如何使用rest模板spring boot映射此Json

Question

我是REST API的新手，我必须映射一个endpoint来返回这个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": []
                }
            }
        },

我有我的控制器与此调用：

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

我的服务实现：

@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);
}

现在我有点糊涂了。我创建了OfferMapper来接收来自这个JSON的所有属性，但有些属性将为空。我也不知道创建子对象（OfferRequest请求、OfferResponse响应）是否是映射它的正确方法。

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

以下是OfferResponse请求和响应：

@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;
}

当我打电话给邮递员时，我得到了这样的回应：

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

}

这个调用返回了一些值，但是我不明白为什么我会得到这些空值，也不明白我要如何在Java中实现这个部分，因为它不像一个列表结构，JSON没有[]只提供{}:

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

Answer 1

尝试@SerializedName（“Field_name”）作为开头的字段按大写字母（目标，格式...）

@SerializedName("Target")
private String target;

我认为在这些变化之后，你可以得到价值。

Answer 2

在您的API响应中，您会得到这样的结果(我只使用了一个片段，但是您可以将这个想法扩展到所有其他字段):

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

但是，在您的POJO中，您有以下内容：

public class OfferRequest {

  private String target;
  private String format;

您必须知道，Jackson在序列化/反序列化时将使用反射，除非另有规定。这意味着，如果您声明字段名为＜code＞target，它将期望Json包含＜code＞target。

请注意，让Jackson使用反射而不是使用Jackson的注释是一种糟糕的做法，因为您严格地将代码链接到它们表示的Json（不应该是这种情况）。

为了使您的代码可靠，我建议如下：

首先，使用@JsonProperty注释显式命名字段：

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

其次，声明字段＜code＞final＜/code＞（它们无论如何都不应该更改）：

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

以上将强制您在构造函数中初始化它们。因此，您可以为您的类创建一个构造函数，您将使用@JsonConstructor对其进行注释，并指导Jackson正确构建您的类：

@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");
}

像这样，您明确地告诉Jackson，您希望字段Target在Json中，如果不是，您将有一个解析异常。

另外，对象。requireNonNull（）是检查字段不应为null（因为如果Json包含“Target”：null，Jackson将看到该字段，并无论如何让它通过）。