How do I pass an array to a Spring controller method with jquery ajax

Question

Here's my ajax call:

 $.ajax({
     type: 'GET',
     url: contextPath + '/test/location',
     data: {'objectValues': object.objectValues },
     datatype: 'json',
     success: function( data ) {
     var obj = jQuery.parseJSON( data );
     }
   });

it gives me this URL:

http://localhost:8080/test/location?objectValues[]=1234567890&objectValues[]=0987654321

My Spring method signature looks like this:

@RequestMapping(value = "/location", method=RequestMethod.GET)
    public @ResponseBody String loadLocation(@RequestParam(value="objectValues", required=false) String[] objectValues)

Why do I keep getting null for the value of objectValues?

Answer 1

Try changing your RequestParam annotation value to this:

@RequestParam(value="objectValues[]", required=false)

If this solves the problem, then it is due to a parameter naming incompatibility between Spring and jQuery, where jQuery wants to put square brackets in to indicate that a parameter is an array (I think PHP likes this too), but where Spring doesn't care. To see the reverse try setting the "data" parameter of the ajax request to the string: 'objectValues=1234567890&objectValues=0987654321'

Answer 2

There are multiple ways to do this, depending on which component you think is sending or receiving data in the incorrect format (or which component you have access to modify).

If you believe the default way that jQuery sends data is correct, modify your controller appropriately (note you'll need to change both on the method signature and the annotation if you use both):

@RequestMapping(value = "/location", method=RequestMethod.GET, params="objectValues[]")  
public @ResponseBody String loadLocation(@RequestParam(value="objectValues[]", required=false) String[] objectValues) {  
    ...  
}

If you believe Spring functions correctly, but data sent from jQuery is incorrect, modify jQuery:

$.ajax({
    traditional: true,
    ...  
});

See more on jQuery AJAX settings for the traditional setting.

I myself think it is cleaner to modify the way jQuery sends data; it keeps my Controller syntax looking like I want.