A short document about (de-)serialization of JSON using the JSON-B API. (See also JSON on Wikipedia for a good introduction, JSON Processing for manipulation of JSON content.)
If you use Java SE, you need to add the required dependencies (jakarta.json-api, jakarta.json, jakarta.json.bind-api, yasson).
pom.xml<dependency>
<groupId>jakarta.json</groupId>
<artifactId>jakarta.json-api</artifactId>
<version>2.1.0</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>jakarta.json</artifactId>
<version>2.0.1</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>jakarta.json.bind</groupId>
<artifactId>jakarta.json.bind-api</artifactId>
<version>2.0.0</version>
</dependency>
<dependency>
<groupId>org.eclipse</groupId>
<artifactId>yasson</artifactId>
<version>2.0.4</version>
<scope>runtime</scope>
</dependency>If you use Java EE 8, this is already provided by your application server.
(This example uses the try-with-resources syntax.)
The following rules apply in case of default mapping (thus with no customization) and for most usual cases (fields are not public, for example).
Deserialization of a class uses its public or protected no-argument constructor, which must exist.
Only public getter methods, for serialization (setters for deserialization) are considered and used, irrespective of whether a corresponding field exist.
A transient field is ignored, even if matching input name-value pair.
Deserialization into Collection is supported; into other interfaces, is not supported.
Serialization follows the lexicographical order of properties.
Use @JsonbTransient for not processing a property. Annotating the field takes effect for both serialization and deserialization. Annotating the getter (setter) takes effect only for serialization (deserialization).
Use @JsonbPropertyOrder on the class for overriding the order of processing of properties.
Use @JsonbCreator to annotate the constructor or static factory method that deserialization should use, use @JsonbProperty on each parameter to map JSON names to parameters (otherwise “the proper mapping is NOT guaranteed”).
Implement JsonbAdapter to customize the mapping for a given type. Register it on the Json-B instance with JsonbConfig::withAdapters or annotate the related type with @JsonbTypeAdapter.
Implement JsonbSerializer in order to serialize an original type using a provided JsonGenerator; and similarly JsonbDeserializer using a provided JsonParser. Register those instances with JsonbConfig::withSerializers and JsonbConfig::withDeserializers or annotate the related type with @JsonbSerializer or @JsonbDeserializer.