Java数据解析---JSON

一、Java数据解析分为：XML解析和JSON解析

XML解析即是对XML文件中的数据解析，而JSON解析即对规定形式的数据解析,比XML解析更加方便

JSON解析基于两种结构：

1、键值对类型

          {
             “name”:”Alice”,
             “age”:
          }    

2、数组类型（有序列表）

  {
         “students”:
         [
             {“name”:”Alice”,“age”:},
             {“name”:”Ben”,”age”:}
         ]
      }

JSON解析依赖于外部jar包。

首先、服务器端项目要导入json的jar包和json所依赖的jar包至builtPath路径下（这些可以到JSON-lib官网下载：http://json-lib.sourceforge.net/）

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二、JSON解析字符串

1、先看一个最简单的字符串数据

 String json = "{name:'Alice',age:19,sex:'gril'}";

例如，对于这样一个字符串数据进行JSON解析，要解析的数据即是冒号（:）后面的数据 Alice 19 gril

把{}包含的所有看作是一个对象，把[]包含的看作为一个数组，分清JSONObject 和JSONArray 多练习 就掌握了

 package demo;

 import org.json.JSONException;
 import org.json.JSONObject;

 public class Demo01 {
     public static void main(String[] args) throws JSONException {
         String json = "{name:'Alice',age:19,sex:'gril'}";
         //将{}里面的整体看作一个对象
         JSONObject obj = new JSONObject(json);
         //根据键名（:前面的）获得值（：后面的）
         String name = obj.getString("name");
         int age = obj.getInt("age");
         String sex = obj.getString("sex");

         System.out.println("name:"+name+",age:"+age+",sex:"+sex);
     }
 }

2、再看一个对象中含对象的

         String json = "{student:{name:'Lucy',age:19,sex:'gril'}}";

 package demo;

 import org.json.JSONException;
 import org.json.JSONObject;

 public class Demo01 {

     public static void main(String[] args) throws JSONException {
         String json = "{student:{name:'Lucy',age:19,sex:'gril'}}";
         JSONObject obj = new JSONObject(json);
         //注意点
         JSONObject stu =obj.getJSONObject("student");
         String name = stu.getString("name");
         int age = stu.getInt("age");
         String sex = stu.getString("sex");

         System.out.println("name:"+name+",age:"+age+",sex:"+sex);
     }
 }

3、再看字符串中含有数组类型的情况

 String json = "{students:[{address:'山东',age:10,name:'小明'},{address:'河南',age:15,name:'小李'}]}";

 package json;

 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;

 public class Demo03 {
     public static void main(String[] args) throws JSONException {
         String json = "{students:[{address:'山东',age:10,name:'小明'},{address:'河南',age:15,name:'小李'}]}";
         JSONObject obj = new JSONObject(json);
         JSONArray stu = obj.getJSONArray("students");
         for(int i=;i<stu.length();i++)
         {
             JSONObject s = stu.getJSONObject(i);
             String name = s.getString("name");
             int age = s.getInt("age");
             String address = s.getString("address");

             System.out.println("第"+i+"个对象"+"name:"+name+",age:"+age+",address:"+address);

         }
     }
 }

 第0个对象name:小明,age:,address:山东
 第1个对象name:小李,age:,address:河南

4、看几个发杂点的字符串JSON解析

         String json = "{object:{persons:[{name:'小明',image:'帅'},{name:'小李',image:'高'},{name:'小王',image:'富'}]}}";

 package json;

 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;

 public class Demo04 {
     public static void main(String[] args) throws JSONException {
         String json = "{object:{persons:[{name:'小明',image:'帅'},{name:'小李',image:'高'},{name:'小王',image:'富'}]}}";
         JSONObject obj = new JSONObject(json);
         JSONObject object = obj.getJSONObject("object");
 //        JSONObject person = object.getJSONObject("persons");
         JSONArray p = object.getJSONArray("persons");
         for(int i=;i<p.length();i++)
         {
             JSONObject person = p.getJSONObject(i);
             String name = person.getString("name");
             String image = person.getString("image");
             System.out.println("第"+(i+)+"个对象的name:"+name+",image:"+image);
         }

