如何使用Jackson将“名称”“值”对的JSON数组反序列化为Pojo

Question

I want to deserialize the following JSON object:

{
  "id":"001",
  "module_name":"Users",
  "name_value_list":
    {
      "user_name": {"name":"user_name", "value":"admin"},
      "full_name": {"name":"full_name", "value":"Lluís Pi"},
      "city": {"name":"full_name", "value":"Barcelona"},
      "postal_code": {"name":"postal_code", "value":"08017"},
      ...
    }
}

into some Java object like this:

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility = JsonAutoDetect.Visibility.NONE)
public class UserEntry
{
  private String id;
  private String moduleName;
  private Person nameValueList;

  public String getId()
  {
    return id;
  }

  public String getModuleName()
  {
    return moduleName;
  }

  public Person getPerson()
  {
    return nameValueList;
  }
}

where Person is the following class:

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility = JsonAutoDetect.Visibility.NONE)
class Person 
{
  private String userName;
  private String fullName;
  private String city;
  private String postalCode;
}

using Jackson but I get a deserialization error.

If I change the type of field nameValueList to a Map all the deserialization process goes with no problem and I get a map where the key is the "name" value and the value is the "value" value.

So my question is: is there any simple, or no so simple, way to deserialize this kind of JSON object to a Java Pojo with properties prop_1 , prop_2 , prop_3 and prop_4 ?

{
  "name_value_list":
    {
      "prop_1": {"name":"prop_1", "value":"value_1"},
      "prop_2": {"name":"prop_2", "value":"value_2"},
      "prop_3": {"name":"prop_3", "value":"value_3"},
      "prop_4": {"name":"prop_4", "value":"value_4"},
      ...
    }
}

Answer 1

Not very simple and not very clean. However you can do it by implementing a any setter field for the JSON attributes in the Person class which don't match any attribute on your UserEntry POJO.

@JsonAnySetter
public void putUserField(String userKey, Map<String, String> userValue) 
  throws NoSuchFieldException {
    String actualFieldName = getActualFieldName(userKey);
    Field field = this.getClass().getDeclaredField(actualFieldName);
    field.setAccessible(true);
    ReflectionUtils.setField(field, this, userValue.get("value"));
}

private String getActualFieldName(String userKey) {
    return CaseFormat.LOWER_UNDERSCORE.to(CaseFormat.LOWER_CAMEL, userKey);
}

In addition to that, I had to change the Jackson attributes for the Person class to

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.PUBLIC_ONLY, 
  getterVisibility = JsonAutoDetect.Visibility.NONE)

for it to work for attributes like "city" which don't need any name transformation because jackson tries to directly set the field which fails.