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Spring MVC - SseEmitter Examples

Spring MVC 

SseEmitter is spring support class for Server-Sent Events (SSE). 

package com.logicbig.example;

import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;

import java.math.BigDecimal;
import java.time.LocalTime;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

@Controller
public class MyWebController {

    @RequestMapping("/sseTest")
    public SseEmitter handleRequest () {

        final SseEmitter emitter = new SseEmitter();
        ExecutorService service = Executors.newSingleThreadExecutor();
        service.execute(() -> {
            for (int i = 0; i < 500; i++) {
                try {
                    emitter.send(LocalTime.now().toString() , MediaType.TEXT_PLAIN);

                    Thread.sleep(200);
                } catch (Exception e) {
                    e.printStackTrace();
                    emitter.completeWithError(e);
                    return;
                }
            }
            emitter.complete();
        });

        return emitter;
    }
}
Original Post




SseEmitter uses HttpMessageConverter for type conversion. 

package com.logicbig.example;

import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;

import java.math.BigDecimal;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

@Controller
public class MyWebController2 {

    @RequestMapping("/test2")
    public SseEmitter handleRequest () {

        final SseEmitter emitter = new SseEmitter();
        ExecutorService service = Executors.newSingleThreadExecutor();
        service.execute(() -> {
            for (int i = 0; i < 1000; i++) {
                try {
                    //an HttpMessageConverter will convert BigDecimal in proper format
                    emitter.send(new BigDecimal(i));
                    emitter.send(" - ", MediaType.TEXT_PLAIN);

                    Thread.sleep(10);
                } catch (Exception e) {
                    e.printStackTrace();
                    emitter.completeWithError(e);
                    return;
                }
            }
            emitter.complete();
        });

        return emitter;
    }
}
Original Post




SseEmitter can be used as the body of ResponseEntity: 

package com.logicbig.example;

import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

@Controller
public class MyWebController3 {

    @RequestMapping("/test3")
    public ResponseEntity<SseEmitter> handleRequest () {

        final SseEmitter emitter = new SseEmitter();
        ExecutorService service = Executors.newSingleThreadExecutor();
        service.execute(() -> {
            for (int i = 0; i < 1000; i++) {
                try {
                    emitter.send(i + " - ", MediaType.TEXT_PLAIN);

                    Thread.sleep(10);
                } catch (Exception e) {
                    e.printStackTrace();
                    emitter.completeWithError(e);
                    return;
                }
            }
            emitter.complete();
        });

        return new ResponseEntity(emitter, HttpStatus.OK);
    }
}
Original Post

See Also