java - 在java中使用带有服务器的html5客户端

Question

HTML5 客户端通过在 html5 websocket 客户端中提供客户端来减少程序员的工作量。学习如何在 java 中将这个 html5 websocket 客户端与服务器一起使用对许多程序员来说都是有益的。

我想创建一个与 java 服务器通信的HTML5 客户端示例，但我无法找到如何做到这一点的方法。任何人都可以点亮它吗？

参考：使用 c++ 演示 html5 客户端/服务器

我在http://java.dzone.com/articles/creating-websocket-chat上找到了一个演示，但它对我不起作用..

Answer 1

我已经实现了一个简单的java 服务器端示例，我们可以看看。我首先创建一个 ServerSocket，它侦听端口 2005 上的连接

public class WebsocketServer {

public static final int MASK_SIZE = 4;
public static final int SINGLE_FRAME_UNMASKED = 0x81;
private ServerSocket serverSocket;
private Socket socket;

public WebsocketServer() throws IOException {
    serverSocket = new ServerSocket(2005);
    connect();
}

private void connect() throws IOException {
    System.out.println("Listening");
    socket = serverSocket.accept();
    System.out.println("Got connection");
    if(handshake()) {
         listenerThread();
    }
}

正如RFC 标准中定义的 websocket 协议，当客户端通过 websocket 连接时，必须进行握手。因此，让我们看一下 handshake() 方法，它非常丑陋，因此将逐步完成：第一部分读取客户端握手。

private boolean handshake() throws IOException {
    PrintWriter out = new PrintWriter(socket.getOutputStream());
    BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

    //This hashmap will be used to store the information given to the server in the handshake
    HashMap<String, String> keys = new HashMap<>();
    String str;
    //Reading client handshake, handshake ends with CRLF which is again specified in the RFC, so we keep on reading until we hit ""...
    while (!(str = in.readLine()).equals("")) {
        //Split the string and store it in our hashmap
        String[] s = str.split(": ");
        System.out.println(str);
        if (s.length == 2) {
            keys.put(s[0], s[1]);
        }
    }

根据 RFC - 第 1.2 节，客户端握手看起来像这样（这是 chrome 给我的，版本 22.0.1229.94 m）！

GET / HTTP/1.1
Upgrade: websocket
Connection: Upgrade
Host: localhost:2005
Origin: null
Sec-WebSocket-Key: PyvrecP0EoFwVnHwC72ecA==
Sec-WebSocket-Version: 13
Sec-WebSocket-Extensions: x-webkit-deflate-frame

现在我们可以使用键映射在握手过程中创建相应的响应。引用 RFC：

为了证明握手被接收，服务器必须获取两条信息并将它们组合起来形成响应。第一条信息来自|Sec-WebSocket-Key| 客户端握手中的标头字段。对于此标头字段，服务器必须获取该值并将其与全局唯一标识符“258EAFA5-E914-47DA-95CA-C5AB0DC85B11”以字符串形式连接起来，不理解WebSocket 协议。然后在服务器的握手中返回此连接的 SHA-1 哈希（160 位），base64 编码。

所以这就是我们必须做的！将 Sec-WebSocket-Key 与魔术字符串连接，使用 SHA-1 哈希函数对其进行哈希处理，然后对其进行 Base64 编码。这就是下一个丑陋的单线所做的。

String hash;
try {
    hash = new BASE64Encoder().encode(MessageDigest.getInstance("SHA-1").digest((keys.get("Sec-WebSocket-Key") + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11").getBytes()));
} catch (NoSuchAlgorithmException ex) {
    ex.printStackTrace();
    return false;
}

然后，我们只需在“Sec-WebSocket-Accept”字段中创建新的哈希返回预期的响应。

    //Write handshake response
    out.write("HTTP/1.1 101 Switching Protocols\r\n"
            + "Upgrade: websocket\r\n"
            + "Connection: Upgrade\r\n"
            + "Sec-WebSocket-Accept: " + hash + "\r\n"
            + "\r\n");
    out.flush();

    return true;

}

我们现在已经成功地在客户端和服务器之间建立了 websocket 连接。所以现在怎么办？我们如何让他们互相交谈？我们可以从服务器向客户端发送消息开始。注意！从这一点开始，我们不再使用 HTTP 与客户端对话。现在我们必须通信发送纯字节，并解释传入的字节。那么我们该怎么做呢？

