Trouble reading JSON from URL to java objects / storing in mysql db

Question

I'm a newbie coder having just finished a 6 month coding crash-course. I'm working on a java webapp to demonstrate my skills, and the project idea I had involves retrieving JSON data from an API, something we didn't learn about in class. I made POJOs to match the JSON, and I'm trying to parse the JSON into java objects to store in a database, however my database tables are never filled with data when I run through the app. I suspect the problem is somewhere with my method to convert the JSON but any feedback is greatly appreciated. Here's all my code I think is relevant, sorry if its TMI. I also apologize if my code is ugly, I'm a beginner... Thanks!

API returns JSON like this:

{
    "result":{
        "status":1,
        "num_results":1,
        "total_results":500,
        "results_remaining":499,
        "matches":[{
            "match_id":3188095188,
            "match_seq_num":2784956606,
            "start_time":1495079320,
            "lobby_type":7,
            "radiant_team_id":0,
            "dire_team_id":0,
            "players":[{
                "account_id":86920222,
                "player_slot":0,
                "hero_id":18
             },{
                "account_id":61122568,
                "player_slot":1,
                "hero_id":85
             },{
                "account_id":10208661,
                "player_slot":2,
                "hero_id":13
             },{
                "account_id":106083675,
                "player_slot":132,
                "hero_id":50
             }]
         }]
    }
}

My POJOs:

@Entity
@JsonIgnoreProperties(ignoreUnknown = true)
public class Result {

    @JsonIgnore
    @Id
    @GeneratedValue
    private int id;

    @JsonProperty("status")
    private int status;

    @JsonProperty("num_results")
    private int num_results;

    @JsonProperty("total_results")
    private int total_results;

    @JsonProperty("results_remaining")
    private int results_remaining;

    @OneToMany
    @JoinColumn(name = "result_id")
    @ElementCollection(targetClass=Matches.class)
    @JsonProperty("matches")
    private List<Matches> matches;

    // getters and setters 
}

@Entity
@JsonIgnoreProperties(ignoreUnknown = true)
public class Matches {

    @Id
    @JsonProperty("match_id")
    private int match_id;

    @JsonIgnore
    @ManyToOne
    private Result result;

    @JsonProperty("match_seq_num")
    private int match_seq_num;

    @JsonProperty("start_time")
    private int start_time;

    @JsonProperty("lobby_type")
    private int lobby_type;

    @JsonProperty("radiant_team_id")
    private int radiant_team_id;

    @JsonProperty("dire_team_id")
    private int dire_team_id;

    @OneToMany
    @JoinColumn(name = "Matches_id")
    @ElementCollection(targetClass=Players.class)
    @JsonProperty("players")
    private List<Players> players;

    // getters and setters
}

@Entity
@JsonIgnoreProperties(ignoreUnknown = true)
public class Players {

    @JsonIgnore
    @Id
    @GeneratedValue
    private int id;

    @JsonIgnore
    @ManyToOne
    private Matches matches;

    @JsonProperty("account_id")
    private int account_id;

    @JsonProperty("player_slot")
    private int player_slot;

    @JsonProperty("hero_id")
    private int hero_id;

    // getters and setters
}

Services method to read and convert the JSON to objects (url is censored, don't want my API key to be public)

public class SteamService {
    public static Result getMatchHistory(String steamid){
        Result result = new Result();
        String MatchHistoryUrl = "https:**URL**="+steamid;
        RestTemplate restTemplate = new RestTemplate();
        Result jsonresult = restTemplate.getForObject(MatchHistoryUrl, Result.class);
        return jsonresult;
    }
}

Controller

@Controller
@RequestMapping("")
public class HomeController {
    @Autowired
    private ResultsDao resultsDao;

    @RequestMapping(value = "", method = RequestMethod.GET)
    public String index(Model model){
        model.addAttribute("title", "Welcome");
        return "home/home";
    }

    @RequestMapping(value = "", method = RequestMethod.POST)
    public String processSteamIdField(@RequestParam("steamid")String steamid, Model model) {
        Result newresult = getMatchHistory(steamid);
        resultsDao.save(newresult);
        return "redirect:results";
    }
}

DAO

@Repository
@Transactional
public interface ResultsDao extends CrudRepository<Result, Integer>{
}

Answer 1

Maybe my approach is a bit naive, but... If you want to store the JSON as string in the database, then I would use an object mapper for this:

new ObjectMapper().writeValueAsString(myObject);

and for reading a JSON and parsing it to a class I would do:

new ObjectMapper().readValue(JSON_STRING_HERE, "utf-8"), MyPOJO.class);

Also, if you already are using Spring, then your controller may look like this (for a POST, for example)

@RequestMapping(value = "/", method = RequestMethod.POST)
public MyPojo myController(@RequestBody MyPojo myBody) {
    myRepository.save(myBody);
}

So, the parsing of the JSON that the client is sending to your app and your controller is already handled by Spring