
import java.io.DataOutputStream;
import java.io.ObjectInputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class sendToServer {
    
    String url_string = "";
    public void send(String json){
        URL url = null;
        HttpURLConnection connection = null;
        try {
            
            url = new URL(url_string);
            connection = (HttpURLConnection) url
                    .openConnection();
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setConnectTimeout(10000);
            connection.setReadTimeout(10000);
            connection.setRequestMethod("POST");// 设置为post方法
            
            // 输出流
            DataOutputStream outobj = new DataOutputStream(
                    connection.getOutputStream());
            
            Gson gson = new Gson();
            User user = new User();
            user.setId("aa");
            user.setClassmark("classmark");
            user.setEmail("aaa");
            user.setPassword("aaa");
            user.setPhone("111");
            String userson = gson.toJson(user);
            
            // 先写入标志服 在写 json 那么读的时候 先读取json 再读取标志
            outobj.writeInt(3);
            outobj.writeUTF(userson);

            outobj.flush();
            
            outobj.close();
            
            
            // 输入流 服务器传回来的东西
            ObjectInputStream ois = new ObjectInputStream(
                    connection.getInputStream());
            String result = (String) ois.readObject();
            ois.close();
            connection.disconnect();
            
        }catch(Exception e){
            
        }
    }

}

服务器发出反馈的代码

//反过来的代码 

            DataInputStream ios = null;
            ios = new DataInputStream(request.getInputStream());
            ObjectOutputStream oos = null;
            oos = new ObjectOutputStream(response.getOutputStream());       
            //读取标志符
            int i = ios.readInt();
            
            System.out.println(i);
            
            User user = new User();
            user.setId("hahaha");
            user.setPassword("1234");
            //user.setIdentity("1111");
            
            Gson gson = new Gson();
            String string = gson.toJson(user);
            
                
            //回传对象
            oos.writeObject(string);