https://my.oschina.net/yushulx/blog/298140
How to Implement a Java WebSocket Server for Image Transmission with Jetty
创建一个从WebSocketHandler继承的类WSHandler：
import org.eclipse.jetty.websocket.api.Session;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
import org.eclipse.jetty.websocket.api.annotations.WebSocket;
import org.eclipse.jetty.websocket.server.WebSocketHandler;
import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
@WebSocket
public class WSHandler extends WebSocketHandler {
@OnWebSocketClose
public void onClose(int statusCode, String reason) {
}
@OnWebSocketError
public void onError(Throwable t) {
}
@OnWebSocketConnect
public void onConnect(Session session) {
}
@OnWebSocketMessage
public void onMessage(String message) {
}
@Override
public void configure(WebSocketServletFactory factory) {
// TODO Auto-generated method stub
factory.register(WSHandler.class);
}
}设置一个端口和Handler，启动Server：
public static void main(String[] args) throws Exception {
Server server = new Server(2014);
server.setHandler(new WSHandler());
server.setStopTimeout(0);
server.start();
server.join();
}JavaScript客户端
写一个简单的测试。
Index.htm:
<!DOCTYPE html>
<html>
<body>
<script src="websocket.js"></script>
</body>
</html>Websocket.js:
var ws = new WebSocket("ws://127.0.0.1:2014/");
ws.onopen = function() {
alert("Opened");
ws.send("I'm client");
};
ws.onmessage = function (evt) {
};
ws.onclose = function() {
alert("Closed");
};
ws.onerror = function(err) {
alert("Error: " + err);
};图像传输
功能：
从网页中主动获取图像
服务端推送图像到网页中
代码修改
从网页中获取服务端数据。
在index.htm中添加一个按钮元素和一个图片元素：
<!DOCTYPE html>
<html>
<body>
<h1>WebSocket Image Display</h1>
<input type="button" id="button" value="image" ><br>
<img id="image"></<img>
<script src="websocket.js"></script>
</body>
</html>在Websocket.js中添加下面的代码：
ws.binaryType = "arraybuffer";
var button = document.getElementById("button");
button.onclick = function() {
ws.send("image"); // send the fetch request
};
ws.onmessage = function (evt) { // display the image
var bytes = new Uint8Array(evt.data);
var data = "";
var len = bytes.byteLength;
for (var i = 0; i < len; ++i) {
data += String.fromCharCode(bytes[i]);
}
var img = document.getElementById("image");
img.src = "data:image/png;base64,"+window.btoa(data);
};服务端收到消息之后，发送图片：
public void onMessage(String message) {
System.out.println("Message: " + message);
if (message.equals("image")) {
System.out.println("session: " + mSession);
if (mSession != null) {
try {
File f = new File("image\\github.jpg");
BufferedImage bi = ImageIO.read(f);
ByteArrayOutputStream out = new ByteArrayOutputStream();
ImageIO.write(bi, "png", out);
ByteBuffer byteBuffer = ByteBuffer.wrap(out.toByteArray());
mSession.getRemote().sendBytes(byteBuffer);
out.close();
byteBuffer.clear();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}从服务端发送数据到客户端。
在服务端的UI上添加两个按钮，一个用来加载本地图片，一个用来发送图片：
package com.ui;
import java.awt.BorderLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.filechooser.FileNameExtensionFilter;
import com.server.WSHandler;
import com.server.WebSocketServer;
public class UIMain extends JPanel
implements ActionListener {
private JButton mLoad, mSend;
private JFileChooser mFileChooser;
private JLabel mImage;
private byte[] mData;
private WebSocketServer mWebSocketServer;
public UIMain() {
super(new BorderLayout());
//Create a file chooser
mFileChooser = new JFileChooser();
FileNameExtensionFilter filter = new FileNameExtensionFilter(
".png.jpg", "png","jpg");
mFileChooser.setFileFilter(filter);
mLoad = new JButton("Load");
mLoad.addActionListener(this);
mSend = new JButton("Send");
mSend.addActionListener(this);
mSend.setEnabled(false);
// button panel
JPanel buttonPanel = new JPanel();
buttonPanel.add(mLoad);
buttonPanel.add(mSend);
add(buttonPanel, BorderLayout.PAGE_START);
// image panel
JPanel imageViewer = new JPanel();
mImage = new JLabel();
mImage.setSize(480, 640);
imageViewer.add(mImage);
add(imageViewer, BorderLayout.CENTER);
// WebSocketServer
mWebSocketServer = new WebSocketServer();
mWebSocketServer.start();
}
@Override
public void actionPerformed(ActionEvent e) {
}
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("WebSocket Demo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Add content to the window.
frame.add(new UIMain());
//Display the window.
frame.pack();
frame.setVisible(true);
frame.setResizable(false);
frame.setSize(480, 700);
double width = Toolkit.getDefaultToolkit().getScreenSize().getWidth();
double height = Toolkit.getDefaultToolkit().getScreenSize().getHeight();
int frameWidth = frame.getWidth();
int frameHeight = frame.getHeight();
frame.setLocation((int)(width - frameWidth) / 2, (int)(height - frameHeight) / 2);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
UIManager.put("swing.boldMetal", Boolean.FALSE);
createAndShowGUI();
}
});
}
}为了防止UI阻塞，Websocket server需要在线程中创建：
package com.server;
import org.eclipse.jetty.server.Server;
public class WebSocketServer extends Thread{
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
try {
Server server = new Server(2014);
server.setHandler(new WSHandler());
server.setStopTimeout(0);
server.start();
server.join();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}在按钮事件中添加图片添加和发送功能：
public void sendImage(byte[] data) {
if (mSession == null)
return;
try {
ByteBuffer byteBuffer = ByteBuffer.wrap(data);
mSession.getRemote().sendBytes(byteBuffer);
byteBuffer.clear();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == mLoad) {
int returnVal = mFileChooser.showOpenDialog(UIMain.this);
if (returnVal == JFileChooser.APPROVE_OPTION) {
File file = mFileChooser.getSelectedFile();
// load image data to byte array
try {
BufferedImage bi = ImageIO.read(file);
ByteArrayOutputStream out = new ByteArrayOutputStream();
ImageIO.write(bi, "png", out);
mData = out.toByteArray();
out.close();
} catch (IOException exception) {
exception.printStackTrace();
}
mImage.setIcon(new ImageIcon(mData));
mSend.setEnabled(true);
}
}
else if (e.getSource() == mSend) {
ArrayList<WSHandler> sessions = WSHandler.getAllSessions();
for (WSHandler session : sessions) {
session.sendImage(mData);
}
mSend.setEnabled(false);
}
}