Here is an example of using the JsonIgnore annotation from the Apache Commons IO library to ignore a field when serializing an object to JSON:

import org.apache.commons.io.output.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties({"fieldToIgnore"})
public class MyClass {
    private String fieldToIgnore;
    private String fieldToKeep;

    public MyClass(String fieldToIgnore, String fieldToKeep) {
        this.fieldToIgnore = fieldToIgnore;
        this.fieldToKeep = fieldToKeep;
    }
    
    public String getFieldToKeep() {
        return fieldToKeep;
    }
    
    @JsonIgnore
    public String getFieldToIgnore() {
        return fieldToIgnore;
    }
}

In this example, the fieldToIgnore is annotated with @JsonIgnore which will be ignored during serialization. Also, it is annotated with @JsonIgnoreProperties({"fieldToIgnore"}) at class level to ignore the field.

Make sure that you are using jackson as serializer.