I have a simple json object.
{"id": 1, "name": "John"}
My class for reading this object is the following.
@Getter
public class Foo {
@Setter
private long id;
@NotNull
private String name;
}
I am using lombok for generating the getters and annotating not-null fields with jetbrain's @NotNull annotation.
String json = "{\"id\": 1, \"name\": \"John\"}";
Foo foo = new Gson().fromJson(json, Foo.class);
foo.setId(42);
Reading the json works just fine.
The only problem that I have that I am getting an error from the IDE Not-null fields must be initialized from my name field.
It is technically correct, my name field is not initalized in the constructor.
However, I am using Gson to deserialize my object and know that name is never null. I do not want to create a normal object, just read from json.
Also I need the annotation @NotNull, because lomboks @Getter will generate me a getter with an @NotNull annotation.
I also have some cases where I want to replace one of my field (id) with another value.
I do not want to use a plain Java getter or remove the annoation from my attribute.
What can I do?
This solution works with Java 14 or higher.
One possible way is using a record. Instead of writing a class and generating the getter via lombok, it is also possible to do this:
public record Foo(int id, @NotNull String name) {
}
It will automatically generate a method name() which has the @NotNull annotation.
If you later need to set a field of a record, you need to follow this solution and do something like this:
public record Foo(int id, @NotNull String name) {
@NotNull
public Foo withId(int id) {
return new Foo(id, name());
}
}
This will allow to modify the id later. Only disadvantage is that you need to type out the method to set the field (withId) and that you have a new record that you need to handle correctly.
Foo foo = new Gson().fromJson(json, Foo .class);
foo = foo.withId(42);