Here's an example of using @JsonSetter annotations as a "preprocessor"-like way to move clients using old API while still being able to update Orca's internal model.

JsonSetterSpec.groovy

/*
 * Copyright 2016 Google, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License")
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.netflix.spinnaker.orca.clouddriver

import com.fasterxml.jackson.annotation.JsonSetter
import com.fasterxml.jackson.databind.ObjectMapper
import groovy.transform.Canonical
import spock.lang.Specification

class MixinTest extends Specification {

  def "should pass"() {
    given:
      ObjectMapper mapper = new ObjectMapper()

    when:
      Pojo result = mapper.readValue("{\"region\": \"foo\"}", Pojo)

    then:
      result
      result.regions == ["foo"]

    when:
      result = mapper.readValue("{\"regions\": [\"foo\", \"bar\"]}", Pojo)

    then:
      result
      result.regions == ["foo", "bar"]

    when:
      result = mapper.readValue("{\"someOlderApiValue\": [\"foo\", \"bar\"]}", Pojo)

    then:
      result
      result.regions == ["foo", "bar"]
  }

  @Canonical
  static class Pojo {
    // Most up-to-date model
    List<String> regions

    @JsonSetter("region")
    String fromRegion(String r) {
      regions = [r]
    }

    @JsonSetter("someOlderApiValue")
    String fromSomeOlderApiValue(List l) {
      regions = l
    }
  }
}