Jackson 2 to 3 migration companion code

Three Maven modules - jackson2-before (2.22.1), jackson3-after (3.2.1) and a coexistence module with BOTH majors on one classpath - so every claim in the two migration guides is executed rather than asserted. Paired class names make the before/after outputs directly diffable via run-all.sh. Confirms the guides on wire-format equivalence (10-case suite, zero mismatches), classpath coexistence and the collapse of four artifacts into one. Corrects nine points, including that enableDefaultTyping() is still present in Jackson 2.22.1 rather than removed in 2.16, and that the published "after" mapper snippet does not compile.
2026-08-04 23:29:27 +05:30
commit f0a7053fc9
43 changed files with 1665 additions and 0 deletions
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+output          : {"id":1,"travelDate":"2026-09-15","seatPreference":"aisle"}
+forked indented : { "id" : 1, "travelDate" : "2026-09-15", "seatPreference" : "aisle" }
+original intact : false
+set*() mutators : 0   <- mutation is impossible, not merely discouraged
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+JacksonException extends RuntimeException : true
+JacksonException extends IOException      : false
+ESCAPED catch (IOException)   : StreamReadException
+caught by catch (Jackson...)  : StreamReadException
+writeValueAsString declares   : [class tools.jackson.core.JacksonException]  <- nothing checked
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+serialised   : {"amount":19.99,"currency":"USD"}
+deserialised : Money[amount=20.0, currencyCode=USD]
+base classes : tools.jackson.databind.ValueSerializer / tools.jackson.databind.ValueDeserializer
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+no modules      : {"id":1,"departure":"2026-09-15","seat":"12A"}
+round-trip      : TravelPlan[id=1, departure=2026-09-15, seat=Optional[12A]]
+dates           : {"d":"2026-09-15"}
+empty Optional  : {"id":2,"departure":"2026-09-16","seat":null}
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+enableDefaultTyping    on Jackson 3 ObjectMapper : false
+activateDefaultTyping  on Jackson 3 ObjectMapper : false
+activateDefaultTyping  on JsonMapper.Builder    : true
+
+written : {"@class":"com.ankurm.migration.after.S05DefaultTyping$Envelope","body":{"@class":"com.ankurm.migration.after.S05DefaultTyping$SafePayload","note":"ok"}}
+read    : SafePayload[ok]
+rogue   : rejected with InvalidTypeIdException
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+FAIL_ON_TRAILING_TOKENS      : true
+FAIL_ON_UNKNOWN_PROPERTIES   : false
+ALLOW_FINAL_FIELDS_AS_MUTATORS: false
+DEFAULT_VIEW_INCLUSION       : false
+AUTO_DETECT_CREATORS exists  : false
+
+concatenated JSON  -> rejected: MismatchedInputException
+trailing garbage   -> rejected: StreamReadException
+unknown property   -> accepted: OrderDto[orderId=1]
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+output          : {"id":1,"travelDate":"2026-09-15","seatPreference":"aisle"}
+after mutation  : { "id" : 1, "travelDate" : "2026-09-15", "seatPreference" : "aisle" }
+mutation stuck  : true
+set*() mutators : 40
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+JsonProcessingException extends IOException : true
+caught by catch (IOException) : JsonParseException
+writeValueAsString declares    : [class com.fasterxml.jackson.core.JsonProcessingException]
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+serialised   : {"amount":19.99,"currency":"USD"}
+deserialised : Money[amount=20.0, currencyCode=USD]
+base classes : com.fasterxml.jackson.databind.JsonSerializer / com.fasterxml.jackson.databind.JsonDeserializer
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+with modules    : {"id":1,"departure":"2026-09-15","seat":"12A"}
+round-trip      : TravelPlan[id=1, departure=2026-09-15, seat=Optional[12A]]
+bare mapper     : FAILS -> InvalidDefinitionException
+bare, dates only: FAILS -> InvalidDefinitionException
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+enableDefaultTyping on Jackson 2.22 ObjectMapper : true
+written : {"@class":"com.ankurm.migration.before.S05DefaultTyping$Envelope","body":{"@class":"com.ankurm.migration.before.S05DefaultTyping$SafePayload","note":"ok"}}
+read    : SafePayload[ok]
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+FAIL_ON_TRAILING_TOKENS      : false
+FAIL_ON_UNKNOWN_PROPERTIES   : true
+ALLOW_FINAL_FIELDS_AS_MUTATORS: true
+DEFAULT_VIEW_INCLUSION       : true
+AUTO_DETECT_CREATORS exists  : true
+
+concatenated JSON  -> accepted: OrderDto[orderId=1]
+trailing garbage   -> accepted: OrderDto[orderId=1]
+unknown property   -> rejected: UnrecognizedPropertyException
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+jackson 2 class : com.fasterxml.jackson.databind.ObjectMapper
+jackson 3 class : tools.jackson.databind.json.JsonMapper
+
+jackson 2 output: {"booking_id":1,"travel_date":"2026-09-15"}
+jackson 3 output: {"booking_id":1,"travel_date":"2026-09-15"}
+wire-compatible : true
+
+3 reads 2's JSON: Booking[id=1, travelDate=2026-09-15]
+2 reads 3's JSON: Booking[id=1, travelDate=2026-09-15]
+
+annotation from : jackson-annotations-2.22.jar
+  <- one jackson-annotations jar, used by both majors
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+plain record       identical
+nested list        identical
+map                identical
+java.time          identical
+Optional present   identical
+Optional empty     identical
+NON_NULL           identical
+@JsonProperty      identical
+@JsonFormat        identical
+nulls and empties  identical
+
+cases     : 10
+mismatches: 0
+Wire format is identical across both majors for these cases.