来自服务器的消息必须采用称为“帧”的特定格式，如 RFC - 5.6 节中所述。当从服务器发送消息时，RFC 声明第一个字节必须指定它是什么类型的帧。一个值为 0x81 的字节告诉客户端我们正在发送一条“单帧无屏蔽文本消息”，它基本上是 - 一条文本消息。后续字节必须表示消息的长度。紧随其后的是数据或有效负载。好吧，好吧......让我们实现它！

public void sendMessage(byte[] msg) throws IOException {
        System.out.println("Sending to client");
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        BufferedOutputStream os = new BufferedOutputStream(socket.getOutputStream());
        //first byte is kind of frame
        baos.write(SINGLE_FRAME_UNMASKED);

        //Next byte is length of payload
        baos.write(msg.length);

        //Then goes the message
        baos.write(msg);
        baos.flush();
        baos.close();
        //This function only prints the byte representation of the frame in hex to console
        convertAndPrint(baos.toByteArray());

        //Send the frame to the client
        os.write(baos.toByteArray(), 0, baos.size());
        os.flush();
}

因此，要向客户端发送消息，我们只需调用 sendMessage("Hello, client!".getBytes())。

那不是太难了吗？接收来自客户端的消息怎么样？好吧，它有点复杂，但坚持下去！

来自客户端的帧 sendt 的结构几乎与来自服务器的帧 sendt 的结构相同。第一个字节是消息类型，第二个字节是有效载荷长度。然后有一个区别：接下来的四个字节代表一个掩码。什么是掩码，为什么来自客户端的消息被屏蔽，而服务器消息却没有？从 RFC - 第 5.1 节，我们可以看到：

...客户端必须屏蔽它发送给服务器的所有帧...服务器不能屏蔽它发送给客户端的任何帧。

所以简单的答案是：我们必须这样做。那么为什么我们必须这样做，你可能会问？我不是告诉过你阅读 RFC 吗？

继续前进，在帧中的四字节掩码之后，被掩码的有效载荷紧随其后。还有一件事，客户端必须将帧中最左边的第 9 位设置为 1，以告诉服务器消息已被屏蔽（查看 RFC 中整洁的 ASCII-art 帧 - 第 5.2 节）。最左边的第 9 位对应于我们第二个字节中的最左边的位，但是嘿，那是我们的有效载荷长度字节！这意味着来自我们客户端的所有消息的有效负载长度字节等于 0b10000000 = 0x80 + 实际有效负载长度。因此，要找出真正的有效载荷长度，我们必须从有效载荷长度字节（帧中的第二个字节）中减去 0x80、128 或 0b10000000（或您可能喜欢的任何其他数字系统）。

哇，好吧..听起来很复杂...对于“TLDR”-伙计们，摘要：从第二个字节中减去 0x80 以获得有效负载长度...

public String reiceveMessage() throws IOException {
    //Read the first two bytes of the message, the frame type byte - and the payload length byte
    byte[] buf = readBytes(2);
    System.out.println("Headers:");
    //Print them in nice hex to console
    convertAndPrint(buf);
    //And it with 00001111 to get four lower bits only, which is the opcode
    int opcode = buf[0] & 0x0F;
    
    //Opcode 8 is close connection
    if (opcode == 8) {
        //Client want to close connection!
        System.out.println("Client closed!");
        socket.close();
        System.exit(0);
        return null;
    } 
    //Else I just assume it's a single framed text message (opcode 1)
    else {
        final int payloadSize = getSizeOfPayload(buf[1]);
        System.out.println("Payloadsize: " + payloadSize);

        //Read the mask, which is 4 bytes, and than the payload
        buf = readBytes(MASK_SIZE + payloadSize);
        System.out.println("Payload:");
        convertAndPrint(buf);
        //method continues below!

现在我们已经阅读了整个消息，是时候揭开它的面具了，这样我们就可以对有效负载有所了解了。为了取消屏蔽它，我创建了一个方法，该方法将屏蔽和有效负载作为参数，并返回解码后的有效负载。所以调用是通过以下方式完成的：

    buf = unMask(Arrays.copyOfRange(buf, 0, 4), Arrays.copyOfRange(buf, 4, buf.length));
    String message = new String(buf);
    return message;
    }
}

现在的 unMask 方法相当甜蜜和微小

private byte[] unMask(byte[] mask, byte[] data) {
        for (int i = 0; i < data.length; i++) {
              data[i] = (byte) (data[i] ^ mask[i % mask.length]);
        }
        return data;
}

getSizeOfPayload 也是如此：

private int getSizeOfPayload(byte b) {
    //Must subtract 0x80 from (unsigned) masked frames
    return ((b & 0xFF) - 0x80);
}

