国家气象局天气预报为我们提供了数据交换格式为JSON的WEB API：http://m.weather.com.cn/data/101210101.html

数字代码代表不同的城市和其它城镇，具体对应关系请查阅博客：http://blog.csdn.net/zgyulongfei/article/details/7956118

我们可以利用URL和HttpURLConnection（在移动平台，比如android，可以使用HttpGet来获取数据流)获取Web Service为我们提供的JSON数据。

但是我们知道Java中都是对象，而JSON是一个有具体格式的字符串，我们需要进行相应的转换。

我们可以利用org.json.*包或者google提供的gson包来解析JSON数据，这里我们使用google的gson包吧。

gson包的下载地址为:

假设我们已经获得了JSON数据，比如：

{"weatherinfo":{"city":"杭州","city_en":"hangzhou","date_y":"2013年2月28日","date":"","week":"星期四","fchh":"11","cityid":"101210101","temp1":"21℃~10℃","temp2":"11℃~4℃","temp3":"6℃~2℃","temp4":"10℃~3℃","temp5":"15℃~3℃","temp6":"16℃~4℃","tempF1":"69.8℉~50℉","tempF2":"51.8℉~39.2℉","tempF3":"42.8℉~35.6℉","tempF4":"50℉~37.4℉","tempF5":"59℉~37.4℉","tempF6":"60.8℉~39.2℉","weather1":"多云转中雨","weather2":"中雨转小雨","weather3":"阴转多云","weather4":"晴转多云","weather5":"晴","weather6":"多云","img1":"1","img2":"8","img3":"8","img4":"7","img5":"2","img6":"1","img7":"0","img8":"1","img9":"0","img10":"99","img11":"1","img12":"99","img_single":"1","img_title1":"多云","img_title2":"中雨","img_title3":"中雨","img_title4":"小雨","img_title5":"阴","img_title6":"多云","img_title7":"晴","img_title8":"多云","img_title9":"晴","img_title10":"晴","img_title11":"多云","img_title12":"多云","img_title_single":"多云","wind1":"东北风小于3级","wind2":"北风小于3级","wind3":"北风小于3级","wind4":"东北风小于3级","wind5":"东北风转东风小于3级","wind6":"东风小于3级","fx1":"东北风","fx2":"东北风","fl1":"小于3级","fl2":"小于3级","fl3":"小于3级","fl4":"小于3级","fl5":"小于3级","fl6":"小于3级","index":"较冷","index_d":"建议着大衣、呢外套加毛衣、卫衣等服装。体弱者宜着厚外套、厚毛衣。因昼夜温差较大，注意增减衣服。","index48":"较冷","index48_d":"建议着厚外套加毛衣等服装。年老体弱者宜着大衣、呢外套加羊毛衫。","index_uv":"最弱","index48_uv":"最弱","index_xc":"不宜","index_tr":"适宜","index_co":"舒适","st1":"22","st2":"10","st3":"9","st4":"2","st5":"5","st6":"2","index_cl":"适宜","index_ls":"适宜","index_ag":"极不易发"}}

注意这是一个JSON字符串，{}代表一个对象，[]代表一个数组，"key":"value"代表对象的一个属性，只要知道这些基本常识就可以了。

现在我们需要在Java中编写该JSON数据对应的POJO类：

观察该JSON数据字符串可以知道，该对象只有一个属性weatherinfo，而weatherinfo又是一个对象，weatherinfo对象包含许多类型为字符串的属性。

先编写最外部的类吧，我们把它命名成WeatherStation:

public class WeatherStation {

	private WeatherInfo weatherinfo;

	public WeatherInfo getWeatherinfo() {
		return weatherinfo;
	}

	public void setWeatherinfo(WeatherInfo weatherinfo) {
		this.weatherinfo = weatherinfo;
	}
}

