[FIXED] Spring query convert to a nested JSON structure

Issue

I'm new to spring and Java and trying to figure out how to go about formatting the json response into the desired structure.

I have a spring query that's returning 2 columns from a table like below which are really the key and values I need for the json structure:

class="s-table-container">

Names	Values
Car	Toyota
Bike	Schwinn
Scooter	Razor
A0	11
A1	12
A2	13
B0	2000
B1	4000
B2	22000

The current json output from the controller is this:

[{
        "names": "Car",
        "values": "Toyota"
    },
    {
        "names": "Bike",
        "values": "Schwinn"
    },
    {
        "names": "Scooter",
        "values": "Razor"
    },
    {
        "names": "A0",
        "values": "11"
    },
    {
        "names": "A1",
        "values": "12"
    },
    {
        "names": "A2",
        "values": "13"
    },
    {
        "names": "B0",
        "values": "2000"
    },
    {
        "names": "B1",
        "values": "4000"
    },
    {
        "names": "B2",
        "values": "22000"
    }
]

And the desired json format is this where the table column names are removed and instead json structure is created using the names column for the keys:

{
    "Car": "Toyota",
    "Bike": "Schwinn",
    "Scooter": "Razor",
    "Data": [{
        "A0": "11",
        "B0": "2000"
    }, {
        "A1": "12",
        "B1": "4000"
    }, {
        "A2": "13",
        "B2": "22000"
    }]
}

Repository

   @Query (value = "Select names, values ... :id")
    List<Data> findData(@Param("id") Long id) ;

      interface Data {
        String getnames();
        String getvalues();
    }

Service

    public List<Data> getData(Long id) {return repo.findData(id);}

Controller

    @GetMapping("/getdata/{id}")
    public ResponseEntity<List<Data>> getData(@PathVariable Long id) {
            List<Data> c = service.getData(id);
            return new ResponseEntity<>(c, HttpStatus.OK);

    }

It seems that I need to process the result set and need to loop through them to create the desired structure but not sure how to proceed with that, or perhaps there is an easier way to get to the desired structure. Any guidance would be appreciated.

Solution

So return a ResponseEntity<Map<String, Object>> instead of a List to simulate a Json object.

List<Data> c = service.getData(id);

Map<String, Object> map = new HashMap<>();
map.put("Key", "Value");
map.put("Car", c.get(0).getvalues());
map.put("Entire List", c);

return new ResponseEntity<>(c, HttpStatus.OK);

Obviously you'll have to write your own logic but it should be pretty straight forward. Or, even better, consider making a class for the object returned if you're going to be using it a lot, and just return ResponseEntity< YourCustomObject >

Answered By - Krusty the Clown
Answer Checked By - Gilberto Lyons (JavaFixing Admin)