POST http://localhost:8081/quiz/v0/quiz 400 ()

"{"timestamp":1487612926565,"status":400,"error":"Bad Request","exception":"org.springframework.http.converter.HttpMessageNotReadableException","message":"Could not read document: Can not construct instance of de.thkoeln.archilab.quizeditor.entities.Question: abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information\n at [Source: java.io.PushbackInputStream@1c6c14c; line: 1, column: 346] (through reference chain: de.thkoeln.archilab.quizeditor.entities.Quiz[\"questions\"]->java.util.HashSet[0]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of de.thkoeln.archilab.quizeditor.entities.Question: abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information\n at [Source: java.io.PushbackInputStream@1c6c14c; line: 1, column: 346] (through reference chain: de.thkoeln.archilab.quizeditor.entities.Quiz[\"questions\"]->java.util.HashSet[0])","path":"/quiz/v0/quiz"}"