Convert POJO into JSON

Question

I have a POJO.

@Data
@AllArgsConstructor
@Builder
public class Emp {
    private String position;
    private String name;
}

Suppose, we have created an object

Emp emp = new Emp("Manager", "Bob");

How can I convert it to a list and save it in a database in JSON format?

The data should be stored in the database in the format below:

{
  list:[
    {
       position: Manager
       name: Bob
    }
  ]
}

Are there any ready solutions for that?

I converted an object into a list and then I called the .toString() method on it:

Collections.singletonList(emp);

But when I store it in the database, the next save goes to the database:

[Emp(position=Manager, name=Bob)]

But I need to store the record in a different way

Answer 1

How can I convert it to a list and save it in a database in JSON format?

The data should be stored in the database in the format below:

{
  "list": [
    {
       "position": "Manager"
       "name": "Bob"
    }
  ]
}

Since the serialized JSON is required to have a property "list" you can't simply serialize the List as is.

Instead, you can define a POJO wrapping this list.

That's how it might look like (I've made it generic in order to make it suitable for serializing any type of list):

@Data
@AllArgsConstructor
public static class ListWrapper<T> {
    private List<T> list;
}

And that's how it can be serialized using Jackson's ObjectMapper and ObjectWriter:

List<Emp> emps = List.of(new Emp("Manager", "Bob"));
ListWrapper<Emp> listWrapper = new ListWrapper<>(emps);
        
ObjectMapper mapper = new ObjectMapper();
ObjectWriter writer = mapper.writerWithDefaultPrettyPrinter();
        
String json = writer.writeValueAsString(listWrapper);
System.out.println(json);

Output:

{
  "list" : [ {
    "name" : "Manager",
    "position" : "Bob"
  } ]
}

Answer 2

If you need to store the object list as JSON in DB then you need Convert the list of object to JSON string using Jackson ObjectMapper. Store the converted string to DB.