| name | jackson-3 |
| description | Work with Jackson 3 JSON in Spring Boot 4 — the new tools.jackson packages, auto-configured JsonMapper, ISO-8601 date defaults, immutable builder config, and @JsonView hierarchies for response shaping. Use whenever a task in a Boot 4 project touches JSON serialization/deserialization config — customizing the mapper, date/enum formatting, filtering fields per endpoint, fixing com.fasterxml.jackson imports, or "different fields for summary vs detail" — even if the user never mentions a version (check the build file). Do NOT use for choosing REST client vs server code, or for Boot 3.x Jackson 2 setups (that is the legacy this replaces). |
Jackson 3 (Spring Boot 4)
Baseline: Spring Boot 4.0+, Spring Framework 7.0+, Java 17+ (25 recommended).
Boot 4 ships Jackson 3. Two things Claude gets wrong: (1) it imports
com.fasterxml.jackson.* and configures a mutable ObjectMapper — Jackson 3 moved to the
tools.jackson.* packages with an immutable, builder-based JsonMapper; (2) it expects numeric
timestamp dates — Jackson 3 defaults to ISO-8601 strings.
When to use / not use
Use for JSON config and response shaping in Boot 4. Do NOT use for client-vs-server design
questions, or to re-teach a Boot 3.x Jackson 2 mapper (see Legacy).
What changed
| Jackson 2 (Boot 3.x) | Jackson 3 (Boot 4) |
|---|
| Packages | com.fasterxml.jackson | tools.jackson (annotations stay com.fasterxml.jackson.annotation) |
| Core type | ObjectMapper (mutable) | JsonMapper (immutable, built via builder) |
| Dates | numeric timestamp | ISO-8601 string |
| Exceptions | checked | unchecked (better in lambdas/streams) |
Spring auto-configures a JsonMapper bean — inject it; don't new one. Customize via
spring.jackson.* properties or a JsonMapper.Builder customizer bean.
spring.jackson.serialization.indent-output=true
# Migrating? use-jackson2-defaults=true restores Jackson 2 behavior (default is false = Jackson 3 defaults)
Response shaping with @JsonView (avoid DTO sprawl)
Instead of a DTO per view, define a view hierarchy and annotate fields once:
public class Views {
public interface Summary {}
public interface Public extends Summary {}
public interface Internal extends Public {}
}
public record Donut(
@JsonView(Views.Summary.class) Long id,
@JsonView(Views.Summary.class) String name,
@JsonView(Views.Public.class) String description,
@JsonView(Views.Public.class) BigDecimal price,
@JsonView(Views.Internal.class) Integer stockCount,
@JsonView(Views.Internal.class) LocalDateTime createdAt
) {}
@RestController
@RequestMapping("/api/donuts")
class DonutController {
@GetMapping @JsonView(Views.Summary.class) List<Donut> summary() { ... }
@GetMapping("/public") @JsonView(Views.Public.class) List<Donut> publik() { ... }
@GetMapping("/internal")@JsonView(Views.Internal.class) List<Donut> internal() { ... }
}
Gotchas
@JsonView annotations are still com.fasterxml.jackson.annotation.JsonView — only the
databind/core packages moved to tools.jackson. Don't "fix" the annotation import.- Jackson 3 databind ships with a compatibility bridge (3.0.x databind + jackson-annotations 2.20),
so existing annotations keep working.
- For client-side request filtering, Jackson 3's
hint() replaces wrapping returns in
MappingJacksonValue.
- Inject the auto-configured
JsonMapper; constructing your own bypasses Spring's settings and
registered modules.
Legacy (Spring Boot 3.x) — Jackson 2
import com.fasterxml.jackson.databind.ObjectMapper;
@Bean ObjectMapper objectMapper() { return new ObjectMapper().registerModule(new JavaTimeModule()); }
Boot 4: drop the manual ObjectMapper; rely on the auto-configured tools.jackson.json.JsonMapper
and spring.jackson.* properties. Set spring.jackson.use-jackson2-defaults=true only as a
temporary bridge if old timestamp behavior is required.
References
