascript, maps doesn't exist. Instead you have associative arrays that works similar. Key => value. Eg. var asocArray = new Array(); asocArray["a"] = "a";... — DaGLiMiOuX
– DaGLiMiOuX, Commented May 6, 2013 at 14:26
Actually, JavaScript has neither maps nor associative arrays. When you assign string-keyed values to an Array, you're actually creating named properties on the array object itself, the same as if you were doing it on a new Object() instead of a new Array(). This becomes important when you try to iterate the values back out; using for...in syntax will net you all of the custom properties as well as "count", etc. — Adrian
– Adrian, Commented May 6, 2013 at 14:28

Denys Séguret · Accepted Answer · 2013-05-06 14:25:40Z

3

You need quotes around the keys and values :

categoryAndReportsMap["<%= e.getKey() %>"] = "<%= e.getValue() %>";

But this supposes those strings don't contain quotes themselves. The best solution would be to use a JSON serializer like the excellent gson, this would be as simple as

var categoryAndReportsMap = <%= gson.toJson(categoryAndReportsJ) %>;

answered May 6, 2013 at 14:25

Denys Séguret

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3 Comments

BalusC Over a year ago

Note that this construct would still fail when the Java variable contains a doublequote or even just a newline or backslash. That's exactly why a JSON serializer is strongly recommended as a decent one already takes this into account.

Pravat Panda Over a year ago

@dystroy Thanks for the solution....Can you please suggest how to populate the values using categoryAndReportsMap in a dropdown. I tried document.getElementById('selected_report').value = categoryAndReportsMap[reportCategory]; but its not working. reportCategory is the key

Pravat Panda Over a year ago

to populate the values we need to create an array in javascript and populating the array by parsing the java object.

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