How can you avoid processing new fields when converting JSON into an existing Java object?

To ignore new (unknown) fields when deserializing JSON into an existing Java object, you can use the settings of the library performing the conversion. For example, when using Jackson:

• Add the annotation @JsonIgnoreProperties(ignoreUnknown = true) to the class to ignore fields that are missing in the class.

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class MyClass {
    private String knownField;
    // getters and setters
}

• Or configure the ObjectMapper:

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

Thus, new fields in JSON will not cause errors and will not be processed, preserving the existing object structure.