Json数据处理:使用GSON处理数据的方法

1.简单Json数据处理

        使用普通的json解析方法即JsonObject和JsonArray的配合使用，这对于解析小数据的json数据还是比较实用，但是当解析json数据比较复杂的时候这种方法就显得比较吃力也比较麻烦了。

2.复杂Json数据处理

使用google开源的gson.jar包来解析。

如下面我们要解析的一个json数据：

String json = {"a":"100","b":[{"b1":"b_value1","b2":"b_value2"}, {"b1":"b_value1","b2":"b_value2"}]，"c": {"c1":"c_value1","c2":"c_value2"}} 

首先我们需要定义一个序列化的Bean，这里采用内部类的形式，看起来会比较清晰一些：

    public class JsonBean {                               public String a;                               public List<B> b;                               public C c;                                     public static class B {                                                  public String b1;                                              public String b2;                              }                                        public static class C {                                       public String c1;                                       public String c2;                             }                    }  

很多时候大家都是不知道这个Bean是该怎么定义，这里面需要注意几点：
             1、内部嵌套的类必须是static的，要不然解析会出错；
             2、类里面的属性名必须跟Json字段里面的Key是一模一样的；
             3、内部嵌套的用[]括起来的部分是一个List，所以定义为 public List<B> b，而只用{}嵌套的就定义为 public C c

          解析方法如下:

Gson gson = new Gson();  java.lang.reflect.Type type = new TypeToken<JsonBean>() {}.getType();  JsonBean jsonBean = gson.fromJson(json, type);

如果需要解析的Json嵌套了很多层，同样可以可以定义一个嵌套很多层内部类的Bean，需要细心的对照Json字段来定义.

解析复杂的json数据:

{    "error": 0,    "status": "success",    "date": "2014-05-10",    "results": [        {            "currentCity": "南京",            "weather_data": [                {                    "date": "周六(今天, 实时：19℃)",                    "dayPictureUrl": "http://api.map.baidu.com/images/weather/day/dayu.png",                    "nightPictureUrl": "http://api.map.baidu.com/images/weather/night/dayu.png",                    "weather": "大雨",                    "wind": "东南风5-6级",                    "temperature": "18℃"                },                {                    "date": "周日",                    "dayPictureUrl": "http://api.map.baidu.com/images/weather/day/zhenyu.png",                    "nightPictureUrl": "http://api.map.baidu.com/images/weather/night/duoyun.png",                    "weather": "阵雨转多云",                    "wind": "西北风4-5级",                    "temperature": "21 ~ 14℃"                }            ]        }    ]}

必须定义如下一些的javaBean数据

Status.java

public class Status   {          private String error;          private String status;          private String date;          private List<Results> results;          public String getError()           {              return error;          }          public void setError(String 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<Results> getResults()           {              return results;          }          public void setResults(List<Results> results)           {              this.results = results;          }          @Override          public String toString()           {              return "Status [error=" + error + ", status=" + status                      + ", date=" + date + ", results=" + results + "]";          }  

Results.java

    public class Results       {             private String currentCity;          private List<Weather> weather_data;          public String getCurrentCity()           {              return currentCity;          }          public void setCurrentCity(String currentCity)           {              this.currentCity = currentCity;          }          public List<Weather> getWeather_data()           {              return weather_data;          }          public void setWeather_data(List<Weather> weather_data)           {              this.weather_data = weather_data;          }          @Override          public String toString()           {              return "Results [currentCity=" + currentCity + ", weather_data="                      + weather_data + "]";          }  

Weather.java

public class Weather {      private String date;                  private String dayPictureUrl;                  private String nightPictureUrl;                  private String weather;                  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 getWeather() {                      return weather;                  }                  public void setWeather(String weather) {                      this.weather = weather;                  }                  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;                  }                  @Override                  public String toString() {                      return "Weather [date=" + date + ", dayPictureUrl="                              + dayPictureUrl + ", nightPictureUrl="                              + nightPictureUrl + ", weather=" + weather                              + ", wind=" + wind + ", temperature=" + temperature                              + "]";                  }   

解析数据类

    public class MainActivity extends Activity       {          private Button tojson;            RequestQueue mQueue;              StringRequest stringRequest;              Gson gson;          String str;                @Override          protected void onCreate(Bundle savedInstanceState)           {              super.onCreate(savedInstanceState);              setContentView(R.layout.activity_main);                            tojson = (Button)findViewById(R.id.tojson);              gson = new Gson();                mQueue = Volley.newRequestQueue(MainActivity.this);                //http://10.19.20.12/upgrade/test.txt是测试使用的json数据              stringRequest = new StringRequest("http://10.19.20.12/upgrade/test.txt",                      new Response.Listener<String>()                       {                          @Override                          public void onResponse(String response)                           {                              Log.d("TAG", response);                              System.out.println("response="+response);                              Status status = gson.fromJson(response, Status.class);                              System.out.println("status="+status);                              System.out.println("-------------------------------------");                              List<Results> result = status.getResults();                              System.out.println("result="+result);                                                        }                      },                       new Response.ErrorListener()                       {                          @Override                          public void onErrorResponse(VolleyError error)                           {                              Log.e("TAG", error.getMessage(), error);                          }                            });                      tojson.setOnClickListener(new OnClickListener()               {                         @Override                  public void onClick(View v)                   {                      mQueue.add(stringRequest);                  }              });               }                             }  

其中上面的RequestQueue是开源网络库Volley的使用。