     }
 }

 第1个对象的name:小明,image:帅
 第2个对象的name:小李,image:高
 第3个对象的name:小王,image:富

5、

         String json = "[{school:'清华',good:'false',class:{name:'物理系',count:100}},{school:'北大',good:'true',class:{name:'化学系',count:45}}]";

 package json;

 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;

 public class Demo05 {
     public static void main(String[] args) throws JSONException {
         String json = "[{school:'清华',good:'false',class:{name:'物理系',count:100}},{school:'北大',good:'true',class:{name:'化学系',count:45}}]";
         JSONArray arr = new JSONArray(json);
         for(int i=;i<arr.length();i++)
         {
             JSONObject ss = arr.getJSONObject(i);
             String school = ss.getString("school");
             String good = ss.getString("good");
             JSONObject clas = ss.getJSONObject("class");
             String name = clas.getString("name");
             String count = clas.getString("count");
             System.out.println("school:"+school+",good:"+good+",className:"+name+",classCount:"+count);
         }
     }
 }

 school:清华,good:false,className:物理系,classCount:
 school:北大,good:true,className:化学系,classCount:

6、

         String json ="{status:2,result:[{name:'小明',id:1}, {name:'小红',id:5},{name:'小王',id:7}]} " ;

 package json;

 import javax.naming.spi.DirStateFactory.Result;

 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;

 public class Demo06 {
     public static void main(String[] args) throws JSONException {
         String json ="{status:2,result:[{name:'小明',id:1}, {name:'小红',id:5},{name:'小王',id:7}]} " ;
         JSONObject obj = new JSONObject(json);
         String status = obj.getString("status");
         JSONArray result = obj.getJSONArray("result");
         for(int i=;i<result.length();i++)
         {
             JSONObject com = result.getJSONObject(i);
             String name = com.getString("name");
             String id = com.getString("id");
             System.out.println("name:"+name+",id:"+id);

         }

     }
 }

 name:小明,id:
 name:小红,id:
 name:小王,id:

三、解析网络中的数据

步骤：

1、得到指定网络地址上的数据的输入流，并存储到内存流

2、将内存流中的数据转换成字符串

3、对字符串进行JSON解析，并将数据存入到集合中

 import java.io.IOException;
 import java.util.List;

 import org.json.JSONException;

 public class Test {

     public static void main(String[] args) throws IOException, JSONException {
         String path = "http://..."; //数据源

         //得到json字符串
         String jsonString = HttpUtil.getJsonString(path);
         //把json字符串数据解析成集合
         List<T> list = HttpUtil.jsonParser(jsonString);
         //遍历集合
         for(T t:list)
         {
             System.out.println(t);
         }

     }

 }

主类

 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.List;

 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;

 public class HttpUtil {

     //得到服务器端的json字符串
     public static String getJsonString(String path) throws IOException
     {
         URL url = new URL(path);
         HttpURLConnection conn = (HttpURLConnection) url.openConnection();

         conn.setRequestMethod("GET");
         conn.setConnectTimeout();
         conn.setDoInput(true);
         InputStream in = null;
         if(conn.getResponseCode()==)
         {
             in = conn.getInputStream();
             return changeToString(in);
         }
         return null;
     }

     private static String changeToString(InputStream in) throws IOException {
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         byte[] arr = new byte[];
         int len = ;
         while((len = in.read(arr))!=-)
         {
                         //写入内存流
             bos.write(arr,,len);
         }
                 //转换成字符串形式返回
         return new String(bos.toByteArray(),"utf-8");
     }

     //解析json字符串，
     public static List<T> jsonParser(String jsonString) throws JSONException
     {
         List<T> list = new ArrayList<T>();
         JSONObject obj = new JSONObject(jsonString);
         //依据实际情况进行JSON解析
         return list; //多个人的信息

     }

 }

解析类