如何解析Java中的JSONArray中的JSONObjects？
问题描述：
我试图从Floodlight（一种SDN控制器）REST API读取数据，并将其输入到其他软件的REST API中。我有这个从泛光灯的REST API写着：如何解析Java中的JSONArray中的JSONObjects？
private JSONArray getFlData(String path) {
try {
logger.info("getData URL: " + path);
URL url = new URL("http://localhost:8080" + path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setDoInput(true);
conn.setRequestMethod("GET");
BufferedReader br = new BufferedReader(
new InputStreamReader(conn.getInputStream()));
String inputline;
StringBuffer response = new StringBuffer();
while((inputline = br.readLine()) != null) {
response.append(inputline);
}
JSONArray jsonr = new JSONArray(response.toString());
br.close();
conn.disconnect();
return jsonr;
}
catch (MalformedURLException e) {
logger.info("Bad URL (getData) " + path);
}
catch (IOException e) {
logger.info("IOException (getData)" + path);
}
catch (JSONException e) {
logger.info("Bad JSON (getData)" + path);
}
return null;
}
然后我解析这些信息纳入名单：
JSONArray flswitches = getFlData("/wm/core/controller/switches/json");
List<String> switchDPIDlist = new ArrayList<String>();
List<String> switchIPlist = new ArrayList<String>();
for (int i = 0;i < flswitches.length();i++){
try {
switchDPIDlist.add(flswitches.getJSONObject(i).getString("switchDPID"));
switchIPlist.add(flswitches.getJSONObject(i).getString("inetAddress"));
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
其中一期工程。但是，当我尝试对网络中的主机输出做同样的事情时，我遇到了问题。作为参考，这里的卷曲输出简单的事情，我可以做到这一点：
curl http://127.0.0.1:8080/wm/core/controller/switches/json
[{"inetAddress":"/127.0.0.1:43663","connectedSince":1456305460978,"switchDPID":"00:00:00:00:00:00:00:01"},{"inetAddress":"/127.0.0.1:43664","connectedSince":1456305460981,"switchDPID":"00:00:00:00:00:00:00:03"},{"inetAddress":"/127.0.0.1:43665","connectedSince":1456305460984,"switchDPID":"00:00:00:00:00:00:00:02"}]
但是，当我试图像这样的更加复杂的输出使用它，我碰到的问题：
curl http://127.0.0.1:8080/wm/device/
[{"entityClass":"DefaultEntityClass","mac":["86:2b:a2:f1:2b:9c"],"ipv4":["10.0.0.1"],"ipv6":[],"vlan":["0x0"],"attachmentPoint":[{"switchDPID":"00:00:00:00:00:00:00:02","port":1,"errorStatus":null}],"lastSeen":1456312407529},{"entityClass":"DefaultEntityClass","mac":["1e:94:63:67:1e:d1"],"ipv4":["10.0.0.3"],"ipv6":[],"vlan":["0x0"],"attachmentPoint":[{"switchDPID":"00:00:00:00:00:00:00:03","port":1,"errorStatus":null}],"lastSeen":1456312407625},{"entityClass":"DefaultEntityClass","mac":["06:d7:e0:c5:60:86"],"ipv4":["10.0.0.2"],"ipv6":[],"vlan":["0x0"],"attachmentPoint":[{"switchDPID":"00:00:00:00:00:00:00:02","port":2,"errorStatus":null}],"lastSeen":1456312407591},{"entityClass":"DefaultEntityClass","mac":["6e:c3:e4:5e:1f:65"],"ipv4":["10.0.0.4"],"ipv6":[],"vlan":["0x0"],"attachmentPoint":[{"switchDPID":"00:00:00:00:00:00:00:03","port":2,"errorStatus":null}],"lastSeen":1456312407626}]
出于某种原因，仅将.getString（“switchDPID”）更改为.getString（“mac”）不起作用。显然，使用“mac”的结果不是一个字符串，我无法弄清楚我应该使用什么。我在这里做错了什么，我应该改变什么？这是mac地址格式的问题还是与JSON格式有关？
答
mac是一个JSON数组。
在该第一示例中，层次结构是如下
JSON阵列 - > JSON对象 - > switchDPID
在第二个层次是
JSON阵列 - > JSON对象 - > JSON数组（mac） - > mac内的数据。
如果您在树形结构中看到JSON，则可以看到差异。 我使用http://www.jsoneditoronline.org/
您将不得不首先获取JSON数组（mac），然后访问它的数据的第一个元素。
答
这里，mac是一个数组。尝试读取它作为一个数组，然后获取数组中的第一个项目作为字符串！
你可以看看杰克逊API，这里提到的例子是http://www.mkyong.com/java/jackson-2-convert-java-object-to-from-json/ – Rupesh