JSON与GSON

JSON数据结构(可读性较差)
1.对象结构{"name":"value","nam":"val"}
2.数组结构[e1,e2,e3]["a","b","c"]
 
 
 <name>tomg</name> xml格式
 {"name":"tom"} json格式
 
 <student id="10086">
  <name>tom</name>
  <age>12</age>
  <gender>男</gender>
 </student>
 
 {"id":10086,"name":"tom","age":12,"gender":"男"}
 
 
 <class>
<student id="10000">xin</student>
<student id="100001">lai</student>
<student id="100002">feng</student>
<worker id="100003">li</worker>
<worker id="100004">guo</worker>
</class>


[{"id":10086,"name":"xin"},{"id":10010,"name":"lai"},{"id":10000,"name":"feng"}]
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JSON解析
org.json
JSONObject
JSONArray

gson：将数据解析成一个对象，然后将对象写出来就OK了

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使用框架进行解析：底层代码原理
package man;


import java.lang.reflect.Field;


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


public class JSON {
//将json字符串转化成class对象
public static <T> T fromJSON(String json,Class<T> c){
T t=null;
try {
t=c.newInstance();//InstantiationException - 如果此 Class 表示一个抽象类、接口、数组类、基本类型或 void； 或者该类没有 null 构造方法； 
//或者由于其他某种原因导致实例化失败。

JSONObject obj=new JSONObject(json);
Field[]field=c.getDeclaredFields();
for (Field f : field) {
String name=f.getName();
Object o=obj.get(name);
f.setAccessible(true);
f.set(t, o);
}
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

return t;
}
//将对象转化成json字符串
public static String toJSON(Object obj){
JSONObject o=new JSONObject();

//String json="";
//获取obj的class对象
Class<?>cla=obj.getClass();
//获取所有的属性
Field[]field=cla.getDeclaredFields();
for (Field f : field) {
String name=f.getName();
System.out.println(f.getName());
f.setAccessible(true);
try {
Object val=f.get(obj);
o.put(name, val);
} catch (IllegalArgumentException | IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
return o.toString();
}
}

--------------------------------------------------------------

Test测试类

public class Test {


public static void main(String[] args) {
// TODO Auto-generated method stub
Student stu1=new Student(43536, "jim", "IOS", "男", 56);


//JSON j=new JSON();
String man=JSON.toJSON(stu1);
System.out.println(man);

String json="{\"id\":685324,\"denger\":\"男\",\"age\":99,\"classname\":\"android\",\"name\":\"liebao\"}";
// Student stu2=null;
Student stu2=JSON.fromJSON(man, Student.class);//构造方法Student要有无参的，不然会出现错误java.lang.InstantiationException
//导错类也会出现相同错误
System.out.println(stu2);

}


}

后面还需加一个Student类，需要一个无参的构造方法

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json解析：

package jsonfile;


import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;


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


public class Test1 {


public static void main(String[] args) {
// TODO Auto-generated method stub
String json="";
try {
BufferedReader br=new BufferedReader(new FileReader("xin\\GetFeeds.txt"));
json=br.readLine();
br.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
JSONObject obj=new JSONObject(json);
JSONArray ary=obj.getJSONObject("paramz").getJSONArray("feeds");
for(int i=0;i<ary.length();i++){
String subject=ary.getJSONObject(i).getJSONObject("data").getString("subject");
System.out.println(subject);
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}


}


}

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json解析2：使用fileinputstream解析

package jsonfile;




import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;


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


public class Test {


public static void main(String[] args) {
// TODO Auto-generated method stub
readfile();
}
public static void readfile(){
try {
FileInputStream fis=new FileInputStream("xin\\GetFeeds.txt");
int r;
StringBuffer str=new StringBuffer();
byte[]b=new byte[1024];
while(-1!=(r=fis.read(b))){
//System.out.println(fis.read(b,0,r));不能将这句话输进来，不然会出现读到的str不完整
String st=new String(b, 0, r);
str.append(st);
}
fis.close();
String msg=str.toString();//要将StringBuffer转化回String才行，不然json会报错，提示找不到内容
System.out.println(str);
JSONObject  obj=new JSONObject(msg);
System.out.println(obj.getString("status"));
JSONObject obj1=obj.getJSONObject("paramz");
JSONArray array=obj1.getJSONArray("feeds");
for(int i=0;i<array.length();i++){
if(i<array.length()-4){
//System.out.println("进入到第"+(i+1)+"条新闻");
JSONObject obj2=array.getJSONObject(i);
JSONObject obj3=obj2.getJSONObject("data");
String subject=obj3.getString("subject");
System.out.println(subject);
}else{

}
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}


}

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gson解析网页数据：

package netJson;


import java.io.IOException;


import javax.xml.ws.Response;


import com.google.gson.Gson;


import okhttp3.OkHttpClient;
import okhttp3.Request;


public class GetTicket {


public static void main(String[] args) {
// TODO Auto-generated method stub
String url="http://piao.163.com/m/movie/list.html?app_id=2&mobileType=iPhone&ver=2.5&channel=lede&deviceId=C1985DD9-0125-4AB5-B66B-B91A85824BBA&apiVer=11&city=110000";
String json=getJSON(url);
//System.out.println(json);

Root root=new Gson().fromJson(json, Root.class);
//System.out.println(root.getRetdesc());
for(Film f:root.getList()){
System.out.println(f.getName()+"--"+f.getActors());
}
}


public static String getJSON(String url){
String json=null;
OkHttpClient client=new OkHttpClient();
Request request=new Request.Builder().url(url).build();
try {
okhttp3.Response response=client.newCall(request).execute();
if(response.isSuccessful()){
json=response.body().string();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return json;
}
}

从最外边的那个类一层层拨开，达到最后一个，这个视情况而定