Error while Parsing json into scala case class
In my spring(mvc) web application, I am using org.codehaus.jackson.map.ObjectMapper in my scala code to map my json to scala objects using case classes. My Json String is an array of json objects objects. so I am using:
val user = mapper.readValue(myJson, classOf[List[MyClass]])
This line throws an error:
Exception in thread "main" org.codehaus.jackson.map.JsonMappingException: Can not construct instance of scala.collection.immutable.List, problem: abstract types can only be instantiated with additional type inform
Am I using it right or is there any other way?
The problem is the Java type erasure. classOf[List[MyClass]] at runtime is the same as classOf[List[_]] . That is why Jackson cannot know, which types of the elements to create.
Luckily Jackson does support parsing with the JavaType , which describes the types themselves.
Here a simple sample in Java:
JavaType type = mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class);
mapper.readValue(myJson, type);