就这样！您现在应该能够使用纯套接字进行双向通信。为了完整起见，我将添加完整的 Java 类。它能够使用 websockets 与客户端接收和发送消息。

package javaapplication5;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.HashMap;
import sun.misc.BASE64Encoder;

/**
 *
 * @author
 * Anders
 */
public class WebsocketServer {

    public static final int MASK_SIZE = 4;
    public static final int SINGLE_FRAME_UNMASKED = 0x81;
    private ServerSocket serverSocket;
    private Socket socket;

    public WebsocketServer() throws IOException {
    serverSocket = new ServerSocket(2005);
    connect();
    }

    private void connect() throws IOException {
    System.out.println("Listening");
    socket = serverSocket.accept();
    System.out.println("Got connection");
    if(handshake()) {
        listenerThread();
    }
    }

    private boolean handshake() throws IOException {
    PrintWriter out = new PrintWriter(socket.getOutputStream());
    BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

    HashMap<String, String> keys = new HashMap<>();
    String str;
    //Reading client handshake
    while (!(str = in.readLine()).equals("")) {
        String[] s = str.split(": ");
        System.out.println();
        System.out.println(str);
        if (s.length == 2) {
        keys.put(s[0], s[1]);
        }
    }
    //Do what you want with the keys here, we will just use "Sec-WebSocket-Key"

    String hash;
    try {
        hash = new BASE64Encoder().encode(MessageDigest.getInstance("SHA-1").digest((keys.get("Sec-WebSocket-Key") + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11").getBytes()));
    } catch (NoSuchAlgorithmException ex) {
        ex.printStackTrace();
        return false;
    }

    //Write handshake response
    out.write("HTTP/1.1 101 Switching Protocols\r\n"
        + "Upgrade: websocket\r\n"
        + "Connection: Upgrade\r\n"
        + "Sec-WebSocket-Accept: " + hash + "\r\n"
        + "\r\n");
    out.flush();

    return true;
    }

    private byte[] readBytes(int numOfBytes) throws IOException {
    byte[] b = new byte[numOfBytes];
    socket.getInputStream().read(b);
    return b;
    }

    public void sendMessage(byte[] msg) throws IOException {
    System.out.println("Sending to client");
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    BufferedOutputStream os = new BufferedOutputStream(socket.getOutputStream());
    baos.write(SINGLE_FRAME_UNMASKED);
    baos.write(msg.length);
    baos.write(msg);
    baos.flush();
    baos.close();
    convertAndPrint(baos.toByteArray());
    os.write(baos.toByteArray(), 0, baos.size());
    os.flush();
    }

    public void listenerThread() {
    Thread t = new Thread(new Runnable() {
        @Override
        public void run() {
        try {
            while (true) {
            System.out.println("Recieved from client: " + reiceveMessage());
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        }
    });
    t.start();
    }

    public String reiceveMessage() throws IOException {
    byte[] buf = readBytes(2);
    System.out.println("Headers:");
    convertAndPrint(buf);
    int opcode = buf[0] & 0x0F;
    if (opcode == 8) {
        //Client want to close connection!
        System.out.println("Client closed!");
        socket.close();
        System.exit(0);
        return null;
    } else {
        final int payloadSize = getSizeOfPayload(buf[1]);
        System.out.println("Payloadsize: " + payloadSize);
        buf = readBytes(MASK_SIZE + payloadSize);
        System.out.println("Payload:");
        convertAndPrint(buf);
        buf = unMask(Arrays.copyOfRange(buf, 0, 4), Arrays.copyOfRange(buf, 4, buf.length));
        String message = new String(buf);
        return message;
    }
    }

    private int getSizeOfPayload(byte b) {
    //Must subtract 0x80 from masked frames
    return ((b & 0xFF) - 0x80);
    }

    private byte[] unMask(byte[] mask, byte[] data) {
    for (int i = 0; i < data.length; i++) {
        data[i] = (byte) (data[i] ^ mask[i % mask.length]);
    }
    return data;
    }

    private void convertAndPrint(byte[] bytes) {
    StringBuilder sb = new StringBuilder();
    for (byte b : bytes) {
        sb.append(String.format("%02X ", b));
    }
    System.out.println(sb.toString());
    }

    public static void main(String[] args) throws IOException, InterruptedException, NoSuchAlgorithmException {
    WebsocketServer j = new WebsocketServer();
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    while (true) {
        System.out.println("Write something to the client!");
        j.sendMessage(br.readLine().getBytes());
    }
    }
}

