@Component
public class OrderProcessingRoute extends RouteBuilder {

  @Autowired
  private PriceAggregationStrategy priceAggregationStrategy;

  @Override
  public void configure() throws Exception {
    from("direct:fetchProcess")
    .split(body(), priceAggregationStrategy).parallelProcessing()
    .to("bean:pricingService?method=calculatePrice")
    .end();
  }
}

@Component
public class PriceAggregationStrategy implements AggregationStrategy{

  @Override
  public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
    OrderLine newBody = newExchange.getIn().getBody(OrderLine.class);
        if (oldExchange == null) {
            Order order = new Order();
            order.setOrderNo(UUID.randomUUID().toString());
            order.setOrderDate(Instant.now().toString());
            order.setOrderPrice(newBody.getPrice());
            order.addOrderLine(newBody);

            newExchange.getIn().setBody(order, Order.class);
            return newExchange;
        }
        OrderLine newOrderLine = newExchange.getIn()
                                .getBody(OrderLine.class);
        Order order = oldExchange.getIn().getBody(Order.class);
        order.setOrderPrice(order.getOrderPrice() + newOrderLine.getPrice());
        order.addOrderLine(newOrderLine);
        oldExchange.getIn().setBody(order);

        return oldExchange;
  }

}

@Service
public class PricingService {

  public OrderLine calculatePrice(final OrderLine orderLine ) {
    String category = orderLine.getProduct().getProductCategory();
    if("Electronics".equalsIgnoreCase(category))
       orderLine.setPrice(300.0);
...
...
    return orderLine;

  }

}

这里我们在Java DSL中定义了一个路由，它将传入消息(订单行集合)分割为单独的订单行项目。每个订单行项目被发送到PricingService类的calculatePrice方法，以计算项目的价格。

接下来，我们在拆分步骤之后绑定了一个聚合器。聚合器实现了AggregationStrategy接口，我们的聚合逻辑位于覆盖的aggregate()方法中。在aggregate()方法中，我们获取每个订单行项，并将它们合并到单个订单对象中。

使用REST风格DSL的拆分聚合器模式来消费路由

接下来，让我们在Apache Camel中使用REST风格的DSL来定义带有HTTP请求方式(如GET、POST、PUT和DELETE)的REST api。实际的REST传输是使用camel REST组件(如Netty HTTP、Servlet)。

要在Java中使用Rest DSL，我们需要扩展RouteBuilder类，并在configure方法中定义路由，类似于前面创建常规Camel路由的方法。

让我们通过使用Java DSL中的REST构造来定义API来定义一个用于处理订单的REST服务。我们还将基于OpenAPI规范(OAS)生成API规范:

@Component
public class RestApiRoute  extends RouteBuilder {

  @Autowired
  private Environment env;

  @Override
  public void configure() throws Exception {

    restConfiguration()
        .contextPath("/ecommapp")
        .apiContextPath("/api-doc")
        .apiProperty("api.title", "REST API for processing Order")
        .apiProperty("api.version", "1.0")
        .apiProperty("cors", "true")
        .apiContextRouteId("doc-api")
        .port(env.getProperty("server.port", "8080"))
        .bindingMode(RestBindingMode.json);

    rest("/order/")
    .get("/process").description("Process order")
    .route().routeId("orders-api")
    .bean(OrderService.class, "generateOrder")
    .to("direct:fetchProcess")
    .endRest();

  }