如何从JsonNode获取键值映射？

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class JsonNodeExample {
    public static void main(String[] args) {
        String json = "{\"name\":\"John\", \"age\":30, \"city\":\"New York\"}";

        try {
            ObjectMapper objectMapper = new ObjectMapper();
            JsonNode jsonNode = objectMapper.readTree(json);

            Map<String, String> keyValueMap = new HashMap<>();

            Iterator<Map.Entry<String, JsonNode>> fields = jsonNode.fields();
            while (fields.hasNext()) {
                Map.Entry<String, JsonNode> entry = fields.next();
                String key = entry.getKey();
                String value = entry.getValue().asText();
                keyValueMap.put(key, value);
            }

            // 打印键值映射
            for (Map.Entry<String, String> entry : keyValueMap.entrySet()) {
                System.out.println("Key: " + entry.getKey() + ", Value: " + entry.getValue());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}