Override Spring-Boot's GsonAutoConfiguration with custom Gson - spring-boot

Question

Is there a way to override the GsonAutoConfiguration in spring-boot?
I would like to add some typeAdapter to the gson instance.
Preferably using java configurations
I've added the following to the application.properties.
spring.http.converters.preferred-json-mapper=gson
and the following class
#Configuration
#ConditionalOnClass(Gson.class)
public class GsonConfig {
#Bean
public Gson gson() {
return new GsonBuilder()
.registerTypeAdapter(DateTime.class, new DateTimeTypeAdapter())
.setPrettyPrinting().create();
}
}
I am also using Jersey in the mix as well.
So I've also have the following code, which also didn't work.
InternalApplication.java
import com.google.gson.GsonBuilder;
import java.util.HashSet;
import java.util.Set;
import javax.ws.rs.core.Application;
import org.immutables.gson.stream.GsonMessageBodyProvider;
import org.immutables.gson.stream.GsonProviderOptionsBuilder;
import org.joda.time.DateTime;
public class InternalApplication extends Application {
#Override
public Set<Class<?>> getClasses() {
final Set<Class<?>> classes = new HashSet<>();
classes.add(TestResource.class);
return classes;
}
#Override
public Set<Object> getSingletons() {
final Set<Object> singletons = new HashSet<>();
singletons.add(new GsonMessageBodyProvider(
new GsonProviderOptionsBuilder()
.gson(new GsonBuilder()
.registerTypeAdapter(DateTime.class, new DateTimeTypeAdapter())
.setPrettyPrinting()
.create())
.lenient(true)
.build()
)
);
return singletons;
}
}

Answer 1

Since when does Gson have anything to with Jersey in Spring Boot? It doesn't. What you really want to do is first disable Jackson (which is the default provider). Then you can register your GsonMessageBodyProvider.
Basically all you need to do is exclude the Jackson provider from your Maven/Gradle dependencies, as the Jersey starter pulls it in
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jersey</artifactId>
<exclusions>
<exclusion>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</exclusion>
<exclusion>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-json-jackson</artifactId>
</exclusion>
</exclusions>
</dependency>
And I'm not quite sure why you are using an Application class, as Spring Boot doesn't support that for its auto-configuration. You should be using a ResourceConfig class
#Component
#ApplicationPath("/api")
public class JerseyConfig extends ResourceConfig {
public JerseyConfig() {
register(TestResource.class);
register(new GsonMessageBodyProvider(...));
}
}