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Version: 2.0

GSON starter

Purpose​

This starter is making easier the use of GSON with new features.

Configuration​

# Scan package for annotated adapters or factories
regards.gson.scan-prefix=fr.cnes.regards

To avoid conflict between Jackson and GSON with SPRING, set the following property :

spring.http.converters.preferred-json-mapper=gson

Autoconfiguration​

Starter autoconfigures a GsonHttpMessageConverter automatically injected in available HTTP message converters.

Il autoconfigures a Gson instance with default adapters and filters plus the introspected ones.

How to​

Create type adapters or adapter factories​

See GSON reference project.

Register a type adapter​

Just create a class extending TypeAdapter and annotated with GsonTypeAdapter with a no arg constructor :

@GsonTypeAdapter(adapted = Your.class)
public class LinkAdapter extends TypeAdapter<Your> {
    ...
}

Register a type adapter as a component​

Just create a class extending TypeAdapter and annotated with GsonTypeAdapterBean :

@GsonTypeAdapterBean(adapted = Your.class)
public class LinkAdapter extends TypeAdapter<Your> {

    @Autowired
    private MyService service;
    ...
}

Register a type adapter factory​

Just create a class implementing TypeAdapterFactory and annotated with GsonTypeAdapterFactory with a no arg constructor.

@GsonTypeAdapterFactory
public class YourFactory implements TypeAdapterFactory {
    ...
}

Register a type adapter factory as a component​

Just create a class implementing TypeAdapterFactory and annotated with GsonTypeAdapterFactoryBean (or Component):

@GsonTypeAdapterFactoryBean
public class YourFactory implements TypeAdapterFactory {

    @Autowired
    private MyService service;
    ...
}

Work with polymorphic classes​

Register a Gsonable polymorphic factory​

Just annotate the top interface or abstract class of a hierarchical set of classes with Gsonable. Under the hood, the starter will register a dynamically created PolymorphicTypeAdapterFactory. You optionnaly can specify the discriminator name in Gsonable and the discriminator values on sub types through GsonDiscriminator.

During GSON serialization, factory will inject a discriminator property whose name is either @type@ or the specified one and the value is either the class name or the specified discriminator value.
During deserialization, factory build the target object according to its discriminator value.

Register a custom polymorphic factory​

Just create a class extending PolymorphicTypeAdapterFactory and annotated with either GsonTypeAdapterFactory or GsonTypeAdapterFactoryBean.

@GsonTypeAdapterFactory
public class YourAdapterFactory extends PolymorphicTypeAdapterFactory<YourInterface> {

    public EntityAdapterFactory() {
        super(YourInterface.class, "discriminatorName", true);
        registerSubtype(YourClass1.class, "disVal1");
        registerSubtype(YourClass2.class, "disVal2");
    }
}

Exclude field from serialization​

Just annotate field with GsonIgnore to exclude a particular field.