如何将此 Json 与 rest 模板 spring boot 映射

Question

I'm kind of new to REST API and I have to map an endpoint that returns me this JSON:

{
"request": {
    "Target": "Affiliate_Offer",
    "Format": "json",
    "Service": "HasOffers",
    "Version": "2",
    "api_key": "3225235c5633454cf60d35838cf8466f8fcf184b1360d",
    "Method": "findAll",
    "contain": [
        "Country"
    ]
},
"response": {
    "status": 1,
    "httpStatus": 200,
    "data": {
        "18292": {
            "Offer": {
                "id": "18292",
                "name": "247 Profit Formula",
                "description": "<b>Description:</b> Register for a chance to earn $500 or more per day from home!<br><br>\r\n\r\n<b>Requirement:</b> First Page Submit<br><br>\r\n\r\n<b>Country(ies):</b> US<br><br>\r\n\r\n<b>Media:</b> Blog, Display, Newsletter, Social Media, Text Links<br><br>\r\n\r\n<b>Restrictions:</b> No Incentives; no Email<br><br>\r\n\r\n<b>Other:</b> None.<br><br>\r\n",
                "require_approval": "0",
                "require_terms_and_conditions": 0,
                "terms_and_conditions": null,
                "preview_url": "https://www.247profitsecret.com/formula?",
                "currency": null,
                "default_payout": "0.90000",
                "protocol": "server",
                "status": "active",
                "expiration_date": "2039-01-06 04:59:59",
                "payout_type": "cpa_flat",
                "percent_payout": null,
                "featured": null,
                "conversion_cap": "0",
                "monthly_conversion_cap": "0",
                "payout_cap": "0.00",
                "monthly_payout_cap": "0.00",
                "allow_multiple_conversions": "0",
                "allow_website_links": "0",
                "allow_direct_links": "0",
                "show_custom_variables": "0",
                "session_hours": "24",
                "show_mail_list": "0",
                "dne_list_id": "0",
                "email_instructions": "0",
                "email_instructions_from": "Your List Name",
                "email_instructions_subject": "Survey Takers Needed\r\nFortune 500 Companies Need You!\r\nEarn $45 Per Online Survey\r\nSimple Survey Jobs",
                "enforce_secure_tracking_link": "1",
                "has_goals_enabled": "0",
                "default_goal_name": "",
                "modified": 1634138487,
                "use_target_rules": "0",
                "use_payout_groups": "0",
                "link_platform": null,
                "is_expired": "0",
                "dne_download_url": null,
                "dne_unsubscribe_url": null,
                "dne_third_party_list": false,
                "approval_status": "approved"
            },
            "Country": {
                "US": {
                    "id": "840",
                    "code": "US",
                    "name": "United States",
                    "regions": []
                }
            }
        },
        "17823": {
            "Offer": {
                "id": "17823",
                "name": "American Career Guide",
                "description": "<b>Description:</b> American Career Guide is your free guide to help you search jobs in your city!<br><br>\r\n\r\n<b>Requirement:</b> Email Submit<br><br>\r\n\r\n<b>Country(ies):</b> US<br><br>\r\n\r\n<b>Media:</b> Display, Email, Newsletter, Search, Text Link<br><br>\r\n\r\n<b>Restrictions:</b> 18+; no Incentives, no Social Media<br><br>\r\n\r\n<b>Other:</b> Contact Affiliate Manager for Suppression list.   <br><br>\r\n",
                "require_approval": "1",
                "require_terms_and_conditions": 0,
                "terms_and_conditions": null,
                "preview_url": "https://jobs.theamericancareerguide.com/api/offer",
                "currency": null,
                "default_payout": "2.40000",
                "protocol": "server",
                "status": "active",
                "expiration_date": "2030-01-08 04:59:59",
                "payout_type": "cpa_flat",
                "percent_payout": null,
                "featured": null,
                "conversion_cap": "200",
                "monthly_conversion_cap": "0",
                "payout_cap": "0.00",
                "monthly_payout_cap": "0.00",
                "allow_multiple_conversions": "0",
                "allow_website_links": "0",
                "allow_direct_links": "0",
                "show_custom_variables": "1",
                "session_hours": "24",
                "show_mail_list": "0",
                "dne_list_id": "0",
                "email_instructions": "1",
                "email_instructions_from": "AmericanCareerGuide\r\nAmerican_Career_Guide\r\nTheAmericanCareerGuide\r\nJobsAvailable",
                "email_instructions_subject": "Job Offers Are Waiting For You\r\nJobs Available - Positions Paying Up to $35/Hour\r\nHelp Wanted - Jobs Available in Your Area!\r\nHelp Wanted in Your Area - Pick Your New Job Today!\r\nLooking for a New Career?  Jobs Available in Your Area!\r\nThere Are Jobs Paying $25/Hour+ in Your City!  Search Now!",
                "enforce_secure_tracking_link": "1",
                "has_goals_enabled": "0",
                "default_goal_name": "",
                "modified": 1647550322,
                "use_target_rules": "0",
                "use_payout_groups": "0",
                "link_platform": null,
                "is_expired": "0",
                "dne_download_url": null,
                "dne_unsubscribe_url": null,
                "dne_third_party_list": false,
                "approval_status": null
            },
            "Country": {
                "US": {
                    "id": "840",
                    "code": "US",
                    "name": "United States",
                    "regions": []
                }
            }
        },

