What are the steps to reproduce your problem?

A sample application is attached for quick reference.

Steps followed

• Installed Camunda spring boot starter 7.15.0-ee
• Created Java Delegate with the name SomeDelegate which sets an object variable in Java API.
• Deployed sample BPMN recreate_error.bpmn which calls this Java delegate via process application
• Started the server
• Go to tasklist, and start the process instance
• Now in Tasklist, go to the User Task, claim the task and "Load the variable" in generic User Task form
• Submit the generic user task form
• An exception is thrown as shown in the screenshot below
  
  Stack trace shows following as cause:

  Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `test.camunda.DeliveryInformation` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('{"id":"f8d791db-924e-4def-a63a-da069298b26d","packages":[{"id":"id1","storageAreaId":"areaa1","storageId":"storage1","article":null}],"carrier":"carrier1"}')
   at [Source: UNKNOWN; line: -1, column: -1]
  	at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1455) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1081) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.deser.ValueInstantiator._createFromStringFallbacks(ValueInstantiator.java:371) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromString(StdValueInstantiator.java:323) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1408) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:176) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.ObjectMapper._readValue(ObjectMapper.java:4497) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2799) ~[jackson-databind-2.11.3.jar:2.11.3]
  	at org.camunda.spin.impl.json.jackson.format.JacksonJsonDataFormatMapper.mapInternalToJava(JacksonJsonDataFormatMapper.java:98) ~[camunda-spin-dataformat-json-jackson-1.10.1.jar:1.10.1]
  	... 248 common frames omitted
  
  

What is the problem?
Deserialization fails for object

What would be the expected behavior:
No error in saving serialized object

Hints (optional):

• This always happens when you submit an object variable from the task form (you can also create a new one and look up the variable in the history, it cannot be deserialized as well).
• The quotation marks used in the serialized String are not handled correctly. This works all fine in the "Add Variable to Process Instance" dialog in Cockpit