java - 如何在Camel中循环后访问聚合消息

Question

Camel 2.16.1 Loop 之后如何获取聚合消息？我得到的唯一输出是循环中处理的最后一条消息。

我的循环迭代了三次，并且有一个聚合器将主体组合在单个字符串中。循环如下所示:

from("timer:begin?repeatCount=1&delay=1")
.routeId("timer")
.to("direct:loop")
.log("Body after Loop Route: ${body}");

from("direct:loop")
.routeId("loop")
.loop(3)
    .setBody().simple("Hello ${exchangeProperty.CamelLoopIndex}")
    .log("Body in Loop: ${body}")
    .aggregate(new AggregationStrategy() {

        public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
            if (oldExchange == null) {
                return newExchange;
            }
            else {
                String oldBody = oldExchange.getIn().getBody(String.class);
                String newBody = oldBody + ", " + newExchange.getIn().getBody(String.class);
                newExchange.getIn().setBody(newBody);
                return newExchange;
            }
        }
    }).constant(true).completionSize(3)
    .log("Body after Aggregate: ${body}")
.end();

问题是在计时器路由中我无法访问聚合消息。相反，示例中的计时器路由输出Hello 2，如下所示:

Body in Loop: Hello 0
Body in Loop: Hello 1
Body in Loop: Hello 2
Body after Aggregate: Hello 0, Hello 1, Hello 2
Body after Loop Route: Hello 2

Answer 1

我不知道如何使用 Loop 来做到这一点。然而Camel网站上说Loop是

Useful mostly during testing.

所以我走了另一条路。

因此，为了像循环一样迭代某些值并获取聚合结果，我修改了路线以使用 Splitter和 Aggregator像这样

from("timer:begin?repeatCount=1&delay=1")
.routeId("timer")
.to("direct:splitter-loop")
.log("Body after Loop Route: ${body}");

from("direct:splitter-loop")
.routeId("splitter-loop")
.process(exchange -> {
    // Add items that you want to iterate over to body or header
    // and later use splitter over those items.
    List<String> loopIndex = new ArrayList<String>();
    loopIndex.add("1");
    loopIndex.add("2");
    loopIndex.add("3");
    exchange.getOut().setBody(loopIndex);
})
.split(body(), new StringAggregator())
    .setBody().simple("Hello ${body}")
    .log("Body in Loop: ${body}")
.end()
.log("Body after Aggregate: ${body}");

其中 StringAggregator 与之前一样:

public class StringAggregator implements AggregationStrategy {

    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        if (oldExchange == null) {
            return newExchange;
        }
        else {
            String oldBody = oldExchange.getIn().getBody(String.class);
            String newBody = oldBody + ", " + newExchange.getIn().getBody(String.class);
            newExchange.getIn().setBody(newBody);
            return newExchange;
        }
    }
}

这条路线现在给了我想要的聚合结果，如下所示

Body in Loop: Hello 1
Body in Loop: Hello 2
Body in Loop: Hello 3
Body after Aggregate: Hello 1, Hello 2, Hello 3
Body after Loop Route: Hello 1, Hello 2, Hello 3