JSON 之FastJson解析

一、Fastjson API入口类是com.alibaba.fastjson.JSON，常用的序列化操作都可以在JSON类上的静态方法直接完成。

public static final Object parse(String text); // 把JSON文本parse为JSONObject或者JSONArray 
public static final JSONObject parseObject(String text)； // 把JSON文本parse成JSONObject    
public static final T parseObject(String text, Class clazz); // 把JSON文本parse为JavaBean 
public static final JSONArray parseArray(String text); // 把JSON文本parse成JSONArray 
public static final List parseArray(String text, Class clazz); //把JSON文本parse成JavaBean集合 
public static final String toJSONString(Object object); // 将JavaBean序列化为JSON文本 
public static final String toJSONString(Object object, boolean prettyFormat); // 将JavaBean序列化为带格式的JSON文本 
public static final Object toJSON(Object javaObject); 将JavaBean转换为JSONObject或者JSONArray。

二、FastJson解析JSON步骤
   A、服务器端将数据转换成json字符串

     首先、服务器端项目要导入阿里巴巴的fastjson的jar包至builtPath路径下（这些可以到fastjson官网下载：http://code.alibabatech.com/wiki/display/FastJSON/Home-zh）

然后将数据转为json字符串，核心函数是：
public static String createJsonString(Object value)
   {
      String alibabaJson = JSON.toJSONString(value);
      return alibabaJson;
   }
B、客户端将json字符串转换为相应的javaBean
 首先客户端也要导入fastjson的两个jar包
1、客户端获取json字符串
public class HttpUtil
{
   
   public static String getJsonContent(String urlStr)
   {
      try
      {// 获取HttpURLConnection连接对象
         URL url = new URL(urlStr);
         HttpURLConnection httpConn = (HttpURLConnection) url
               .openConnection();
         // 设置连接属性
         httpConn.setConnectTimeout(3000);
         httpConn.setDoInput(true);
         httpConn.setRequestMethod("GET");
         // 获取相应码
         int respCode = httpConn.getResponseCode();
         if (respCode == 200)
         {
            return ConvertStream2Json(httpConn.getInputStream());
         }
      }
      catch (MalformedURLException e)
      {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }
      catch (IOException e)
      {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }
      return "";
   }

   
   private static String ConvertStream2Json(InputStream inputStream)
   {
      String jsonStr = "";
      // ByteArrayOutputStream相当于内存输出流
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      byte[] buffer = new byte[1024];
      int len = 0;
      // 将输入流转移到内存输出流中
      try
      {
         while ((len = inputStream.read(buffer, 0, buffer.length)) != -1)
         {
            out.write(buffer, 0, len);
         }
         // 将内存流转换为字符串
         jsonStr = new String(out.toByteArray());
      }
      catch (IOException e)
      {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }
      return jsonStr;
   }
}
2、使用泛型获取javaBean（核心函数）
   public static T getPerson(String jsonString, Class cls) {
      T t = null;
      try {
         t = JSON.parseObject(jsonString, cls);
      } catch (Exception e) {
         // TODO: handle exception
      }
      return t;
   }
public static List getPersons(String jsonString, Class cls) {
      List list = new ArrayList();
      try {
         list = JSON.parseArray(jsonString, cls);
      } catch (Exception e) {
      }
      return list;
   }
public static List> listKeyMaps(String jsonString) {
      List> list = new ArrayList>();
      try {
         list = JSON.parseObject(jsonString,
               new TypeReference>>() {
         });
      } catch (Exception e) {
         // TODO: handle exception
      }
      return list;
   }