Passing a Map<String,String> to a springMVC controller
ajax, json, spring, spring-mvc
Solution
Binding a map in a spring controller is supported the same way as binding an array. No special converter needed!
There is one thing to keep in mind though:
- Spring uses command object(s) as a top level value holder. A command object can be any class.
So all you need is a wrapper class (`TagsWrapper`) which holds a field of type `Map<String, String>` called tags. The same approach you take to bind an array.
This is explained pretty well in the docs but i kept forgetting the need of the wrapper object once in a while ;)
The second thing you need to change is the way you submit the tags values:
- use one form parameter per map key and not a full string representation of the complete map.
one input value should look like this:
<input type="text" name="tags[key]" value="something">
If tags is a map in a wrapper this works out of the box for form submits.
Problem
I am trying to send a HashMap or any other Map implementation from ajax to a Spring MVC controller Here's the detail of how I do it : the Ajax call is as follow ``` var tags = {}; tags["foo"] = "bar"; tags["whee"] = "whizzz"; $.post("doTestMap.do", {"tags" : tags }, function(data, textStatus, jqXHR) { if (textStatus == 'success') { //handle success console.log("doTest returned " + data); } else { console.err("doTest returned " + data); } }); ``` then on the controller side I have : ``` @RequestMapping(value="/publisher/doTestMap.do", method=RequestMethod.POST) public @ResponseBody String doTestMap(@RequestParam(value = "tags", defaultValue = "") HashMap<String,String> tags, HttpServletRequest request) { // System.out.println(tags); return "cool"; } ``` Unfortunately I systematically get ``` org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.lang.String' to required type 'java.util.Map'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [java.util.Map]: no matching editors or conversion strategy found ``` What am I doing wrong ? Thank you.