How to convert ArrayList<String> to JSON object using Jackson in Spring @ResponseBody

Question

Server layer will return a list of String value, like

{"Bob", "Charlotte", "Johnson", "David"...}

Now we need the List String to be a Json object to push to front end, like

[{id: "Bob"}, {id: "Charlotte"}, {id: "Johnson"}, {id: "David"...}]

or

[{name: "Bob"}, {name: "Charlotte"}, {name: "Johnson"}, {name: "David"...}]

Any label is fine, we just need a label to make it as JSON object. Does Jackson has something to convert List of String by default i.e. {string: "Bob"}? That will be really sweet......

We are using Jackson to convert lists of Objects (sometimes even Strings). By default it converts the List<String> to an array of strings by itself. As mentioned below, if you really want it to convert to an array of name/value pairs, you should return a list of objects with one String name (or id or whatever) property. — Shadow Man
– Shadow Man, Commented May 15, 2013 at 1:38
@Shadow Creeper Thanks, that's great, but if the converted array of string doesn't have a label, then how can the front end identify the value(as JSON object), especially want a label to handle list? — Dreamer
– Dreamer, Commented May 15, 2013 at 1:47
Our front end is a simple web app. We just iterate through the list. You can sort the list if you like, or add to it, remove from it, modify it. It is just an array, with a length and everything. You can do the normal for loop and reference it via resultArray[index]. — Shadow Man
– Shadow Man, Commented May 15, 2013 at 1:52

matt b · Accepted Answer · 2013-05-15 01:33:06Z

7

The easiest thing to is to make your controller method return a structure that maps exactly to the JSON you want - for example a List<SomeObject> where SomeObject is a class with a String id field.

answered May 15, 2013 at 1:33

matt b

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1 Comment

Dreamer Over a year ago

Thank you. Like you said I made an inner class with only one String field to hold the value, then made a list of this class object. Now it can be identified from front end.

Manav Dewan · Accepted Answer · 2013-05-18 12:05:45Z

1

Th way of doing this is converting you List of String into a New Map.

Code :

@ResponseBody
@RequestMapping("/mapping")
function mySpring()
{


            List<String> myStringList;
            Map<String,String> jsonMap= new LinkedHashMap<String,String>(); 
     // Use LinkedHashMap if you want to maintain order


    String key="id";        
     // Id or Name

            for (String myString: myStringList)
        {
        jsonMap.put(key,myString);

        }

return jsonMap;

}

answered May 18, 2013 at 12:05

Manav Dewan

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