Spring Boot - Get Data from DB and store it in list and parse it to JSON using jackson

Question

I'm trying to get data from multiple tables and put it in Array List of class, and then convert it to JSON Object. But when i'm trying to parse it to json using Jackson Object Mapper all the lists are converted as below Using ObjectMapper().writeValueAsString for deserialization from class objects to json

```{
"College": [
{
"institution": [
                {
                    "instId": "T34",
                    "Country": "India",
                    "Code": "T33"
                },
                {
                    "instId": "T22",
                    "Country": "India",
                    "Code": "T22"
                }
                ],
"Rating": [
                {
                    "star": "4"
                    "comments": "good"
                },
                {
                    "star": "2"
                    "comments": "ok"
                },
}
]
}```

But i want the result as below

{
"College": [
{
"institution": [
                {
                    "instId": "T34",
                    "Country": "India",
                    "Code": "T33"
                }
                ],
"Rating": [
                {
                    "star": "4"
                    "comments": "good"
                }
            ]

},
{
"institution": [
                {
                    "instId": "T22",
                    "Country": "India",
                    "Code": "T22"
                }
                ],
"Rating": [
                {
                    "star": "2"
                    "comments": "ok"
                }
            ]

}
]
}

The above is just an example.

Please help in getting the desired output.

Below are the class files used.

public class AllCollege{
List<College> college = new ArrayList<>();

public List<College> getCollege() {
        return college;
    }

    public void setCollege(List<College> college) {
        this.college = college;
    }

}


public class College{

private List<Institution> institution = new ArrayList<>();
private List<Rating> rating = new ArrayList<>();

    public List<Institution> getInstitution() {
        return institution;
    }

    public void setInstitution(List<Institution> institution) {
        this.institution = institution;
    }

    public List<Rating> getRating() {
        return rating;
    }

    public void setRating(List<Rating> rating) {
        this.rating = rating;
    }

}



public class Institution {

    private String instId;
    private String country;
    private String code;

    public String getInstId() {
        return instId;
    }
    public void setInstId(String instId) {
        this.instId = instId;
    }

    public String getCountry() {
        return country;
    }
    public void setCountry(String country) {
        this.country = country;
    }

    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }
}


public class Rating {

    private String star;
    private String comments;

    public String getStar() {
        return star;
    }
    public void setStar(String star) {
        this.star = star;
    }

    public String getComments() {
        return comments;
    }
    public void setComments(String comments) {
        this.comments = comments;
    }

}

Below is where the data from tables is set into ArrayList and then converted to json string.

session = sessionFactory.openSession();
String sql = "from institution";
Query<InstDto> query = session.createQuery(sql);
List<Institution> configdtoList =query.list();
College alc = new College();
alc.setInstitution(configdtoList);
.
.
.
similarly Rating table.
List<College> clist = new new ArrayList<>();
clist.add(alc);
AllCollege ac = new AllCollege();
ac.setCollege(clist);

String responseJson = new ObjectMapper().writeValueAsString(ac)

Answer 1

I have created an HashMap contains the List<AllCollege> as value and then used json parser which worked as expected.