Enable json serialization of Multimap in Spring Boot Project - json

Question

I want to serialize some google guava Multimap in a spring boot application.
public class SomeDTO {
#JsonProperty
Multimap<A, B> prop = HashMultimap.create();
}
Without using a customized jackson serializer, I get some result like
{
   "prop ":
   {
       "empty": false
   }
}
Which is definitley not what I seek to get. I thought of something like:
{
"nodes": {
"key0": [
{
"prop0": 2,
"prop1": 4
},
{
"prop0": 5,
"prop1": 6
}
],
"key1": [
{
"prop0": 23,
"prop1": 0
}
]
}
}
Adding
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-guava</artifactId>
<version>${jackson.version}</version>
</dependency>
to the pom.xml seems not sufficient... However, I'm just starting with this whole spring // pivotal universe, so I guess I miss something obvious.

Answer 1

The solution i came up with is simply adding a #Bean to my main #Configuration:
import com.fasterxml.jackson.databind.Module;
import com.fasterxml.jackson.datatype.guava.GuavaModule;
// More-obvious imports missing
#Configuration
#EnableAutoConfiguration
#ComponentScan
public class Application extends SpringBootServletInitializer {
public static void main(final String[] args) {
SpringApplication.run(Application.class, args);
}
#Override
protected final SpringApplicationBuilder configure(final SpringApplicationBuilder application) {
return application.sources(Application.class);
}
#Bean
ObjectMapper customizeJacksonConfiguration() {
ObjectMapper om = new ObjectMapper();
om.registerModule(new GuavaModule());
return om;
}
}
Afaik, the ObjectMapper Bean approach has one drawback: Everytime an ObjectMapper is created this way, all previous configuration gets thrown away.
If you want to add a module to jackson - instead of overriding previous configuration, this approach is better:
import com.fasterxml.jackson.databind.Module;
import com.fasterxml.jackson.datatype.guava.GuavaModule;
// More-obvious imports missing
#Configuration
#EnableAutoConfiguration
#ComponentScan
public class Application extends SpringBootServletInitializer {
public static void main(final String[] args) {
SpringApplication.run(Application.class, args);
}
#Override
protected final SpringApplicationBuilder configure(final SpringApplicationBuilder application) {
return application.sources(Application.class);
}
#Bean
public Module guavaModule() {
return new GuavaModule();
}
}