Question

我有以下JSON我需要能够在POJO中呈现，我怎么能这样做？

JSON每天有一个密钥，每个密钥的值是两个独立的逻辑阵列，我使用的是Jackson库。

{
  "2014/01/02": [
    {"ABC": 2.25, "XYZ": 4.05},
    {"amazon.com": 3}
  ],
  "2014/01/03": [
    {"ABC": 13.02},
    {"amazon.com": 3}
  ]
}

Answer 1

你没有太多选择。这是一个丑陋的JSON。没有一致的格式，您可以在其中创建POJO。

您需要考虑的事项。这个{}是一个JSON对象。我是Java映射术语，它可以映射到POJO，也可以映射到Map。为了映射到POJO，您需要常见的属性名称和格式，而您似乎并不喜欢它们。这一切似乎都在变化。因此，您可能需要使用Map。这是我看待它的方式

{  // Start Map
  "2014/01/02": [ // Map key: start Array ( List<Map> )
    {"ABC": 2.25, "XYZ": 4.05},  // Start another Map
    {"amazon.com": 3}  // another Map

您可以使用@JsonAnySetter来简化，使用POJO包装器，但最终我仍然会在我的评论中指出Map<String, List<Map<String, Object>>。如果你想要POJO，需要一些常见的格式。

以下是一种让它发挥作用的方法的例子

POJO

public class Dynamic {
    private Map<String, Object> map = new HashMap<>();

    public Object get(String key) {
        return map.get(key);
    }

    public Map<String, Object> getMap() {
        return map;
    }

    @JsonAnySetter
    public void set(String name, Object value) {
        map.put(name, value);
    }
}

测试（在simple.json文件中使用您的确切JSON）

public class Test {

    public static void main(String[] args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        Dynamic dynamic = mapper.readValue(new File("simple.json"), Dynamic.class);
        for (String key : dynamic.getMap().keySet()) {
            System.out.println("key: " + key);
            System.out.println("--------");
            List<Map<String, Object>> list = (List<Map<String, Object>>) dynamic.get(key);
            for (Map<String, Object> map : list) {
                for (Map.Entry<String, Object> entry: map.entrySet()) {
                    System.out.println("key: " + entry.getKey() + ", value: " + entry.getValue());
                }
            }
            System.out.println("========");
        }
    }
}

结果

key: 2014/01/03
--------
key: ABC, value: 13.02
key: amazon.com, value: 3
========
key: 2014/01/02
--------
key: ABC, value: 2.25
key: XYZ, value: 4.05
key: amazon.com, value: 3
========

Answer 2

    {
  "2014/01/02": [
    {"ABC": 2.25, "XYZ": 4.05},
    {}
  ],
  "2014/01/03": [
    {"ABC": 13.02},
    {"amazon.com": 3}
  ]
}
This is even JSON, but not useful. I would make JSON for this like below.
{
  [
     {date: '2014/01/01',data:[{abc: 13.02, "amazonCom": 3},{abc: 13.02, "amazonCom": 3}},
     {date: '2014/01/02',data:[{abc: 13.02, "amazonCom": 3},{abc: 13.02, "amazonCom": 3}},
   ]
}

Java
public jsonObj {

    private String date;
    private List<DateData> data;

   .... setter//getter

}

public class DateData {
   private double abc;
   private int amazoneCom;
    //constructor and getter/setter
}



You can use JSON libraries like below.

1. Jackson - http://jackson.codehaus.org/
2. Gson  - https://code.google.com/p/google-gson/

Those libraries helps you to convert json into Java Object and vise versa as well.

Hope it can help you with solving your problem.

Answer 3

There are many ways to transform json to pojo. Here I am sharing few URL to achieve the same

Google Gson Tutorial : Convert Java Object to / from JSON http://howtodoinjava.com/2014/06/17/google-gson-tutorial-convert-java-object-to-from-json/
Generate Plain Old Java Objects from JSON or JSON-Schema. http://www.jsonschema2pojo.org/

如何将Json转换为POJO

3 个答案: