使用 Java 从 google Weather API 中提取数据 [英] Using Java to extract data from google Weather API
问题描述
2020 年更新 - 请忽略以下问题,因为 Google 的天气 API 不再能够使用.如果您对使用天气 API 感兴趣,Darksky 是大多数人使用的事实:https://darksky.net/dev
2020 update -- Please disregard the question below as Google's weather API is no longer able to be used. If you are interested in using a weather API, Darksky is the defacto that most people use: https://darksky.net/dev
如果您使用 Java,解析 JSON 的正常方法是使用 org.json:https://devqa.io/java/how-to-parse-json-in-java
If you use Java, the normal way to parse the JSON is using org.json: https://devqa.io/java/how-to-parse-json-in-java
--
下面的原始问题.
我最近一直在玩 xml 文档和 java,但我绝对没有使用谷歌天气 API 的运气.
I've been playing around with xml documents and java a bit recently, but I've had absolutely no luck using the google weather API.
假设我正在尝试做一个简单的对象来存储当前温度,并预测明天的温度,我该怎么做?
Let's assume that I'm trying to do a simple object to store current temp, and forecast temp for just tomorrow, how would I do this?
http://www.google.com/ig/api?weather=02110 是我家乡的工作示例.
http://www.google.com/ig/api?weather=02110 Is the working example for my home city.
谢谢
使用此代码:
public static final String[] xmlLoader(){
String xmlData[] = new String[2];
try {
URL googleWeatherXml = new URL("http://www.google.com/ig/api?weather=02110");
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(googleWeatherXml.openStream());
// normalize text representation
doc.getDocumentElement ().normalize ();
NodeList listOfWeek = doc.getElementsByTagName("");
Node firstWeekNode = listOfWeek.item(dateCounter-1);
int totalWeeks = listOfWeek.getLength();
//Break xml file into parts, then break those parts down int an array by passing individual elements to srtings
if(firstWeekNode.getNodeType() == Node.ELEMENT_NODE){
Element firstWeekElement = (Element)firstWeekNode;
//-------
NodeList dateList = firstWeekElement.getElementsByTagName("date");
Element dateElement = (Element)dateList.item(0);
NodeList textDateList = dateElement.getChildNodes();
xmlData[0]= (((Node)textDateList.item(0)).getNodeValue().trim()).toString();
//-------
NodeList riddleList = firstWeekElement.getElementsByTagName("riddle");
Element riddleElement = (Element)riddleList.item(0);
NodeList textRiddleList = riddleElement.getChildNodes();
xmlData[1]= (((Node)textRiddleList.item(0)).getNodeValue().trim()).toString();
//----
NodeList lWSList = firstWeekElement.getElementsByTagName("lastWeekSolution");
Element ageElement = (Element)lWSList.item(0);
NodeList textLWSList = ageElement.getChildNodes();
xmlData[2]= (((Node)textLWSList.item(0)).getNodeValue().trim()).toString();
//------
}//end of if clause
}
catch(MalformedURLException f){System.err.println(f.getMessage()); }
catch(NullPointerException npe){
System.out.println("The Weather Data you searched for is incorrect or does not yet exist, try again. ");
String s[] = {" ", " "};
main(s);
}
catch (SAXParseException err) {
System.out.println ("** Parsing error" + ", line "
+ err.getLineNumber () + ", uri " + err.getSystemId ());
System.out.println(" " + err.getMessage ());
}
catch (SAXException e) {
Exception x = e.getException ();
((x == null) ? e : x).printStackTrace ();
}catch (Throwable t) {
t.printStackTrace ();
}
return xmlData;
}
无论我做什么,都会得到大量的空指针.
Getting tons of null pointers, no matter what I do.
推荐答案
调用 .getElementsByTagName() 时,需要对返回的值进行保护:
When you call .getElementsByTagName(), you need to put a guard on the value you get back:
NodeList dateList = firstWeekElement.getElementsByTagName("date");
if (datelist != null) {
Element dateElement = (Element)dateList.item(0);
等等.
更新
现在我查看了 XML,我发现没有 <date>元素;所以这就是 dateList 为空的原因.你想寻找像 <forecast_information> 这样的元素.和<城市>.
Now that I look at the XML, I see that there are no <date> elements; so that's why dateList is null. You want to be looking for elements like <forecast_information> and <city>.
NodeList forecasts = firstWeekElement.getElementsByTagName("forecast_information");
if (forecasts != null) {
Element forecastElement = (Element)forecasts.item(0);
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