How to convert HashMap value to Java Pojo?

Question

I am working on consuming external API in spring boot application. I have written my JSON response that is coming from external API using RestTemplate and exchange() method of HttpEntity.

Below is the response:

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);
    });
});

In above code, I tried to get values from Map. Now I want to convert into my POJO class.

Below is my Pojo named OlapCustomReportResponse.java:

public class OlapCustomReportResponse {
    private String name;
    private String href;
}

I extracted key from outer loop and on the basis of key I extracted value from inner loop as below:

Key 1 = RCDSO - Production Environment Cost
Key 2 = href : Value 2 = some url related to key 1

Key 2 = RCDSO - Development & UAT Environment Cost
Key 2 = href : Value 2 = some url related to key 2 

Key 3 = RCDSO - Total Cost for Prod - Compugen Managed
Key 2 = href : Value 2 = some url related to key 3

Key 4 = RCDSO - Virtual Machine Cost
Key 2 = href : Value 2 = some url related to key 4 

.... and so on

I want my OlapCustomReportResponse.java should look something like below:

[
  {
    "href" : "some url of key 1",
    "name" : "key 1"
  },
  { 
    "href" : "some url of key 2",
    "name" : "key 2"
  },
  { 
    "href" : "some url of key 3",
    "name" : "key 3"
  },
  { 
    "href" : "some url of key 4",
    "name" : "key 4"
  }
    ...... and so on...
]

My main motivation is to map or convert that result to my POJO class. How should I do or what would be the possible approach?

Answer 1

I am actually using com.fasterxml.jackson.databind.ObjectMapper and it is really fast, strong and a good json parser

ObjectMapper objectMapper = new ObjectMapper();

TypeReference<HashMap<String, Map<String, String>>> typeRef = new TypeReference<HashMap<String, Map<String, String>>>() {};

Map<String, Map<String, String>> results = objectMapper.readValue(file, typeRef);