java 多线程发消息

### Java 中实现多线程发送消息的功能 在 Java 中，可以通过创建多个线程来并行执行任务。对于发送消息的任务，可以利用 `Runnable` 接口或者继承 `Thread` 类的方式来定义每个线程的行为。以下是基于引用中的内容和标准实践的一个完整示例。 #### 使用 Runnable 接口实现多线程发送 HTTP 请求 下面是一个简单的例子，展示如何使用多线程机制发送 HTTP 请求： ```java import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.URL; public class HttpMessageSender implements Runnable { private String url; private String message; public HttpMessageSender(String url, String message) { this.url = url; this.message = message; } @Override public void run() { try { URL obj = new URL(url); HttpURLConnection con = (HttpURLConnection) obj.openConnection(); // 设置请求方法为 POST con.setRequestMethod("POST"); con.setDoOutput(true); OutputStream os = con.getOutputStream(); os.write(message.getBytes()); os.flush(); os.close(); int responseCode = con.getResponseCode(); System.out.println("URL: " + url + ", Response Code: " + responseCode); } catch (Exception e) { System.err.println("Error sending message to URL: " + url); e.printStackTrace(); } } public static void main(String[] args) throws InterruptedException { String targetUrl = "http://example.com/api"; Thread thread1 = new Thread(new HttpMessageSender(targetUrl, "Hello from Thread 1")); Thread thread2 = new Thread(new HttpMessageSender(targetUrl, "Hello from Thread 2")); thread1.start(); thread2.start(); thread1.join(); // 主线程等待子线程完成 thread2.join(); } } ``` 上述代码展示了如何通过两个独立的线程分别向目标地址发送不同的消息[^3]。注意以下几点： - 每个线程都实现了 `Runnable` 接口，并重写了其 `run()` 方法。 - 在主线程中启动了两个子线程并通过调用 `join()` 来确保它们完成后程序才退出。 #### 基于 TCP 的 Socket 消息传递 如果需要通过 TCP 协议进行消息传输，则可参考如下代码片段： ```java import java.io.DataOutputStream; import java.io.IOException; import java.net.Socket; class TcpClient extends Thread { private final String serverAddress; private final int port; private final String message; public TcpClient(String address, int p, String msg) { this.serverAddress = address; this.port = p; this.message = msg; } @Override public void run() { try (Socket socket = new Socket(serverAddress, port)) { DataOutputStream outToServer = new DataOutputStream(socket.getOutputStream()); outToServer.writeBytes(message + '\n'); System.out.println("Sent Message Over TCP: " + message); } catch (IOException ex) { System.err.println("Failed to send TCP message."); ex.printStackTrace(); } } public static void main(String[] args) { TcpClient clientOne = new TcpClient("localhost", 9876, "Greeting from Client One!"); TcpClient clientTwo = new TcpClient("localhost", 9876, "Another greeting!"); clientOne.start(); clientTwo.start(); } } ``` 此部分演示了如何构建客户端类以异步方式连接到指定端口上的服务器并向其发送数据包[^1]。 --- #### UDP 广播或多播场景下的应用实例 当涉及到广播或组播时，通常会采用 UDP 而不是 TCP，因为后者更适合一对一可靠通讯而前者支持一对多高效传播特性。这里给出一段基础示范代码用于说明目的: ```java import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; public class UdpBroadcaster extends Thread { private final byte[] data; private final InetAddress groupAddr; private final int portNumber; public UdpBroadcaster(byte[] d, InetAddress addr, int portNo){ super(); this.data=d; this.groupAddr=addr; this.portNumber=portNo; } @Override public void run(){ DatagramSocket udpSocket=null; try{ udpSocket=new DatagramSocket(); DatagramPacket packet= new DatagramPacket(data,data.length, groupAddr,portNumber); udpSocket.send(packet); System.out.printf("Broadcasted %d bytes via UDP.\n",data.length); }catch(IOException ioEx){ System.err.println(ioEx.getMessage()); }finally{ if(udpSocket!=null && !udpSocket.isClosed()){ udpSocket.close(); } } } public static void main(String []args)throws Exception{ String text="This is a test broadcast."; byte[] buffer=text.getBytes(); InetAddress multicastGroup=InetAddress.getByName("230.0.0.1"); UdpBroadcaster broadcasterA=new UdpBroadcaster(buffer,multicastGroup,4446); UdpBroadcaster broadcasterB=new UdpBroadcaster(("Second "+text).getBytes(),multicastGroup,4446); broadcasterA.start(); broadcasterB.start(); } } ``` 该样例体现了如何借助 UDP 进行简单的信息扩散操作[^2]。 ---