如何在 Spring Boot 中使用 RestTemplate 从来自外部 REST API 的 JSON 响应中提取数据？

Question

我正在使用 RestTemplate 开发 spring 引导应用程序以使用外部 API。

下面是我为从外部 API 获得响应而编写的服务 class：

public CustomOlapReports getReportListByClientId(String clientId) {
        ResponseEntity<CustomOlapReports> responseEntity = null;
        CustomOlapReports jsonResponse = null;
        try {
            final String uri = "https://chapi.cloudhealthtech.com/olap_reports/custom?client_api_id="+clientId;
            RestTemplate restTemplate = new RestTemplate();
            HttpHeaders header = new HttpHeaders();
            header.set(HttpHeaders.AUTHORIZATION, "Bearer "+apiKey);
            header.set(HttpHeaders.ACCEPT, "application/json");
            
            HttpEntity<String> requestEntity = new HttpEntity<String>("body",header);
            responseEntity = restTemplate.exchange(uri, HttpMethod.GET, requestEntity, CustomOlapReports.class);
            
            jsonResponse =  responseEntity.getBody();   
        } catch (Exception e) {
            e.printStackTrace();
        }
    return jsonResponse;
}

以下是我使用 exchange() 方法得到的响应：

{
    "responseMessage": "SUCCESS",
    "status": "OK",
    "statusCode": 1,
    "response": {
        "links": {
            "RCDSO - Production Environment Cost": {
                "href": "href 1"
            },
            "RCDSO - Development & UAT Environment Cost": {
                "href": "href 2"
            },
            "RCDSO - Total Cost for Prod - Compugen Managed": {
                "href": "href 3"
            },
            "RCDSO - Virtual Machine Cost": {
                "href": "href 4"
            },
            "RCDSO - Azure File Storage Cost": {
                "href": "href 5"
            },
            "RCDSO - Azure Backup and Site Recovery": {
                "href": "href 6"
            },
            "RCDSO - Azure App Services Cost": {
                "href": "href 7"
            }
        }
    }
}

/********************** CustomOlapReports.java *************************/

@Getter
@Setter
public class CustomOlapReports {
    
     @JsonProperty("links") 
     private Links links;
}
/********************** Links.java *************************/
@Setter
@Getter
public class Links {
    @JsonProperty("RCDSO - Production Environment Cost")
    private RCDSOProductionEnvironmentCost rCDSOProductionEnvironmentCost;
    
    @JsonProperty("RCDSO - Development & UAT Environment Cost")
    private RCDSODevelopmentUATEnvironmentCost rCDSODevelopmentUATEnvironmentCost;
    
    @JsonProperty("RCDSO - Total Cost for Prod - Compugen Managed")
    private RCDSOTotalCostForProdCompugenManaged rCDSOTotalCostForProdCompugenManaged;
    
    @JsonProperty("RCDSO - Virtual Machine Cost")
    private RCDSOVirtualMachineCost rCDSOVirtualMachineCost;
    
    @JsonProperty("RCDSO - Azure File Storage Cost")
    private RCDSOAzureFileStorageCost rCDSOAzureFileStorageCost;
    
    @JsonProperty("RCDSO - Azure Backup and Site Recovery")
    private RCDSOAzureBackupAndSiteRecovery rCDSOAzureBackupAndSiteRecovery;
    
    @JsonProperty("RCDSO - Azure App Services Cost")
    private RCDSOAzureAppServicesCost rCDSOAzureAppServicesCost;
}
/********************** RCDSOProductionEnvironmentCost.java *************************/
@Getter
@Setter
public class RCDSOProductionEnvironmentCost {
    @JsonProperty("href")
    private String href;
}
/********************** RCDSODevelopmentUATEnvironmentCost.java *************************/
@Getter
@Setter
public class RCDSODevelopmentUATEnvironmentCost {
    @JsonProperty("href")
    private String href;
}
/********************** RCDSOTotalCostForProdCompugenManaged.java *************************/
@Getter
@Setter
public class RCDSOTotalCostForProdCompugenManaged {
    @JsonProperty("href")
    private String href;
}
/********************** RCDSOVirtualMachineCost.java *************************/
@Getter
@Setter
public class RCDSOVirtualMachineCost {
    @JsonProperty("href")
    private String href;
}
/********************** RCDSOAzureFileStorageCost.java *************************/
@Getter
@Setter
public class RCDSOAzureFileStorageCost {
    @JsonProperty("href")
    private String href;

}
/********************** RCDSOAzureBackupAndSiteRecovery.java *************************/
@Getter
@Setter
public class RCDSOAzureBackupAndSiteRecovery {
    @JsonProperty("href")
    private String href;

}
/********************** RCDSOAzureAppServicesCost.java *************************/
@Getter
@Setter
public class RCDSOAzureAppServicesCost {
    @JsonProperty("href")
    private String href;

}

所以现在，在我的应用程序中向客户端发送响应之前。 我想从此响应中获取数据并想进行一些操作并将其转换为自定义 POJO class。我尝试使用 JSONObject 但出现了一些异常。

我想使用 AJAX 在 HTML 表中显示这个 JSON 数据。

那么我应该如何从上面的 JSON 中提取或获取个人数据呢？

Answer 1

基于 JSON 结构，假设您有以下 POJO：

public class Report implements Serializable {
    private Map<String, Link> links;
    // getters, setters
}

public class Link {
    private String href;
    // getters, setters
}

现在不是将响应主体提取为 JSON String ，而是直接将其转换为 POJO。

public Report getReportListByClientId(String clientId) {
        
        ResponseEntity<Report> responseEntity = null;
        
        try {
            ..
            responseEntity = restTemplate.exchange(uri, HttpMethod.GET, requestEntity, Report.class);
            
            return responseEntity.getBody();

        } catch (Exception e) {
           ..
        }
}

假设：该项目在类路径中有Jackson ，因此默认情况下将启用MappingJacksonHttpMessageConverter和RestTemplate以使上述方法起作用。

Answer 2

我会尽力帮助你。 您可以使用 JsonPath 来操作您的字符串 json。

    <dependency>
        <groupId>com.jayway.jsonpath</groupId>
        <artifactId>json-path</artifactId>
        <version>2.7.0</version>
    </dependency>

将此库添加到您的代码中，然后尝试使用它

        String json = """
            {
                "links": {
                    "RCDSO - Production Environment Cost": {
                        "href": "href 1"
                    },
                    "RCDSO - Development & UAT Environment Cost": {
                        "href": "href 2"
                    },
                    "RCDSO - Total Cost for Prod - Compugen Managed": {
                        "href": "href 3"
                    },
                    "RCDSO - Virtual Machine Cost": {
                        "href": "href 4"
                    },
                    "RCDSO - Azure File Storage Cost": {
                        "href": "href 5"
                    },
                    "RCDSO - Azure Backup and Site Recovery": {
                        "href": "href 6"
                    },
                    "RCDSO - Azure App Services Cost": {
                        "href": "href 7"
                    }
                }
            }
            """;
    Map<String, Map<String, String>> links = JsonPath.read(json, "$.links");
    links.forEach((key, value) -> {
        System.out.println("k = " + key);
        System.out.print("v = ");
        value.forEach((key2, value2) -> {
            System.out.println("key = " + key2 + " : value = " + value2);
        });
    });