Java服務器非阻塞查詢

Question

我正在使用以下代碼從Android客戶端讀取一些數據。一切都很好。但是現在我被要求讓這個服務器代碼不被阻塞。有什麼建議嗎？我試圖使用線程，但不知道如何？我是初學者在Java中:)

感謝

import java.awt.image.BufferedImage; 
import java.io.BufferedOutputStream; 
import java.io.ByteArrayInputStream; 
import java.io.DataInputStream; 
import java.io.File; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.net.ServerSocket; 
import java.net.Socket; 
import java.util.Calendar; 
import java.util.Date; 

import javax.imageio.ImageIO; 


public class Server { 
    //Server Constructor 
    public Server() 
    {} 
    //Variables Initialization 
    private static ServerSocket server; 
    byte[] imagetemp; 
    private static Socket socket1; 
    private static boolean newImage; 
    private static Sdfdata data; 
    private static boolean cond; 
    public static int port; 
    private static int number = 0; 
    //Image Availability return method 
    public boolean imageAvailable() 
    { 
     return newImage; 
    } 
    public boolean clientchk() 
    { 
     return socket1.isClosed(); 
    } 
    //Image Flag set by Vis group when image read. 
    public void setImageFlag(boolean set) 
    { 
     newImage = set; 
    } 
    // Send the data to the Vis Group 
    public Sdfdata getData() 
    { 
    return data; 
    } 
    //Starts the Server 
    public static boolean start(int port1) 
    { 
     try { 
      port=port1; 

       server = new ServerSocket(port1); 
      System.out.println("Waiting for Client to Connect"); 
      //New thread here 

      socket1=server.accept(); 


     } catch (IOException e) { 
      System.out.println("Cannot Connect"); 
      e.printStackTrace(); 
      return false; 
     } 
     return true; 
    } 
    //Stops the Server 
    public boolean stop() 
    { 

     try { 
      socket1.close(); 
     } 
     catch (IOException e) 
     { 

      e.printStackTrace(); 
      return false; 
     } 
     return true; 

    } 
    /** 
    * @param args 
    * @throws IOException 
    */ 



    public static void main(String[] args) throws IOException { 
     // Starts the server 
     start(4444); 
     // DataInput Stream for reading the data 
     DataInputStream in = null; 
     try { 
      in = new DataInputStream(socket1.getInputStream()); 
     } catch (IOException e1) { 
      // TODO Auto-generated catch block 
      e1.printStackTrace(); 
     } 
     cond=true; 

     do { 

      try 
      { 
       //Read Image Data 
       int length = in.readInt(); 
       //Create an ByteArray of length read from Client for Image transfer 
       Sdfdata data = new Sdfdata(length); 

       //for (int i=0; i<length; i++) 
       //{ data.image[i] = in.readbyte(); } 

       if (length > 0) { 
        in.readFully(data.image); 
       } 

       //Read Orientation 
       data.orientation[0] = in.readFloat();  //Orientation x 
       data.orientation[1] = in.readFloat();  //Orientation y 
       data.orientation[2] = in.readFloat();  //Orientation z 

       //Read GPS 
       data.longitude = in.readDouble(); 
       data.latitude = in.readDouble(); 
       data.altitude = in.readDouble(); 

       //Display orientation and GPS data 
       System.out.println(data.orientation[0] + " " + data.orientation[1] + " " + data.orientation[2]); 
       System.out.println(data.longitude + " " + data.latitude + " " + data.altitude); 

       String fileName = "IMG_" + Integer.toString(++number) + ".JPG"; 
       System.out.println("FileName: " + fileName); 
       FileOutputStream fos = new FileOutputStream(fileName); 
       fos.write(data.image); 
       fos.close(); 





       /*InputStream ins = new ByteArrayInputStream(data.image); 
       BufferedImage image = ImageIO.read(ins); 
       ImageIO.write(image, "JPG", new File (fileName)); 
       */ 
       //set image flag 
       newImage = true; 


      } catch (Exception e) { 
       //System.out.println("EOF Or ? " + e); 

       cond =false; 
       socket1.close(); 
       server.close(); 
       start(port); 

      } 
    }while (cond); 
     } 

}

Answer 1

你的代碼啓動服務器，等待連接，讀取從第一連接的客戶端的一些數據，然後寫這後退出數據到文件。要求讓您的服務器「非阻塞」可能意味着您被要求將其更改爲使用異步IO（可能不太可能），或者這可能意味着您被要求處理多個客戶端一次 - 因爲目前你只能服務一個客戶，然後你的程序退出。

這個問題很難回答，因爲你現在的代碼離你所需要的地方很遠，看起來好像有人在網絡，套接字和一般的Java編程上讀到這些是一個很好的開始。

我推薦使用Netty來處理Java中與網絡相關的任何事情，它們的樣本和文檔都很好且易於遵循。祝你好運！