如何使用 Jsonb 将 JSON 中的数值数组解析为 Java 对象

问题描述

我喜欢使用 Jsonb 将 JSON 数据映射到 Java 对象是多么容易，但我似乎偶然发现了一个没有很好记录的用例......

给定这个json数据：

<input type="number" id="a" oninput="calculate()" /> × 588 +
<input type="number" id="b" oninput="calculate()" /> × 28 +
<input type="number" id="c" oninput="calculate()" /> + 44032 =
<input type='text' id="result" readonly />

什么可以用作存储点值的对象类型？

kong migrations bootstrap

所以我可以创建临时对象：

{
  "id": "test","points": [
    [
      -24.787439346313477,5.5551919937133789
    ],[
      -23.788913726806641,6.7245755195617676
    ],[
      -22.257251739501953,7.2461895942687988
    ]
  ]
}

到目前为止，我已经尝试了以下方法：

• import jakarta.json.bind.annotation.JsonbProperty; public class Temp { @JsonbProperty("id") private String id; @JsonbProperty("points") private ??? points; // Getters-Setters } --> “无法将 JSON 数组反序列化为：class java.awt.Point”
• import jakarta.json.bind.Jsonb; import jakarta.json.bind.JsonbBuilder; Jsonb jsonb = JsonbBuilder.create(); Temp temp = jsonb.fromJson(jsonString,Temp.class); --> “无法将 JSON 数组反序列化为：class java.awt.Point2D”

解决方法

让我们试试吧：

@Data
public class Temp {
    @JsonbProperty("id")
    private String id;
    
    @JsonbProperty("points")
    private List<List<BigDecimal>> points;
    
    public static void main(String[] args) {
        String jsonString = "{\n" +
                            "  \"id\": \"test\",\n" +
                            "  \"points\": [\n" +
                            "    [\n" +
                            "      -24.787439346313477,\n" +
                            "      5.5551919937133789\n" +
                            "    ],\n" +
                            "    [\n" +
                            "      -23.788913726806641,\n" +
                            "      6.7245755195617676\n" +
                            "    ],\n" +
                            "    [\n" +
                            "      -22.257251739501953,\n" +
                            "      7.2461895942687988\n" +
                            "    ]\n" +
                            "  ]\n" +
                            "}";
        Jsonb jsonb = JsonbBuilder.create();
        Temp temp = jsonb.fromJson(jsonString,Temp.class);
        System.out.println(temp);
    }
}

,

要找出默认映射，请使用非通用字段并使用调试器观察它：

public class Test {
  public static void main(String[] args) {
    String json = "{\"id\":\"test\",\"points\":[[-24.787439346313477,5.555191993713379],[-23.78891372680664,6.724575519561768],[-22.257251739501953,7.246189594268799]]}";
    Temp temp = JsonbBuilder.create().fromJson(json,Temp.class);
    System.out.println(temp.points);
  }

  public static class Temp {
    public String id     = null;
    public List   points = null;

    public Temp() {
    }
  }
}

,

因为我已经这样做了：更改 json 格式将允许这样做：

public class Test {
  public static void main(String[] args) {
    String json = "{\"id\":\"test\",\"points\":[ {\"x\" : 1.0,\"y\" : 2.0 },{\"x\" : 3.0,\"y\" : 4.0 } ] }";
    Temp temp = JsonbBuilder.create().fromJson(json,Temp.class);
    System.out.println(temp.points);
  }

  public static class Temp {
    public String      id     = null;
    public List<Point> points = null;
    public Temp() { }
  }

  public static class Point {
    public double x;
    public double y;
    public Point() { }
  }
}