2017-02-20 23:50:16.204  WARN 3888 --- [nio-8081-exec-6] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of de.thkoeln.archilab.quizeditor.entities.Quiz out of START_ARRAY token
 at [Source: java.io.PushbackInputStream@eb18d7; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of de.thkoeln.archilab.quizeditor.entities.Quiz out of START_ARRAY token
 at [Source: java.io.PushbackInputStream@eb18d7; line: 1, column: 1]
2017-02-20 23:50:16.204  WARN 3888 --- [nio-8081-exec-6] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved exception caused by Handler execution: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of de.thkoeln.archilab.quizeditor.entities.Quiz out of START_ARRAY token
 at [Source: java.io.PushbackInputStream@eb18d7; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of de.thkoeln.archilab.quizeditor.entities.Quiz out of START_ARRAY token
 at [Source: java.io.PushbackInputStream@eb18d7; line: 1, column: 1]
2017-02-20 23:50:16.207 ERROR 3888 --- [nio-8081-exec-5] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause