如何从json响应中获取特定对象

Question

I'm receiving a response from one third party service which looks like this:

{
    "field1": "string",
    "field2": "string",
    "objectList": [
        {
            "object1": {
                "field11": "string",
                "field12": "string",
                "field13": "string",
                "field14": "string",
            },
            "object2": {
                "field21": "string",
                "field22": "string",
                "field23": "string",
            },
            "object3": {
                "field31": "string",
                "field32": "string",
                "field33": "string",
                "field34": "string",
                "field35": "string",
            }
        }
    ]
}

object1, object2 and object3 are not the same type, and I just want to get the object2 from the response.

I have tried this approach:

ResponseEntity<ResponseClass> response = restTemplate.exchange( uri, HttpMethod.POST, entity, ResponseClass.class );

Where ResponseClass looks like this:

@JsonIgnoreProperties(ignoreUnknown = true)
@Data
public class ResponseClass implements Serializable {

    private static final long serialVersionUID = -4355652702566088304L;

    @JsonProperty("field1")
    private String field1;
    @JsonProperty("field2")
    private String field2;
    @JsonProperty("objectList")
    private List objectList;

And I'm getting the full objectList, so I can extract it as key value pairs like objectList.get(0).get("object2") or something like that. But I'm unsure if there is a better solution.

Can anyone please provide some guidance on how to improve this or how to get just the object I want?

Answer 1

There are two ways to look at it.

Extensibility and pure object-oriented way:

You need to map the whole response object properly at your side rather than having an ambiguous List. An array should always have objects of same type. In your example too basically you have a list of wrapper object which hold object1, object2, and object3.

So, basically you should do something like this :

@JsonIgnoreProperties(ignoreUnknown = true)
@Data
public class ResponseClass implements Serializable {

    private static final long serialVersionUID = -4355652702566088304L;

    @JsonProperty("field1")
    private String field1;
    @JsonProperty("field2")
    private String field2;
    @JsonProperty("objectList")
    private List<IntendedObject> objectList;
 }


@JsonIgnoreProperties(ignoreUnknown = true)
@Data
public class IntendedObject {
    @JsonProperty("object2")
    private Object2 object2;
 }

The other way would be to have the response in a JsonNode and then do getProperty() over it if you don't want to map it over to a custom object.

Answer 2

objectList[0].object2

0 给你列表中的第一项然后 object2 访问字典的值