Java中的JSON Deserialzer或转换器

Question

我有一个JSON结构：

{
  "dataArray": [
    {
      "key": "prodData",
      "format": "dataCollection",
      "data": [
        {
          "key": "reference",
          "format": "vector",
          "type": "str",
          "data": [
            "SAM",
            "PETER",
            "SMITH"
          ]
        },
        {
          "key": "rank",
          "format": "vector",
          "type": "str",
          "data": [
            "1st",
            "2nd",
            "3rd"
          ]
        },
        {
          "key": "designation",
          "format": "vector",
          "type": "str",
          "data": [
            "MGR",
            "DIR",
            "JNR"
          ]
        },
        {
          "key": "salary",
          "format": "vector",
          "type": "float",
          "data": [
            "2.1",
            "3.1",
            "1.1"
          ]
        }
      ]
    }
  ]
}

而且我想从上述结构中创建Java对象，例如：

Data ("SAM", "1st", "MGR", 2.1)
Data ("PETER", "2nd", "DIR", 3.1)
Data ("SMITH", "3rd", "JNR", 1.1)

[请让我知道Java中的哪个库会自动执行此转换。我不想对单个数组进行任何循环，请分享任何示例。谢谢

Answer 1

根据您的目标和结构，有很多不同的选择。 JSON-B和Jackson是较常见的。

根据您要尝试执行的操作，某些框架甚至以透明的方式执行此操作。例如Quarkus和Spring Boot具有相应的依赖性。

Answer 2

因此，您可以使用com.fasterxml.jackson.core将String转换为类对象，然后使用for循环获取所需的数据。下面是该代码：

您执行所有工作的主要方法：

public static void main(String[] args) throws Exception {
    String input = "{\"dataArray\":[{\"key\":\"prodData\",\"format\":\"dataCollection\",\"data\":[{\"key\":\"reference\",\"format\":\"vector\",\"type\":\"str\",\"data\":[\"SAM\",\"PETER\",\"SMITH\"]},{\"key\":\"rank\",\"format\":\"vector\",\"type\":\"str\",\"data\":[\"1st\",\"2nd\",\"3rd\"]},{\"key\":\"designation\",\"format\":\"vector\",\"type\":\"str\",\"data\":[\"MGR\",\"DIR\",\"JNR\"]},{\"key\":\"salary\",\"format\":\"vector\",\"type\":\"float\",\"data\":[\"2.1\",\"3.1\",\"1.1\"]}]}]}";

    ObjectMapper mapper = new ObjectMapper();

    RootData rootData = mapper.readValue(input, RootData.class);

    List<DataModel> dataModels = rootData.dataArray.get(0).data;

    Collection<Destination> output = convertToDataModel(dataModels);

    // puts out all you need
}

private static Collection<Destination> convertToDataModel(List<DataModel> dataModels) {

    Map<Integer, Map<String, String>> target = new HashMap<>();

    for (DataModel dataModel : dataModels) {
        int counter = 0;
        for (String data : dataModel.data) {

            if (!target.containsKey(counter))
                target.put(counter, new HashMap<>());

            target.get(counter).put(dataModel.key, data);
            counter++;
        }
    }

    return target.values().stream()
            .map(fields -> new Destination(fields.get("reference"), fields.get("rank"), fields.get("designation"), fields.get("salary")))
            .collect(Collectors.toList());

}

---

如果要处理dataArray的所有元素，而不仅是第一个元素（因为JSON仅具有一个元素，则可以用以下命令替换输出行：

Collection<Destination> allOutputs = rootData.dataArray.stream()
            .map(x-> convertToDataModel(x.data))
            .flatMap(Collection::stream) // remove this line if you want a collection of collection instead of a single collection of the Destination
            .collect(Collectors.toList()); 

您的JSON数据的类结构

public class RootData {

    @JsonProperty("dataArray")
    private List<SubRootData> dataArray;

}

public class SubRootData {

    @JsonProperty("key")
    private String key;

    @JsonProperty("format")
    private String format;

    @JsonProperty("data")
    private List<DataModel> data;
}

public class DataModel {

    @JsonProperty("key")
    private String key;

    @JsonProperty("format")
    private String format;

    @JsonProperty("type")
    private String type;

    @JsonProperty("data")
    private Collection<String> data;

}

您的输出类别：

public static class Destination {

    private String reference;

    private String rank;

    private String designation;

    private String salary;


    public Destination(String reference, String rank, String designation, String salary) {
        this.reference = reference;
        this.rank = rank;
        this.designation = designation;
        this.salary = salary;
    }
}