I have my controller with this call:

 @GetMapping("/find-all-offers-api")
public ResponseEntity<OfferMapper> findAllOffersApi() {
    log.info("Find All Offers From Api - Controller Call");
   return service.findAllOffersApi();
}

My service implementation:

@Override
public ResponseEntity<OfferMapper> findAllOffersApi() {
    log.info("Find All Offers From Api - Service Call");
    HttpHeaders headers = new HttpHeaders();
    headers.setAccept(List.of(MediaType.APPLICATION_JSON));
    HttpEntity<String> entity = new HttpEntity<>("parameters", headers);
    return restTemplate.exchange(GET_ALL_OFFERS_API, HttpMethod.GET, entity, OfferMapper.class);
}

Now I'm getting a little bit confused. I created the OfferMapper to receive all the attributes from this JSON but some properties are coming null also I don't know if creating sub-objects (OfferRequest request, OfferResponse response) is the correct way to map it.

@Data
@AllArgsConstructor
@NoArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class OfferMapper {
  OfferRequest request;
  OfferResponse response;
}

Here is the OfferResponse request and response:

@Data
@NoArgsConstructor
@AllArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class OfferRequest {

  private String target;
  private String format;
  private String service;
  private String version;
  private String api_key;
  private String method;
  private List<String> contains;

}

@Data
@NoArgsConstructor
@AllArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class OfferResponse {
   private int status;
   private int httpStatus;
   private OfferData data;
}

When I call with postman I get this response:

{
"request": {
    "target": null,
    "format": null,
    "service": null,
    "version": null,
    "api_key": "3225235c5633454cf60d35838cf8466f8fcf184b1360d",
    "method": null,
    "contains": null
},
"response": {
    "status": 1,
    "httpStatus": 200,
    "data": {
        "offer": null
    }
}

}

The call return some values but I don't understand why Im getting those nulls values and also how I'm gonna make this part in Java because its not like a list structure the JSON does not have [] for the offers only {}:

"data": {
    "18292": {
        "Offer": {
            "id": "18292",
            "name": "247 Profit Formula",

Answer 1

In your API response, you're getting this (I only use one fragment but you can extend the idea to all the other fields):

{
    "request": {
        "Target": "Affiliate_Offer",
        "Format": "json",

However, in your POJO, you have this:

public class OfferRequest {

  private String target;
  private String format;

You must know that Jackson, when serializing/deserializing, will use reflection unless differently specified. That means, if you're declaring the field to be named target , it will expect the Json to contain target and not Target .

Note that letting Jackson use reflection instead of using Jackson's annotations is a bad practice, because you strictly link your code to the Json they represent (which should not be the case).

In order to make your code solid, these are the things I suggest:

First, explicitly name your fields using the @JsonProperty annotation:

@JsonProperty("Target") //<-- I'm saying the serialized name of this property is Target with capital T
private String target;

Second, declare the fields final (they are not supposed to change anyway):

private final String target; //<-- field must be initialized and can't change its value anymore

The above will force you to initialize them in the constructor. So you can create a constructor for your class, that you will annotate with @JsonConstructor and will guide Jackson to build your class correctly:

@JsonCreator
public OfferRequest(@JsonProperty(value = "Target", required = true) String target) { //<-- you require the field Target to be present, else you stop the Json deserialization with an error
    this.target = requireNonNull(target, "target should not be null");
}

Like this, you're explicitly telling to Jackson that you expect a field Target to be in the Json and if it's not, you'll have a parse exception.

Also, the Objects.requireNonNull() is your way to check that the field should not be null (because if the Json contains "Target": null , Jackson will see the field and will let it pass anyway).

Answer 2

Try @SerializedName("Field_name") for field that start's By uppercase(Target, Format...)

@SerializedName("Target")
private String target;

I think after this changes 'u can get values.