我正在阅读 JSON ReST API。和 JSON 看起来不同第一个看起来像这样：
processJSON({
"TripList":{
"noNamespaceSchemaLocation":"http://api.vasttrafik.se/v1/hafasRestTrip.xsd",
"servertime":"10:39",
"serverdate":"2013-04-04",
"Trip":[{
"Leg":[{
"name":"Buss 761",
"type":"BUS",
"id":"9015014576100035",
"direction":"Heden via Linnéplatsen",
"fgColor":"#00A5DC",
"bgColor":"#ffffff",
"stroke":"Solid",
"Origin":{
"name":"Hökegårdsgatan, Mölndal",
"type":"ST",
"id":"9022014012273002",
"routeIdx":"30",
"time":"10:42",
"date":"2013-04-04",
"track":"B ",
"$":"\n"
}
第二个是这样的：
processJSON({
"TripList":{
"noNamespaceSchemaLocation":"http://api.vasttrafik.se/v1/hafasRestTrip.xsd",
"servertime":"10:46",
"serverdate":"2013-04-04",
"Trip":[{
"Leg":{
"name":"Spårvagn 8",
"type":"TRAM",
"id":"9015014500800075",
"direction":"Angered",
"fgColor":"#872387",
"bgColor":"#ffffff",
"stroke":"Solid",
"accessibility":"wheelChair",
"Origin":{
"name":"Korsvägen, Göteborg",
"type":"ST",
"id":"9022014003980005",
"routeIdx":"12",
"time":"10:50",
"date":"2013-04-04",
"track":"E ",
"rtTime":"10:51",
"rtDate":"2013-04-04",
"$":"\n"
}
现在我想做的是如果 JSON“腿”是一个数组，我会循环到数组中并获取数据。但是如果“腿”是一个对象，那么循环就没有用了，我可以挖掘并获取数据。这个对我有用
但是第一个不起作用并给出了空指针期望。
我的代码是：
public class ParseTimeTable {
String temp = "";
public void parseJsonData() throws ParseException, IOException {
JSONParser parser = new JSONParser();
Object obj = parser.parse(Planner.getPlanner().getJsonDataForTrip(
Planner.getPlanner().getStartLocationID(),
Planner.getPlanner().getDestinationID()));
JSONObject topObject = (JSONObject) obj;
JSONObject tripList = (JSONObject) topObject.get("TripList");
JSONArray array = (JSONArray) tripList.get("Trip");
Iterator<JSONObject> iterator = array.iterator();
while (iterator.hasNext()) {
JSONObject jsonObj = iterator.next();
if (jsonObj.get("Leg") instanceof JSONArray)
{
JSONArray array2 = (JSONArray) tripList.get("Leg");
Iterator<JSONObject> iterator2 = array2.iterator();
while (iterator2.hasNext()) {
String line = (String) jsonObj.get("name");
String direction = (String) jsonObj.get("direction");
JSONObject origin = (JSONObject) jsonObj.get("Origin");
String name = (String) origin.get("name");
String time = (String) origin.get("time");
String track = (String) origin.get("track");
JSONObject destination = (JSONObject) jsonObj.get("Destination");
String dname = (String) destination.get("name");
String dtime = (String) destination.get("time");
String dtrack = (String) destination.get("track");
temp = line + " " + "Mot : " + direction + " " + "Från : "
+ name + " " + "Avgång : " + time + " "
+ "Track : " + track + "- " + "Destination : "
+ dname + " " + "Ankomst : " + dtime + " "
+ "Track : " + dtrack;
TripService.getTrip().setList(temp);
}
}
else {
jsonObj = (JSONObject) jsonObj.get("Leg");
String line = (String) jsonObj.get("name");
String direction = (String) jsonObj.get("direction");
JSONObject origin = (JSONObject) jsonObj.get("Origin");
String name = (String) origin.get("name");
String time = (String) origin.get("time");
String track = (String) origin.get("track");
JSONObject destination = (JSONObject) jsonObj.get("Destination");
String dname = (String) destination.get("name");
String dtime = (String) destination.get("time");
String dtrack = (String) destination.get("track");
temp = line + " " + "Mot : " + direction + " " + "Från : "
+ name + " " + "Avgång : " + time + " " + "Track : "
+ track + "- " + "Destination : " + dname + " "
+ "Ankomst : " + dtime + " " + "Track : " + dtrack;
TripService.getTrip().setList(temp);
}
}
}
}
因此，我的 else 语句中的所有内容都按应有的方式工作，但在我的 if 语句中，我得到了一个空指针，因为 array2 是空的。所以给我空指针的是我的第二个数组： JSONArray array2 = (JSONArray) tripList.get("腿”）;
为什么会这样？
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at se.lowdin.trafficPlanner.ParseTimeTable.parseJsonData(ParseTimeTable.java:35)
at se.lowdin.trafficPlanner.MainWindow$UpdateAction.actionPerformed(MainWindow.java:294)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)