使用GSON获取天气预报信息

gson可能大部分程序员都不熟悉，简言之就是一个json工具，可实现对象和json字符串之间的转换；有人可能会说了用json-lib就可以了啊，之前我也是用json-lib的但是总是觉得很麻烦，生成json还OK但是解析就要费九牛二虎之力了，权衡之下还是选择使用gson.这次就使用gson配合百度API来实现天气预报的查询功能。

一  gson的下载地址

Gson是Google提供的用于在Java对象和JSON字符串之间进行转换的Java类库。

下载地址1：https://code.google.com/p/google-gson/downloads/list
下载地址2：http://download.csdn.net/detail/lyq8479/8451103

二  代码实现

1 先来体验下gson的简单使用

先搞个pojo类：

package org.lxh;public class UserInfo {private String name;private String address;private String email;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}}

接下来直接上测试类：

package org.lxh;import java.util.ArrayList;import java.util.List;import com.google.gson.Gson;import com.google.gson.reflect.TypeToken;public class UseGson {  public static void main(String args[]){    UserInfo u1=new UserInfo();  u1.setAddress("上海浦东新区");  u1.setEmail("[e-mail]");  u1.setName("王大锤");    Gson gson=new Gson();  String jsonStr=gson.toJson(u1);    System.out.println(jsonStr);     UserInfo u2=new UserInfo();  u2.setAddress("安徽芜湖");  u2.setEmail("[e-mail]");  u2.setName("蜡笔小新");    List<UserInfo> all=new ArrayList<UserInfo>();  all.add(u1);  all.add(u2);    String jsonArrStr=gson.toJson(all);    System.out.println("------------------生成json数组-------------------");  System.out.println(jsonArrStr);  System.out.println("------------------把JSON转成对象-------------------");  List<UserInfo> obj=gson.fromJson(jsonArrStr, new TypeToken<List<UserInfo>>(){}.getType());  System.out.println(obj.get(0).getAddress());    }}

来看下运行效果：

2  封装天气预报工具类

百度API地址：http://developer.baidu.com/map/index.php?title=car/api/weather

使用之前要先注册个开发者账号，之后创建应用就能得到ak了，这些操作就自己搞了，你们都懂的。

（1）封装WeatherData类

 

package org.lxh;public class WeatherData {private String date;private String weather;private String dayPictureUrl;private String nightPictureUrl;private String wind;private String temperature;public String getDate() {return date;}public void setDate(String date) {this.date = date;}public String getDayPictureUrl() {return dayPictureUrl;}public void setDayPictureUrl(String dayPictureUrl) {this.dayPictureUrl = dayPictureUrl;}public String getNightPictureUrl() {return nightPictureUrl;}public void setNightPictureUrl(String nightPictureUrl) {this.nightPictureUrl = nightPictureUrl;}public String getWind() {return wind;}public void setWind(String wind) {this.wind = wind;}public String getTemperature() {return temperature;}public void setTemperature(String temperature) {this.temperature = temperature;}public String getWeather() {return weather;}public void setWeather(String weather) {this.weather = weather;}}

（2）封装WeatherResult

package org.lxh;import java.util.List;public class WeatherResult {private String currentCity;private String pm25;private List<WeatherData> weather_data;public String getCurrentCity() {return currentCity;}public void setCurrentCity(String currentCity) {this.currentCity = currentCity;}public String getPm25() {return pm25;}public void setPm25(String pm25) {this.pm25 = pm25;}public List<WeatherData> getWeather_data() {return weather_data;}public void setWeather_data(List<WeatherData> weatherData) {weather_data = weatherData;}}

（3）封装WeatherResp

 

package org.lxh;import java.util.List;public class WeatherResp {private int error;private String status;private String date;private List<WeatherResult> results;public int getError() {return error;}public void setError(int error) {this.error = error;}public String getStatus() {return status;}public void setStatus(String status) {this.status = status;}public String getDate() {return date;}public void setDate(String date) {this.date = date;}public List<WeatherResult> getResults() {return results;}public void setResults(List<WeatherResult> results) {this.results = results;}}

（4）HttpURLConnection操作工具类

package org.lxh;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.net.ConnectException;import java.net.HttpURLConnection;import java.net.URL;public class CommonUtil {  public static String httpRequest(String requestUrl, String requestMethod, String outputStr) {                 StringBuffer buffer = new StringBuffer();          try {               URL url = new URL(requestUrl);              HttpURLConnection httpUrlConn = (HttpURLConnection) url.openConnection();              httpUrlConn.setDoOutput(true);              httpUrlConn.setDoInput(true);              httpUrlConn.setUseCaches(false);              // 设置请求方式（GET/POST）              httpUrlConn.setRequestMethod(requestMethod);              httpUrlConn.connect();                         // 当有数据需要提交时              if (null != outputStr) {                  OutputStream outputStream = httpUrlConn.getOutputStream();                  // 注意编码格式，防止中文乱码                  outputStream.write(outputStr.getBytes("UTF-8"));                  outputStream.close();              }                // 将返回的输入流转换成字符串              InputStream inputStream = httpUrlConn.getInputStream();              InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "utf-8");              BufferedReader bufferedReader = new BufferedReader(inputStreamReader);                String str = null;              while ((str = bufferedReader.readLine()) != null) {                  buffer.append(str);              }              bufferedReader.close();              inputStreamReader.close();              // 释放资源              inputStream.close();              inputStream = null;                     } catch (ConnectException ce) {          ce.printStackTrace();                  } catch (Exception e) {                    e.printStackTrace();        }          return buffer.toString();      }  }

（5）天气预报获取工具类

package org.lxh;import java.net.URLEncoder;import java.util.Iterator;import java.util.List;import com.google.gson.Gson;public class WeatherUtil {   public static String getWeatherResult(String cityName) throws Exception{      String requestUrl="http://api.map.baidu.com/telematics/v3/weather?location={LOCATION}&output=json&ak={KEY}";   String requestWeatherUrl=requestUrl.replace("{LOCATION}", URLEncoder.encode(cityName, "UTF-8")).replace("{KEY}", "你的AK");      String result=CommonUtil.httpRequest(requestWeatherUrl, "POST", null);   //System.out.println(result);   Gson gson=new Gson();   WeatherResp wresp=gson.fromJson(result, WeatherResp.class);      StringBuffer buf=new StringBuffer();   buf.append(cityName+"天气预报"+"\n\n");      List<WeatherData> wdata=wresp.getResults().get(0).getWeather_data();   Iterator<WeatherData> it=wdata.iterator();   while(it.hasNext()){   WeatherData w=it.next();   buf.append(w.getDate()+","+w.getWeather()+","+w.getTemperature()+","+w.getWind());   buf.append("\n\n");   }   return buf.toString();   }      public static void main(String args[]) throws Exception{   System.out.println(getWeatherResult("苏州"));   }}

来看下运行效果截图：

天气预报的接口来源还是挺多的，数据交互方式也不尽相同，选择合适的就行，不一定局限于百度的API.gson的使用关键在于json数据的分析，按结构提取出合适的pojo类能很好的降低解析难度。