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”:19
         }    

2、数组类型（有序列表）

 {
        “students”:
        [
            {“name”:”Alice”,“age”:19},
            {“name”:”Ben”,”age”:11}
        ]
     }

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=0;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:10,address:山东
第1个对象name:小李,age:15,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=0;i<p.length();i++)
        {
            JSONObject person = p.getJSONObject(i);
            String name = person.getString("name");
            String image = person.getString("image");
            System.out.println("第"+(i+1)+"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=0;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:100
school:北大,good:true,className:化学系,classCount:45

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=0;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:1
name:小红,id:5
name:小王,id:7

 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);
        }

    }

}

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(5000);
        conn.setDoInput(true);
        InputStream in = null;
        if(conn.getResponseCode()==200)
        {
            in = conn.getInputStream();
            return changeToString(in);
        }
        return null;
    }

    private static String changeToString(InputStream in) throws IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] arr = new byte[1024];
        int len = 0;
        while((len = in.read(arr))!=-1)
        {
                        //写入内存流
            bos.write(arr,0,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
        
    }
 
}