接下来是编写WeatherInfo类：(这里只写了一部分属性）

public class WeatherInfo {

	private String city;
	private String city_en;
	private String date_y;
	private String date;
	private String week;
	private String fchh;
	private String cityid;
	private String temp1;
	private String temp2;
	private String temp3;
	private String temp4;
	private String temp5;
	private String temp6;
	private String tempF1;
	private String tempF2;
	private String tempF3;
	private String tempF4;
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public String getCity_en() {
		return city_en;
	}
	public void setCity_en(String city_en) {
		this.city_en = city_en;
	}
	public String getDate_y() {
		return date_y;
	}
	public void setDate_y(String date_y) {
		this.date_y = date_y;
	}
	public String getDate() {
		return date;
	}
	public void setDate(String date) {
		this.date = date;
	}
	public String getWeek() {
		return week;
	}
	public void setWeek(String week) {
		this.week = week;
	}
	public String getFchh() {
		return fchh;
	}
	public void setFchh(String fchh) {
		this.fchh = fchh;
	}
	public String getCityid() {
		return cityid;
	}
	public void setCityid(String cityid) {
		this.cityid = cityid;
	}
	public String getTemp1() {
		return temp1;
	}
	public void setTemp1(String temp1) {
		this.temp1 = temp1;
	}
	public String getTemp2() {
		return temp2;
	}
	public void setTemp2(String temp2) {
		this.temp2 = temp2;
	}
	public String getTemp3() {
		return temp3;
	}
	public void setTemp3(String temp3) {
		this.temp3 = temp3;
	}
	public String getTemp4() {
		return temp4;
	}
	public void setTemp4(String temp4) {
		this.temp4 = temp4;
	}
	public String getTemp5() {
		return temp5;
	}
	public void setTemp5(String temp5) {
		this.temp5 = temp5;
	}
	public String getTemp6() {
		return temp6;
	}
	public void setTemp6(String temp6) {
		this.temp6 = temp6;
	}
	public String getTempF1() {
		return tempF1;
	}
	public void setTempF1(String tempF1) {
		this.tempF1 = tempF1;
	}
	public String getTempF2() {
		return tempF2;
	}
	public void setTempF2(String tempF2) {
		this.tempF2 = tempF2;
	}
	public String getTempF3() {
		return tempF3;
	}
	public void setTempF3(String tempF3) {
		this.tempF3 = tempF3;
	}
	public String getTempF4() {
		return tempF4;
	}
	public void setTempF4(String tempF4) {
		this.tempF4 = tempF4;
	}
}

好了，万事俱备，只欠东风，下面我们利用gson包提供的Gson类的parseJson和fromJson方法来实现解析和反解析：

public class Main2 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		String json = getJSONString();
		Gson gson = new Gson();
		WeatherStation ws = gson.fromJson(json, WeatherStation.class);
		System.out.println(ws.getWeatherinfo().getCity());
		System.out.println(ws.getWeatherinfo().getCity_en());
		System.out.println(ws.getWeatherinfo().getTempF3());
		System.out.println(ws.getWeatherinfo().getTempF4());
	}
	
	private static String getJSONString()   {
		try {
			URL url = new URL("http://m.weather.com.cn/data/101210101.html");
			HttpURLConnection conn = (HttpURLConnection)url.openConnection();
			InputStream is = conn.getInputStream();
			BufferedReader br = new BufferedReader(new InputStreamReader(is,"utf-8"));
			String msg = null;
			StringBuilder sb = new StringBuilder();
			while((msg = br.readLine()) != null) {
				sb.append(msg);
			}
			return sb.toString();
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}
	}
}

看看输出：

杭州
hangzhou
42.8℉~35.6℉
50℉~37.4℉

import java.io.IOException;

import com.google.gson.Gson;

public class Main {


	public static void main(String[] args) throws IOException {

		Disney sh = new Disney();
		sh.setName("shanghai disney");
		sh.setLocation(new Location("shanghai Rd.", 123456));
		Disney ny = new Disney();
		ny.setName("NewYork disney");
		ny.setLocation(new Location("newyork Rd.", 54321));
		
		Disney[] disneys = {sh,ny};
		Gson gson = new Gson();
		String jsonString = gson.toJson(disneys);
		System.out.println(jsonString);
		
		Disney[] disneyss = gson.fromJson(jsonString, Disney[].class);

		for(Disney disney : disneyss) {
			System.out.println(disney.getName());
			System.out.println(disney.getSingleTicket());
			for(String interest : disney.getIntrests()) {
				System.out.println(interest);
			}
			System.out.println(disney.getLocation().getStreet());
		}
	}

}

class Location {
	private String street;
	private long postcode;
	
	public Location(String street,long postcode) {
		this.street = street;
		this.postcode = postcode;
	}
	
	public String getStreet() {
		return street;
	}
	public void setStreet(String street) {
		this.street = street;
	}
	public long getPostcode() {
		return postcode;
	}
	public void setPostcode(long postcode) {
		this.postcode = postcode;
	}
	
	
}
class Disney {
	
	private String name;
	private Location location;
	private double singleTicket = 8.8;
	private String[] intrests = {"boat","water","sky"};
	
	public String[] getIntrests() {
		return intrests;
	}

	public void setIntrests(String[] intrests) {
		this.intrests = intrests;
	}

	public Disney() {
		
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Location getLocation() {
		return location;
	}

	public void setLocation(Location location) {
		this.location = location;
	}

	public double getSingleTicket() {
		return singleTicket;
	}

	public void setSingleTicket(double singleTicket) {
		this.singleTicket = singleTicket;
	}

	@Override
	public String toString() {
		return "Disney [name=" + name + ", location=" + location
				+ ", singleTicket=" + singleTicket + "]";
	}

	
	
}