Assuming the following class:
public class Foo {
String a, b, c, d;
// The rest of the class...
}
And a REST API controller using Springboot:
@GetMapping("/foo")
public Foo myFuntion() {
return new Foo(...);
}
Requesting /foo return this JSON:
{
"a": "...",
"b": "...",
"c": "...",
"d": "..."
}
However, I would like to return only some attributes of the Foo class, for example, only attributes a and b.
How could I do that without creating a new class?
You have two solutions
Use @JsonIgnore on the property you want to exclude
For example, You want to exclude a from serializing.(Just want to get b,c,d)
public class TestDto {
@JsonIgnore
String a;
String b;
String c;
String d;
//Getter and Setter
}
Use @JsonInclude and @JsonIgnoreProperties
Via this solution, if each of a,b,c,d is null, it will be excluded from the response.
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
public class TestDto {
String a;
String b;
String c;
String d;
//getters and setter
}
You have plenty of options
... and there are many more. I personally am very comfortable with 3rd option https://www.baeldung.com/jackson-json-view-annotation - but most straight forward and implementation independent is option 1 - so you can go for it as well.
@JsonView will be the best option to handle all attributes in controlled way.
Define a view
public class Views {
public static class Public {
}
public static class private {
}
}
Map attributes
@JsonView(Views.Public.class)
public String a;
And mark the return view
@JsonView(Views.Public.class)
@RequestMapping("/items/{id}")
public Item getItemPublic(@PathVariable int id) {
return ItemManager.getById(id);
}
Now all attributes marked with the view name will be returned.
@JsonIgnoreon it. If you need to return different sets of properties in different places useDTOs.