retrieving vavr collection via spring data rest from mongo db doesn't work - mongodb

Question

I created a small spring boot project to retrieve a sample object from mongoDb via spring data rest which contains a Seq (vavr collection). Immediately after booting the app it doesn't work. At first I have to do an insertion and afterwards it works to call teh repo's rest endpoint.
Error msg from log
Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Couldn't find PersistentEntity for type class io.vavr.collection.List$Cons!; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Couldn't find PersistentEntity for type class io.vavr.collection.List$Cons! (through reference chain: org.springframework.hateoas.PagedResources["_embedded"]->java.util.Collections$UnmodifiableMap["myEntities"]->java.util.ArrayList[0]->org.springframework.data.rest.webmvc.json.PersistentEntityJackson2Module$PersistentEntityResourceSerializer$1["content"]->de.spring.demo.entity.MyEntity["myList"])
It sounds like some mappers have to be injected which are automatically injected after inserting a new entry (or some lazy loading maybe...)
A sample can be found here: https://github.com/renne-b/spring-rest-demo
It would be great to get a hint what's missing.
some details:
latest spring boot milestone: 2.0.0.M3
I registered VavrModule at ObjectMapper
#EnableMongoRepositories(basePackages = "for my path to classes")

Answer 1

I update your project with
Spring boot 2.0.0.RELEASE
EmbeddedMongo de.flapdoodle.embed:de.flapdoodle.embed.mongo:2.0.3 / 3.2.2:Windows:B64
Fix JSON mapping
And after that request curl http://localhost:8080/myEntities executed without problems:
{
"_embedded" : {
"myEntities" : [ ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/myEntities{?page,size,sort}",
"templated" : true
},
"profile" : {
"href" : "http://localhost:8080/profile/myEntities"
}
},
"page" : {
"size" : 20,
"totalElements" : 0,
"totalPages" : 0,
"number" : 0
}
}
After add 2 entities:
{
"_embedded" : {
"myEntities" : [ {
"foo" : "bar1521033137701",
"myList" : {
"content" : [ "bla" ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/myEntities/5aa91fb1bec7c7169c9b5943"
},
"myEntity" : {
"href" : "http://localhost:8080/myEntities/5aa91fb1bec7c7169c9b5943"
}
}
}, {
"foo" : "bar1521033145175",
"myList" : {
"content" : [ "bla" ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/myEntities/5aa91fb9bec7c7169c9b5944"
},
"myEntity" : {
"href" : "http://localhost:8080/myEntities/5aa91fb9bec7c7169c9b5944"
}
}
} ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/myEntities{?page,size,sort}",
"templated" : true
},
"profile" : {
"href" : "http://localhost:8080/profile/myEntities"
}
},
"page" : {
"size" : 20,
"totalElements" : 2,
"totalPages" : 1,
"number" : 0
}
}