I would like serialize an object such that one of the fields will be named differently based on the type of the field. For example:
public class Response {
private Status status;
private String error;
private Object data;
[ getters, setters ]
}
Here, I would like the field data to be serialized to something like data.getClass.getName() instead of always having a field called data which contains a different type depending on the situation.
我怎样才能用杰克逊达到这样的目的呢？
Using a custom JsonSerializer.
public class Response {
private String status;
private String error;
@JsonProperty("p")
@JsonSerialize(using = CustomSerializer.class)
private Object data;
// ...
}
public class CustomSerializer extends JsonSerializer<Object> {
public void serialize(Object value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
jgen.writeStartObject();
jgen.writeObjectField(value.getClass().getName(), value);
jgen.writeEndObject();
}
}
And then, suppose you want to serialize the following two objects:
public static void main(String... args) throws Exception {
ObjectMapper mapper = new ObjectMapper();
Response r1 = new Response("Error", "Some error", 20);
System.out.println(mapper.writeValueAsString(r1));
Response r2 = new Response("Error", "Some error", "some string");
System.out.println(mapper.writeValueAsString(r2));
}
第一个将打印:
{"status":"Error","error":"Some error","p":{"java.lang.Integer":20}}
第二个是:
{"status":"Error","error":"Some error","p":{"java.lang.String":"some string"}}
I have used the name p for the wrapper object since it will merely serve as a placeholder. If you want to remove it, you'd have to write a custom serializer for the entire class, i.e., a JsonSerializer<Response>.