解析JSON文件Java

Question

我想在java中解析一个JSON文件,并从下面提到的文件中获取以下值:

{
  "status": "OK",
  "origin_addresses": [ "Vancouver, BC, Canada", "Seattle, État de Washington, États-Unis" ],
  "destination_addresses": [ "San Francisco, Californie, États-Unis", "Victoria, BC, Canada" ],
  "rows": [ {
    "elements": [ {
      "status": "OK",
      "duration": {
        "value": 340110,
        "text": "3 jours 22 heures"
      },
      "distance": {
        "value": 1734542,
        "text": "1 735 km"
      }
    }, {
      "status": "OK",
      "duration": {
        "value": 24487,
        "text": "6 heures 48 minutes"
      },
      "distance": {
        "value": 129324,
        "text": "129 km"
      }
    } ]
  }, {
    "elements": [ {
      "status": "OK",
      "duration": {
        "value": 288834,
        "text": "3 jours 8 heures"
      },
      "distance": {
        "value": 1489604,
        "text": "1 490 km"
      }
    }, {
      "status": "OK",
      "duration": {
        "value": 14388,
        "text": "4 heures 0 minutes"
      },
      "distance": {
        "value": 135822,
        "text": "136 km"
      }
    } ]
  } ]
}

从每个元素,我想得到距离和持续时间的值字段.我该怎么做呢？

Answer 1

使用json.org参考实现(org.json主页,在此处下载).代码有点乱,但我认为它符合您的要求.您可以通过不创建所有这些对象而是直接访问它们来获取大量快捷方式.我这样做的原因是试图让它更容易跟踪发生的事情.

package com.mypackage;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class Main {
    public static void main(String[] args) {
        String jsonStr = "{\"status\": \"OK\",\"origin_addresses\": [ \"Vancouver, BC, Canada\", \"Seattle, État de Washington, États-Unis\" ],\"destination_addresses\": [ \"San Francisco, Californie, États-Unis\", \"Victoria, BC, Canada\" ],\"rows\": [ {\"elements\": [ {\"status\": \"OK\",\"duration\": {\"value\": 340110,\"text\": \"3 jours 22 heures\"},\"distance\": {\"value\": 1734542,\"text\": \"1 735 km\"}}, {\"status\": \"OK\",\"duration\": {\"value\": 24487,\"text\": \"6 heures 48 minutes\"},\"distance\": {\"value\": 129324,\"text\": \"129 km\"}} ]}, {\"elements\": [ {\"status\": \"OK\",\"duration\": {\"value\": 288834,\"text\": \"3 jours 8 heures\"},\"distance\": {\"value\": 1489604,\"text\": \"1 490 km\"}}, {\"status\": \"OK\",\"duration\": {\"value\": 14388,\"text\": \"4 heures 0 minutes\"},\"distance\": {\"value\": 135822,\"text\": \"136 km\"}} ]} ]}";

        try {
            JSONObject rootObject = new JSONObject(jsonStr); // Parse the JSON to a JSONObject
            JSONArray rows = rootObject.getJSONArray("rows"); // Get all JSONArray rows

            for(int i=0; i < rows.length(); i++) { // Loop over each each row
                JSONObject row = rows.getJSONObject(i); // Get row object
                JSONArray elements = row.getJSONArray("elements"); // Get all elements for each row as an array

                for(int j=0; j < elements.length(); j++) { // Iterate each element in the elements array
                    JSONObject element =  elements.getJSONObject(j); // Get the element object
                    JSONObject duration = element.getJSONObject("duration"); // Get duration sub object
                    JSONObject distance = element.getJSONObject("distance"); // Get distance sub object

                    System.out.println("Duration: " + duration.getInt("value")); // Print int value
                    System.out.println("Distance: " + distance.getInt("value")); // Print int value
                }
            }
        } catch (JSONException e) {
            // JSON Parsing error
            e.printStackTrace();
        }
    }
}

Answer 2

1. 创建一个反映JSON的类结构
2. 使用像Jackson或GSON这样的库将json反序列化为类的实例.

如果你想要一个更动态的方法,上面的框架也可以序列化到地图.