How Can Jackson Ignore Unknown Fields During JSON Deserialization?

Overcoming JSON Field Changes in Jackson

Managing JSON data in Android applications can be challenging, especially when schema changes are introduced. The Jackson library is widely used for JSON mapping, but it can be sensitive to the addition of new fields in JSON objects.

Question:

How can Jackson be configured to ignore new fields added to JSON objects during the deserialization process?

Answer:

Jackson provides a versatile solution to this problem: the @JsonIgnoreProperties annotation can be applied at the class level to instruct the library to ignore unrecognized properties when deserializing JSON data.

To ignore all new fields, add the following annotation to the POJO class:

@JsonIgnoreProperties(ignoreUnknown = true)
public class Foo {
    ...
}

Depending on the Jackson version used, the import statement will vary:

• Current version: com.fasterxml.jackson.annotation.JsonIgnoreProperties
• Older versions: org.codehaus.jackson.annotate.JsonIgnoreProperties

With this annotation in place, Jackson will disregard any fields in the JSON object that are not defined in the POJO class, allowing for seamless compatibility even when the JSON schema changes.

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