使用 Jackson 2 解组 json 时出错

Question

我正在尝试使用 Jackson 2 解组以下 JSON 文件：

{
  "mapID": "123",
  "objects": [
    {
      "mapID": "123",
      "objectID": "12",
      "properties": {
        "type": "2",
        "maxSpeed": "110",
        "name": "name1",
        "bridge": false
      },
      "geometry": {
        "coordinates": [
          {
            "latitude" : 4.54559326171875,
            "longitude" : 45.754109791149865
          },
          {
            "latitude" : 4.54559326171875,
            "longitude" : 45.754109791149865
          },
          {
            "latitude" : 4.54559326171875,
            "longitude" : 45.754109791149865
          },
          {
            "latitude" : 4.54559326171875,
            "longitude" : 45.754109791149865
          }
        ]
      }
    },
    {
      "mapID": "123",
      "objectID": "14",
      "properties": {
        "type": "5",
        "name": "name2",
        "redLightTime": "40"
      },
      "geometry": {
        "coordinates": [
          {
            "latitude" : 4.54559326171875,
            "longitude" : 45.754109791149865
          }
        ]
      }
    },
    {
      "mapID" : "123",
      "objectID" : "13",
      "properties" : {
        "type" : "4",
        "maxSpeed" : "40",
        "name" : "name3",
        "roundaboutLanes" : "2"
      },
      "geometry": {
        "coordinates" : [
          [
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            },
            {
              "latitude" : 4.54559326171875,
              "longitude" : 45.754109791149865
            }
          ]
        ]
      }
    }
  ]
}

public class MapJSON {
    private int mapID;
    private List<Objects> objects;

    public int getMapID() {
        return mapID;
    }

    public void setMapID(int mapID) {
        this.mapID = mapID;
    }

    public List<Objects> getObjects() {
        return objects;
    }

    public void setObjects(List<Objects> objects) {
        this.objects = objects;
    }
}


public class Objects {
    private int mapID;
    private int objectID;
    private Properties properties;
    private Geometry geometry;

    public int getMapID() {
        return mapID;
    }

    public void setMapID(int mapID) {
        this.mapID = mapID;
    }

    public int getObjectID() {
        return objectID;
    }

    public void setObjectID(int objectID) {
        this.objectID = objectID;
    }

    public Properties getProperties() {
        return properties;
    }

    public void setProperties(Properties properties) {
        this.properties = properties;
    }

    public Geometry getGeometry() {
        return geometry;
    }

    public void setGeometry(Geometry geometry) {
        this.geometry = geometry;
    }
}


public class Geometry {

    private List<Coordinates> coordinates;

    public List<Coordinates> getCoordinates() {
        return coordinates;
    }

    public void setCoordinates(List<Coordinates> coordinates) {
        this.coordinates = coordinates;
    }
}

public class Coordinates {

    private Double latitude;
    private Double longitude;

    public Double getLatitude() {
        return latitude;
    }

    public void setLatitude(Double latitude) {
        this.latitude = latitude;
    }

    public Double getLongitude() {
        return longitude;
    }

    public void setLongitude(Double longitude) {
        this.longitude = longitude;
    }

解组几何/坐标元素时发生错误。 有人能指出错误在哪里吗？

几何部分之前一切正常。

Answer 1

在 json 示例中 coordinates 是双精度数组，但在 java 代码中它是对象数组：

您需要将 JSON 调整为如下格式：

"coordinates": [
          {
            latitude : 4.54559326171875,
            longitude : 45.754109791149865
          }
        ]

或考虑更改您的Coordinates 类以反映 JSON 结构：

public class Coordinates {
    private List<Double> coordinates;
}

Answer 2

您的课程与您的 JSON 不匹配。

您的 Coordinates 类有两个双字段，latitude 和 longitude，它们将匹配如下所示的 JSON：

  "geometry": {
    "coordinates": [
      {
        "latitude" : 4.54559326171875,
        "longitude" : 45.754109791149865
      },
      ...

另一方面，您的 JSON 将坐标定义为一组嵌套数组：

  "geometry": {
    "coordinates": [
      [
        4.54559326171875,
        45.754109791149865
      ],
      ...

您需要更改 JSON 以传递命名字段，或者更改 你的几何类来存储一个嵌套的 double 列表：

public class Geometry {

    private List<List<Double>> coordinates;
    ...