Question

I have this class that I persist by creating a JSON object based on its annotation:

@Entity(name = "user")
public class User { 
    @Id 
    private String id;
    @Column
    private String name;
    @Column
    private Integer age;
    public User() {}
public User(String id, String name, String age) {}
// ... code omitted
}

boolean ok = createEntity(new User("uid1", "eli", 25));

The method above will convert the User object into a Map respresenting a JSON object like:

map.put("ID", "uid1");
map.put("name", "eli");
map.put("age", 25);

This works fine. However I need to create a User object based on a response map containling values in similar form like the above, first I get the response from the server in form of JSON string:

{
    "id" : "uid2",
    "name" : "ben",
    "age" : 20
}

I mean, if I parse this JSON string into a map:

map.put("id", "uid2");
map.put("name", "ben");
map.put("age", 20);

How can I construct a User object filling the values from the map to the correct @Column field?

Update:

I know about Jackson library, but the idea here is that I need to work with annotations as I am building a library that needs classes to be annotated. I am just after the way to create object from json/map and assign the right values to the right field

Answer 1

Use the Jackson library. It converts your objects to json without the need to annotate them.