https://github.com/sigpwned/jackson-modules-java-17-sealed-classes
Simplified polymorphic de/serialization of Java 17 sealed classes for Jackson
https://github.com/sigpwned/jackson-modules-java-17-sealed-classes
jackson java17 json sealed-class
Last synced: 6 months ago
JSON representation
Simplified polymorphic de/serialization of Java 17 sealed classes for Jackson
- Host: GitHub
- URL: https://github.com/sigpwned/jackson-modules-java-17-sealed-classes
- Owner: sigpwned
- License: apache-2.0
- Created: 2022-07-24T18:16:28.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2024-01-17T07:30:45.000Z (over 1 year ago)
- Last Synced: 2025-04-10T00:44:39.745Z (6 months ago)
- Topics: jackson, java17, json, sealed-class
- Language: Java
- Homepage:
- Size: 76.2 KB
- Stars: 18
- Watchers: 3
- Forks: 0
- Open Issues: 4
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Jackson Modules - Java 17 Sealed Classes [](https://github.com/sigpwned/jackson-modules-java-17-sealed-classes/actions/workflows/tests.yml) [](https://sonarcloud.io/summary/new_code?id=sigpwned_jackson-modules-java-17-sealed-classes) [](https://maven-badges.herokuapp.com/maven-central/com.sigpwned/jackson-modules-java17-sealed-classes)
`jackson-modules-java17-sealed-classes` is a [Jackson](https://github.com/FasterXML/jackson) module that adds improved support for polymorphic serialization of Java 17 sealed classes.
## Goals
* Add improved support for polymorphic serialization of Java 17 sealed classes
## Non-Goals
* Change any other aspects of Jackson serialization
## Usage
To activate this feature, users must register the `Jdk17SealedClassesModule` module with the `ObjectMapper`. Simply include this library, and add the module to the `ObjectMapper`:
ObjectMapper mapper=new ObjectMapper().registerModule(new Jdk17SealedClassesModule());
Without this module, sealed classes must use the `@JsonSubTypes` annotation for [polymorphic serialization](https://www.baeldung.com/jackson-annotations), just like any other class:
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
@JsonSubTypes({
@JsonSubTypes.Type(value=AlphaSealedExample.class, name="alpha"),
@JsonSubTypes.Type(value=BravoSealedExample.class, name="bravo")})
public sealed class SealedExample permits AlphaSealedExample, BravoSealedExample {
}
public final class AlphaSealedExample extends SealedExample {
private String alpha;
public String getAlpha() {
return alpha;
}
public void setAlpha(String alpha) {
this.alpha = alpha;
}
public SealedExample withAlpha(String alpha) {
setAlpha(alpha);
return this;
}
}
public final class BravoSealedExample extends SealedExample {
private String bravo;
public String getBravo() {
return bravo;
}
public void setBravo(String bravo) {
this.bravo = bravo;
}
public SealedExample withBravo(String bravo) {
setBravo(bravo);
return this;
}
}
However, this is repetitive, since sealed classes already enumerate their subtypes explicitly. With this module, users get polymorphic serialization of sealed classes by using only the `@JsonTypeInfo` annotation on the parent sealed class. Users can also add `@JsonTypeName` to child classes to customize subtype naming, but it is not required.
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
public sealed class SealedExample permits AlphaSealedExample, BravoSealedExample {
}
@JsonTypeName("alpha")
public final class AlphaSealedExample extends SealedExample {
private String alpha;
public String getAlpha() {
return alpha;
}
public void setAlpha(String alpha) {
this.alpha = alpha;
}
public SealedExample withAlpha(String alpha) {
setAlpha(alpha);
return this;
}
}
@JsonTypeName("bravo")
public final class BravoSealedExample extends SealedExample {
private String bravo;
public String getBravo() {
return bravo;
}
public void setBravo(String bravo) {
this.bravo = bravo;
}
public SealedExample withBravo(String bravo) {
setBravo(bravo);
return this;
}
}
Either example would result in the following JSON:
serialize(new AlphaSealedExample().withAlpha("value")) → {"type":"alpha","alpha":"value"}
deserialize({"type":"alpha","alpha":"value"}) → new AlphaSealedExample().withAlpha("value")
serialize(new BravoSealedExample().withBravo("value")) → {"type":"bravo","bravo":"value"}
deserialize({"type":"bravo","bravo":"value"}) → new BravoSealedExample().withBravo("value")
## Acknowledgements
Many thanks to [@shartte](https://github.com/shartte) for his work on [FasterXML/jackson-module-kotlin#239](https://github.com/FasterXML/jackson-module-kotlin/issues/239), where he implemented a very similar feature for Kotlin. And of course, thank you to [@cowtowncoder](https://github.com/cowtowncoder) for maintaining the excellent [FasterXML/jackson](https://github.com/FasterXML/jackson) library for all this time.