用Jackson&从json文件解析内容的问题消息-JsonMappingException-无法从START_ARRAY令牌中反序列化 [英] Issue with parsing the content from json file with Jackson & message- JsonMappingException -Cannot deserialize as out of START_ARRAY token

问题描述

给出以下.json文件:

Given the following .json file:

[
    {
        "name" : "New York",
        "number" : "732921",
        "center" : [
                "latitude" : 38.895111, 
                "longitude" : -77.036667
            ]
    },
    {
        "name" : "San Francisco",
        "number" : "298732",
        "center" : [
                "latitude" : 37.783333, 
                "longitude" : -122.416667
            ]
    }
]

我准备了两个类来表示所包含的数据:

I prepared two classes to represent the contained data:

public class Location {
    public String name;
    public int number;
    public GeoPoint center;
}

...

public class GeoPoint {
    public double latitude;
    public double longitude;
}

为了解析.json文件中的内容，我使用 Jackson 2.2.x 并准备了以下方法:

In order to parse the content from the .json file I use Jackson 2.2.x and prepared the following method:

public static List<Location> getLocations(InputStream inputStream) {
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        TypeFactory typeFactory = objectMapper.getTypeFactory();
        CollectionType collectionType = typeFactory.constructCollectionType(
                                            List.class, Location.class);
        return objectMapper.readValue(inputStream, collectionType);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

只要我省略center属性，就可以解析所有内容.但是，当我尝试解析地理坐标时，出现以下错误消息:

As long as I leave out the center property all content can be parsed. However, when I try to parse the geo-coordinates I end up with the following error message:

com.fasterxml.jackson.databind.JsonMappingException:无法反序列化
的实例 com.example.GeoPoint不在START_ARRAY令牌中，位于[来源:android.content.res.AssetManager$AssetInputStream@416a5850;行:5，列:25]
(通过参考链:com.example.Location ["center"])

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of
com.example.GeoPoint out of START_ARRAY token at [Source: android.content.res.AssetManager$AssetInputStream@416a5850; line: 5, column: 25]
(through reference chain: com.example.Location["center"])

推荐答案

您的JSON字符串格式不正确:center的类型是无效对象的数组.在longitude和latitude周围的JSON字符串中将[和]替换为{和}，这样它们将成为对象:

Your JSON string is malformed: the type of center is an array of invalid objects. Replace [ and ] with { and } in the JSON string around longitude and latitude so they will be objects:

[
    {
        "name" : "New York",
        "number" : "732921",
        "center" : {
                "latitude" : 38.895111, 
                "longitude" : -77.036667
            }
    },
    {
        "name" : "San Francisco",
        "number" : "298732",
        "center" : {
                "latitude" : 37.783333, 
                "longitude" : -122.416667
            }
    }
]

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