SpringBoot整合SSE，实现后端主动推送DEMO

前些日子写了整合SSE得demo。但是SSE对象是存储在ConcurrentHashMap<String, SseEmitter>中。在正式环境明显就不行了，服务重启一下的话都没有了。

那么要持久化，第一选择放redis

1、写了一个redis操作组件

SseEmitterStore

/**
 * 不考虑redis 连接异常问题
 * @author cmy
 * @date 2024/8/21 10:55
 */
@Component
public class SseEmitterStore {

    private ConcurrentHashMap<String, SseEmitter> emitters = new ConcurrentHashMap<>();
    @Resource
    private RedisTemplate<String, Object> redisTemplate;


    public void addEmitter(String key, SseEmitter emitter) {
        emitters.put(key, emitter);
        redisTemplate.opsForHash().put("sse-emitters", key, emitter);
    }

    public void removeEmitter(String key) {
        emitters.remove(key);
        redisTemplate.opsForHash().delete("sse-emitters", key);
    }

    @PostConstruct
    private void init() {
        Map<Object, Object> temp = redisTemplate.opsForHash().entries("sse-emitters");
        temp.forEach((key, value) -> {
            if (value instanceof SseEmitter) {
                emitters.put(key.toString(), (SseEmitter) value);
            }
        });
    }

    public ConcurrentHashMap<String, SseEmitter> getEmitters() {
        return emitters;
    }
}

Controller修改

public class SseController {


    @Resource
    SseEmitterStore sseEmitterStore;

    @GetMapping("/subscribe/{id}")
    @CrossOrigin(origins = "*")
    public SseEmitter subscribe(@PathVariable String id) {
        SseEmitter emitter = new SseEmitter(Long.MAX_VALUE);
        sseEmitterStore.addEmitter(id,emitter);
        emitter.onCompletion(() -> sseEmitterStore.removeEmitter(id));
        emitter.onError(e -> sseEmitterStore.removeEmitter(id));
        return emitter;
    }

    @GetMapping("/unbind/{id}")
    @CrossOrigin(origins = "*")
    public ServerResponse deleteItem(@PathVariable String id) {
        this.sseEmitterStore.removeEmitter(id);
        return ServerResponse.success(true);
    }
}

异步发送消息service

    @Async
    public void broadcastMessage(String message) {
        List<String> keysToDelete = new ArrayList<>();

        this.sseEmitterStore.getEmitters().forEach((k, v) -> {
            try {
                v.send(message);
            } catch (Throwable t) {
                keysToDelete.add(k);
            }
        });
        keysToDelete.forEach(this.sseEmitterStore::removeEmitter);
    }

2、无法序列化的问题

跑起来之后，结果报错

DefaultSerializer requires a Serializable payload but received an object of type [org.springframework.web.servlet.mvc.method.annotation.SseEmitter]

错误信息已经很明显了

因为 SseEmitter 并不是一个实现了 Serializable 接口的类，因此不能被默认的序列化器正确处理。

问了AI

        

3、解决无法序列化问题

3.1自定义redis自定义序列化器

public class CustomJackson2JsonRedisSerializer<T> implements RedisSerializer<T> {

    private static final long serialVersionUID = -7649863253433761554L;
    private final ObjectMapper objectMapper;

    public CustomJackson2JsonRedisSerializer() {
        this.objectMapper = new ObjectMapper();
        this.objectMapper.registerModule(new JavaTimeModule());
        this.objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
    }

    @Override
    public byte[] serialize(T t) throws SerializationException {
        if (t == null) {
            return new byte[0];
        }
        try {
            return objectMapper.writeValueAsBytes(t);
        } catch (JsonProcessingException e) {
            throw new SerializationException("Could not write JSON: " + e.getMessage(), e);
        }
    }

    @Override
    public T deserialize(byte[] bytes) throws SerializationException {
        if (bytes == null || bytes.length == 0) {
            return null;
        }
        try {
            return (T) objectMapper.readValue(bytes, SseEmitter.class);
        } catch (IOException e) {
            throw new SerializationException("Could not read JSON: " + e.getMessage(), e);
        }
    }
}

3.2redis配置，使序列化器生效

@Configuration
public class RedisConfig {

    @Bean
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) {
        RedisTemplate<String, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(factory);

        StringRedisSerializer stringSerializer = new StringRedisSerializer();
        CustomJackson2JsonRedisSerializer<Object> jacksonSerializer = new CustomJackson2JsonRedisSerializer<>();

        // 根据实际情况，自行修改
        template.setKeySerializer(stringSerializer);
        template.setValueSerializer(jacksonSerializer);
        template.setHashKeySerializer(stringSerializer);
        template.setHashValueSerializer(jacksonSerializer);

        template.afterPropertiesSet();
        return template;
    }
}

再次启动服务，即生效。