以及一个简单的 html 客户端：

<!DOCTYPE HTML>
<html>
<body>

<button type="button" onclick="connect();">Connect</button>
<button type="button" onclick="connection.close()">Close</button>


<form>
<input type="text" id="msg" />

<button type="button" onclick="sayHello();">Say Hello!</button>

<script>
var connection;



function connect() {
    console.log("connection");
    connection = new WebSocket("ws://localhost:2005/");
    // Log errors
connection.onerror = function (error) {
  console.log('WebSocket Error ');
  console.log(error);

};

// Log messages from the server
connection.onmessage = function (e) {
  console.log('Server: ' + e.data); 
  alert("Server said: " + e.data);
};

connection.onopen = function (e) {
console.log("Connection open...");
}

connection.onclose = function (e) {
console.log("Connection closed...");
}
}


function sayHello() {
    connection.send(document.getElementById("msg").value);
}

function close() {
    console.log("Closing...");
    connection.close();
}
</script>
</body>

</html>

希望这会澄清一些事情，并且我对此有所了解:)

Answer 2

使用来自客户端的 jQuery ajax 请求，并在服务器端使用休息服务。
这里关于使用 Rest Service 创建战争模块

第一条（休息服务）

这里是关于 jQuery ajax

第 2 条（jQuery Ajax）

要编写 Java 套接字服务器，您只需要创建主程序

  try
  {
     final ServerSocket ss = new ServerSocket(8001);

     while (true)
     {
        final Socket s = ss.accept();
        // @todo s.getInputStream();
     }
  }
  catch (final IOException ex)
  {
     //
  }

它是服务器部分的主要级联

Answer 3

尝试阅读此博客。它涵盖了如何使用 spring 框架来完成你的工作。如果尚未添加，应尽快添加全面支持。

http://keaplogik.blogspot.com.au/2012/05/atmosphere-websockets-comet-with-spring.html?m=1

我还建议检查春季发行说明。

Answer 4

You are running GlassFish. Web sockets are not enabled by default in it. To enable them you must execute the following single-line command on your domain:

asadmin set configs.config.server-config.network-config.protocols.protocol.http-listener-1.http.websockets-support-enabled=true

---

HttpServlet.init(...) method is called by the servlet container to indicate to a servlet that the servlet is being placed into service.* So, your log message there doesn't represent the truth.

Answer 5

这与上面的代码相同，只是它允许您从客户端接收超过 126 个字节的消息。很多web socket源代码都没有搞清楚分片。

 // Modified code from Anders, - Christopher Price
package GoodExample;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.HashMap;
import sun.misc.BASE64Encoder;

public class JfragWS {

public static final int MASK_SIZE = 4;
public static final int SINGLE_FRAME_UNMASKED = 0x81;
private ServerSocket serverSocket;
private Socket socket;

public JfragWS() throws IOException {
serverSocket = new ServerSocket(1337);
connect();
}

private void connect() throws IOException {
System.out.println("Listening");
socket = serverSocket.accept();
System.out.println("Got connection");
if(handshake()) {
    listenerThread();
}
}

private boolean handshake() throws IOException {
PrintWriter out = new PrintWriter(socket.getOutputStream());
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

HashMap<String, String> keys = new HashMap<>();
String str;
//Reading client handshake
while (!(str = in.readLine()).equals("")) {
    String[] s = str.split(": ");
    System.out.println();
    System.out.println(str);
    if (s.length == 2) {
    keys.put(s[0], s[1]);
    }
}
//Do what you want with the keys here, we will just use "Sec-WebSocket-Key"

String hash;
try {
    hash = new BASE64Encoder().encode(MessageDigest.getInstance("SHA-1").digest((keys.get("Sec-WebSocket-Key") + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11").getBytes()));
} catch (NoSuchAlgorithmException ex) {
    ex.printStackTrace();
    return false;
}

//Write handshake response
out.write("HTTP/1.1 101 Switching Protocols\r\n"
    + "Upgrade: websocket\r\n"
    + "Connection: Upgrade\r\n"
    + "Sec-WebSocket-Accept: " + hash + "\r\n"
     + "Origin: http://face2fame.com\r\n"
    + "\r\n");

out.flush();

return true;
}

private byte[] readBytes(int numOfBytes) throws IOException {
byte[] b = new byte[numOfBytes];
socket.getInputStream().read(b);
return b;
}

public void sendMessage(byte[] msg) throws IOException {
System.out.println("Sending to client");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
BufferedOutputStream os = new BufferedOutputStream(socket.getOutputStream());
baos.write(SINGLE_FRAME_UNMASKED);
baos.write(msg.length);
baos.write(msg);
baos.flush();
baos.close();
convertAndPrint(baos.toByteArray());
os.write(baos.toByteArray(), 0, baos.size());
os.flush();
}

