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How to deserialize Json content with unknown property when using Jackson

When using Jackson to deserialize a Json string, if the Java object does’t include all the fields in the Json, Jackson will complain about unknown properties. In this post I will show how to ignore the properties if it is not defined in our Java object.

Suppose we have the following Json string:

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{
    "name": "name1", 
    "studentId": "12345",
    "major": "computer science"
}

And the Java object:

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class Student {
    String name;
    int studentId;

    // getters and setters
}

When we map the Json to the Java object, will see the following exception:

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com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: 
Unrecognized field "major" (class com.experiment.jackson.JacksonDeserialize$Student), 
not marked as ignorable (2 known properties: "name", "studentId"])

There are 2 ways to deal with this problem:

  1. Configure the ObjectMapper to ignore unknown properties

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    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

  2. Mark the Java object to ignore unknown field. This way we only specify to ignore unknown properties when deserialize this particular class.

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    @JsonIgnoreProperties (ignoreUnknown = true)
    class Student {
        String name;
        int studentId;
        
        // getters and setters
    }