Convert JsonNode into POJO

Question

This may seem a little unusual  but I am looking for an efficient way to transform map a JsonNode into a POJO   I store some of my Model s information in json files and I have to support a couple of version of my model   What I do is load the json file in memory in a JsonNode  apply a couple of versioning strategies  to make it match the latest version of my Model       ObjectMapper mapper   new ObjectMapper        BufferedReader fileReader   new BufferedReader new FileReader projPath         JsonNode rootNode   mapper readTree fileReader          Upgrade our file in memory     applyVersioningStrategy rootNode        ProjectModel project   mapJsonNodeToProject rootNode     Unless there s a faster way to do it  I will probably end up simply manually applying the JsonNodes to my Model

User · Accepted Answer

In Jackson 2 4  you can convert as follows   MyClass newJsonNode   jsonObjectMapper treeToValue someJsonNode  MyClass class     where jsonObjectMapper is a Jackson ObjectMapper     In older versions of Jackson  it would be  MyClass newJsonNode   jsonObjectMapper readValue someJsonNode  MyClass class

User · Answer

This should do the trick   mapper readValue fileReader  MyClass class     I say should because I m using that with a String  not a BufferedReader but it should still work   Here s my code   String inputString      I grab my string here MySessionClass sessionObject  try       ObjectMapper objectMapper   new ObjectMapper        sessionObject   objectMapper readValue inputString  MySessionClass class     Here s the official documentation for that call  http   jackson codehaus org 1 7 9 javadoc org codehaus jackson map ObjectMapper html readValue java lang String  java lang Class   You can also define a custom deserializer when you instantiate the ObjectMapper  http   wiki fasterxml com JacksonHowToCustomDeserializers  Edit  I just remembered something else  If your object coming in has more properties than the POJO has and you just want to ignore the extras you ll want to set this       objectMapper configure DeserializationConfig Feature FAIL ON UNKNOWN PROPERTIES  false     Or you ll get an error that it can t find the property to set into

User · Answer

String jsonInput        hi      Assume this is the JSON       com fasterxml jackson databind ObjectMapper mapper       new com fasterxml jackson databind ObjectMapper    MyClass myObject   objectMapper readValue jsonInput  MyClass class     If your JSON input in has more properties than your POJO has and you just want to ignore the extras in Jackson 2 4  you can configure your ObjectMapper as follows  This syntax is different from older Jackson versions   If you use the wrong syntax  it will silently do nothing    mapper disable com fasterxml jackson databind DeserializationFeature FAIL ON UNK  NOWN PROPERTIES

User · Answer

If you re using org codehaus jackson  this has been possible since 1 6  You can convert a JsonNode to a POJO with ObjectMapper readValue  http   jackson codehaus org 1 9 4 javadoc org codehaus jackson map ObjectMapper html readValue org codehaus jackson JsonNode  java lang Class        ObjectMapper mapper   new ObjectMapper        JsonParser jsonParser   mapper getJsonFactory   createJsonParser     foo     bar           JsonNode tree   jsonParser readValueAsTree           Do stuff to the tree     mapper readValue tree  Foo class

[java] Convert JsonNode into POJO

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