public void listenerThread() {
Thread t = new Thread(new Runnable() {
    @Override
    public void run() {
    try {
        while (true) {
        System.out.println("Recieved from client: " + reiceveMessage());
        System.out.println("Enter data to send");
        }
    } catch (IOException ex) {
        ex.printStackTrace();
    }
    }
});
t.start();
}

public String reiceveMessage() throws IOException {
String EasyBytes = null;
byte[] buf = readBytes(2); // our initial header

convertAndPrint(buf);
//System.exit(0);
EasyBytes = (String.format("%02X ", buf[1]));
int payloadadder = 0;
if (EasyBytes.contains("FE")){ // Indicates extended message
    byte[] buf2 = readBytes(1);
    int a = (buf2[0] & 0xff) + 1; // if byte is zero there is one extra fragment so add 1!
    System.out.println("Number of extra bytes" + a);
    payloadadder = 2; // account for original header size
    byte[] adder = null;
    //String MagnificentString = "";
    for (int x = 0; x < a; x++){
        if(x==0){
        adder = readBytes(1);
        //MagnificentString += String.format("%02X ", adder[0]);
        payloadadder += ((adder[0] & 0xFF) - 0x80);}
        if(x==1){
        payloadadder =  (buf[1] & 0xFF) + (adder[0] & 0xFF);

        }
        if(x>1){
            payloadadder = (Integer.parseInt((String.format("%02X", buf2[0]) + String.format("%02X", adder[0])), 16));
            //System.out.println(String.format("%02X", buf2[0]) + String.format("%02X", adder[0]));
            }


    }
    System.out.println("Overflow in byte/s " + payloadadder);
    //System.out.println("Our Hex String " + MagnificentString);
    //System.exit(0);
}
//convertAndPrint(buf);
//dont use this byte[] buf2 = readBytes(4);

System.out.println("Headers:");

//convertAndPrint(buf2);// Check out the byte sizes
int opcode = buf[0] & 0x0F;
if (opcode == 8) {
    //Client want to close connection!
    System.out.println("Client closed!");
    socket.close();
    System.exit(0);
    return null;
} else {
    int payloadSize = 0;
    if (payloadadder <= 0){
 payloadSize = getSizeOfPayload(buf[1]);}
    else {
        payloadSize = getSizeOfPayload(buf[1]) + payloadadder;
    }
//  if (extendedsize>=126){   
    //payloadSize = extendedsize;}
    System.out.println("Payloadsize: " + payloadSize);
    buf = readBytes(MASK_SIZE + payloadSize);
    System.out.println("Payload:");
    convertAndPrint(buf);
    buf = unMask(Arrays.copyOfRange(buf, 0, 4), Arrays.copyOfRange(buf, 4, buf.length));

    String message = new String(buf);

    return message;
}
}

private int getSizeOfPayload(byte b) {
//Must subtract 0x80 from masked frames

int a = b & 0xff;
//System.out.println("PAYLOAD SIZE INT" + a);
return ((b & 0xFF) - 0x80);
}

private byte[] unMask(byte[] mask, byte[] data) {
for (int i = 0; i < data.length; i++) {
    data[i] = (byte) (data[i] ^ mask[i % mask.length]);
}
return data;
}
private boolean convertAndPrintHeader(byte[] bytes) {
   StringBuilder sb = new StringBuilder();
   String CaryOverDetection = new String();
   // We must test byte 2 specifically for this. In the next step we add length bytes perhaps?
   //for(int i = 0; i < bytes.length; i++) {
       //}
    for (byte b : bytes) {
        CaryOverDetection = (String.format("%02X ", b));
        if (CaryOverDetection.contains("FE")){

            return false;
        }
        sb.append(String.format("%02X ", b));
    }
    System.out.println(sb.toString());
    return true;

    }

private void convertAndPrint(byte[] bytes) {
StringBuilder sb = new StringBuilder();
for (byte b : bytes) {
    sb.append(String.format("%02X ", b));
}
System.out.println(sb.toString());
}

public static void main(String[] args) throws IOException, InterruptedException, NoSuchAlgorithmException {
JfragWS j = new JfragWS();
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while (true) {
   System.out.println("Write something to the client!");
   j.sendMessage(br.readLine().getBytes());
}
}
}

Answer 6

您还可以使用现有的框架来实现这一点，例如：jWebsocket