接收批次訊息

使用 RabbitMQ 繫結器時，消費者繫結處理兩種批次類型

生產者建立的批次

一般來說，如果生產者繫結的 batch-enabled=true (請參閱 Rabbit 生產者屬性)，或訊息由 BatchingRabbitTemplate 建立，則批次的元素會以個別呼叫方式傳回給監聽器方法。從 3.0 版開始，如果 spring.cloud.stream.bindings.<name>.consumer.batch-mode 設定為 true，則任何此類批次都可以 List<?> 的形式呈現給監聽器方法。

消費者端批次處理

從 3.1 版開始，可以將消費者配置為將多個輸入訊息組合成批次，並以轉換後酬載的 List<?> 形式呈現給應用程式。以下簡單的應用程式示範如何使用此技術

spring.cloud.stream.bindings.input-in-0.group=someGroup

spring.cloud.stream.bindings.input-in-0.consumer.batch-mode=true

spring.cloud.stream.rabbit.bindings.input-in-0.consumer.enable-batching=true
spring.cloud.stream.rabbit.bindings.input-in-0.consumer.batch-size=10
spring.cloud.stream.rabbit.bindings.input-in-0.consumer.receive-timeout=200

@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

	@Bean
	Consumer<List<Thing>> input() {
		return list -> {
			System.out.println("Received " + list.size());
			list.forEach(thing -> {
				System.out.println(thing);

				// ...

			});
		};
	}

	@Bean
	public ApplicationRunner runner(RabbitTemplate template) {
		return args -> {
			template.convertAndSend("input-in-0.someGroup", "{\"field\":\"value1\"}");
			template.convertAndSend("input-in-0.someGroup", "{\"field\":\"value2\"}");
		};
	}

	public static class Thing {

		private String field;

		public Thing() {
		}

		public Thing(String field) {
			this.field = field;
		}

		public String getField() {
			return this.field;
		}

		public void setField(String field) {
			this.field = field;
		}

		@Override
		public String toString() {
			return "Thing [field=" + this.field + "]";
		}

	}

}

Received 2
Thing [field=value1]
Thing [field=value2]

批次中的訊息數量由 batch-size 和 receive-timeout 屬性指定；如果 receive-timeout 過期且沒有新訊息，則會傳遞「短」批次。

消費者端批次處理僅在使用 container-type=simple (預設值) 的情況下才支援。

如果您希望檢查消費者端批次訊息的標頭，則應消費 Message<List<?>>；標頭是 List<Map<String, Object>>，位於標頭 AmqpInboundChannelAdapter.CONSOLIDATED_HEADERS 中，其中每個酬載元素的標頭位於對應的索引中。再次強調，這是一個簡單的範例

@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

	@Bean
	Consumer<Message<List<Thing>>> input() {
		return msg -> {
			List<Thing> things = msg.getPayload();
			System.out.println("Received " + things.size());
			List<Map<String, Object>> headers =
					(List<Map<String, Object>>) msg.getHeaders().get(AmqpInboundChannelAdapter.CONSOLIDATED_HEADERS);
			for (int i = 0; i < things.size(); i++) {
				System.out.println(things.get(i) + " myHeader=" + headers.get(i).get("myHeader"));

				// ...

			}
		};
	}

	@Bean
	public ApplicationRunner runner(RabbitTemplate template) {
		return args -> {
			template.convertAndSend("input-in-0.someGroup", "{\"field\":\"value1\"}", msg -> {
				msg.getMessageProperties().setHeader("myHeader", "headerValue1");
				return msg;
			});
			template.convertAndSend("input-in-0.someGroup", "{\"field\":\"value2\"}", msg -> {
				msg.getMessageProperties().setHeader("myHeader", "headerValue2");
				return msg;
			});
		};
	}

	public static class Thing {

		private String field;

		public Thing() {
		}

		public Thing(String field) {
			this.field = field;
		}

		public String getfield() {
			return this.field;
		}

		public void setfield(String field) {
			this.field = field;
		}

		@Override
		public String toString() {
			return "Thing [field=" + this.field + "]";
		}

	}

}

Received 2
Thing [field=value1] myHeader=headerValue1
Thing [field=value2] myHeader=headerValue2