使用Spring Boot实现Server-Sent Events（SSE）的完整指南

import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.http.ResponseEntity;
import org.springframework.http.concurrent.PushStreamHttpHeaders;
 
import javax.servlet.http.PushBuilder;
import java.io.PrintWriter;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
 
@RestController
public class ServerSentEventsController {
 
    @GetMapping(path = "/subscribe", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
    public ResponseEntity<PushStreamHttpHeaders> subscribe(PushBuilder pushBuilder) {
        PushStreamHttpHeaders headers = new PushStreamHttpHeaders();
        ExecutorService executorService = Executors.newSingleThreadExecutor();
 
        executorService.execute(() -> {
            try {
                PrintWriter writer = pushBuilder.pushToTarget("/queue/events")
                        .setContentType(MediaType.TEXT_EVENT_STREAM)
                        .getWriter();
                writer.printf("data: %s%n%n", "Initializing connection...");
                writer.flush();
 
                // 模拟发送事件
                for (int i = 0; i < 5; i++) {
                    writer.printf("data: %s%n%n", "Event " + i);
                    writer.flush();
                    Thread.sleep(1000);
                }
 
                writer.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        });
 
        return ResponseEntity.ok().headers(headers).build();
    }
}

这段代码示例展示了如何在Spring Boot应用中使用PushBuilder来推送Server-Sent Events。它定义了一个简单的REST接口/subscribe，当被调用时，它会启动一个新线程来发送事件。每个事件都以"data: "开头，并以换行符结束，然后通过PushBuilder的pushToTarget方法推送到客户端的/queue/events路径。这个例子提供了一个简单的模型，用于理解如何在实际应用中实现SSE。