在Dart与Flutter中提取指定JSON字段转换为Map的方法

下面针对几种主流编程语言，给出具体实现方案：

Java #

方式1：使用 Jackson 库 #

先确保项目中引入Jackson依赖：

<!-- Maven 依赖 -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.2</version>
</dependency>

代码实现：

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.HashMap;
import java.util.Map;

public class JsonExtractor {
    public static void main(String[] args) throws Exception {
        String jsonStr = "{\"_id\":\"_gz-cfmqA1mr\",\"name\":\"Alexander Pope\",\"link\":\"https://en.wikipedia.org/wiki/Alexander_Pope\",\"bio\":\"Alexander Pope (21 May 1688 – 30 May 1744) is regarded as one of the greatest English poets...\",\"description\":\"English poet\",\"quoteCount\":3,\"slug\":\"alexander-pope\",\"dateAdded\":\"2020-12-19\",\"dateModified\":\"2020-12-19\"}";
        
        ObjectMapper objectMapper = new ObjectMapper();
        JsonNode jsonNode = objectMapper.readTree(jsonStr);
        
        Map<String, Object> resultMap = new HashMap<>();
        resultMap.put("name", jsonNode.get("name").asText());
        resultMap.put("quoteCount", jsonNode.get("quoteCount").asInt());
        resultMap.put("slug", jsonNode.get("slug").asText());
        
        // 输出结果
        System.out.println(resultMap);
    }
}

方式2：使用 Gson 库 #

引入Gson依赖：

<!-- Maven 依赖 -->
<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.10.1</version>
</dependency>

代码实现：

import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import java.util.HashMap;
import java.util.Map;

public class GsonJsonExtractor {
    public static void main(String[] args) {
        String jsonStr = "{\"_id\":\"_gz-cfmqA1mr\",\"name\":\"Alexander Pope\",\"link\":\"https://en.wikipedia.org/wiki/Alexander_Pope\",\"bio\":\"Alexander Pope (21 May 1688 – 30 May 1744) is regarded as one of the greatest English poets...\",\"description\":\"English poet\",\"quoteCount\":3,\"slug\":\"alexander-pope\",\"dateAdded\":\"2020-12-19\",\"dateModified\":\"2020-12-19\"}";
        
        JsonObject jsonObject = JsonParser.parseString(jsonStr).getAsJsonObject();
        
        Map<String, Object> resultMap = new HashMap<>();
        resultMap.put("name", jsonObject.get("name").getAsString());
        resultMap.put("quoteCount", jsonObject.get("quoteCount").getAsInt());
        resultMap.put("slug", jsonObject.get("slug").getAsString());
        
        System.out.println(resultMap);
    }
}

Python #

Python自带的json模块即可完成，无需额外依赖：

import json

json_str = '''
{
    "_id": "_gz-cfmqA1mr",
    "name": "Alexander Pope",
    "link": "https://en.wikipedia.org/wiki/Alexander_Pope",
    "bio": "Alexander Pope (21 May 1688 – 30 May 1744) is regarded as one of the greatest English poets...",
    "description": "English poet",
    "quoteCount": 3,
    "slug": "alexander-pope",
    "dateAdded": "2020-12-19",
    "dateModified": "2020-12-19"
}
'''

# 解析JSON为字典
data = json.loads(json_str)

# 提取指定字段到新字典（Python中字典等价于Map）
result_map = {key: data[key] for key in ['name', 'quoteCount', 'slug']}

print(result_map)

JavaScript/Node.js #

在JS中，解析后的JSON对象本身就可以当作Map使用，也可以转为标准Map类型：

const jsonStr = `{
    "_id": "_gz-cfmqA1mr",
    "name": "Alexander Pope",
    "link": "https://en.wikipedia.org/wiki/Alexander_Pope",
    "bio": "Alexander Pope (21 May 1688 – 30 May 1744) is regarded as one of the greatest English poets...",
    "description": "English poet",
    "quoteCount": 3,
    "slug": "alexander-pope",
    "dateAdded": "2020-12-19",
    "dateModified": "2020-12-19"
}`;

// 解析JSON
const data = JSON.parse(jsonStr);

// 方式1：提取为普通对象
const resultObj = {
    name: data.name,
    quoteCount: data.quoteCount,
    slug: data.slug
};

// 方式2：转换为标准Map类型
const resultMap = new Map([
    ['name', data.name],
    ['quoteCount', data.quoteCount],
    ['slug', data.slug]
]);

console.log(resultObj);
console.log(resultMap);

内容的提问来源于stack exchange，提问作者Abhijeet Saroha