camel系列-复合消息处理器

发表于 更新于

概念

使用组合消息处理器来处理组合消息。组合消息处理器将消息拆分，将子消息路由到适当的目的地，并将响应重新聚合回单个消息。

示例说明

  1. 拆分处理
    1. 使用 split 对消息进行拆分
    2. 使用 bean 为 MyOrderService 的 handleOrder 方法进行单条消息处理
    3. 自定义 MyOrderStrategy 聚合策略，对输出结果消息进行聚合处理
  2. 拆分处理结束标识：处理完之后使用 end 方法说明结束标识
  3. 聚合处理：使用 bean 为 MyOrderService 的 buildCombinedResponse 方法进行聚合的结果消息进行处理
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
public class SplitAggregateInOutTest extends ContextTestSupport {

    private static final Logger LOG = LoggerFactory.getLogger(SplitAggregateInOutTest.class);

    private String expectedBody = "Response[(id=1,item=A);(id=2,item=B);(id=3,item=C)]";

    @Test
    public void testSplitAndAggregateInOut() throws Exception {
        MockEndpoint mock = getMockEndpoint("mock:result");
        mock.expectedBodiesReceived(expectedBody);

        // use requestBody as its InOut
        Object out = template.requestBody("direct:start", "A@B@C");
        assertEquals(expectedBody, out);
        LOG.debug("Response to caller: " + out);

        assertMockEndpointsSatisfied();
    }

    @Override
    protected Registry createRegistry() throws Exception {
        Registry jndi = super.createRegistry();
        jndi.bind("MyOrderService", new MyOrderService());
        return jndi;
    }

    @Override
    protected RouteBuilder createRouteBuilder() throws Exception {
        return new RouteBuilder() {
            @Override
            public void configure() throws Exception {
                // START SNIPPET: e1
                // this routes starts from the direct:start endpoint
                // the body is then splitted based on @ separator
                // the splitter in Camel supports InOut as well and for that we
                // need
                // to be able to aggregate what response we need to send back,
                // so we provide our
                // own strategy with the class MyOrderStrategy.
                from("direct:start").split(body().tokenize("@"), new MyOrderStrategy())
                        // each splitted message is then send to this bean where we
                        // can process it
                        .to("bean:MyOrderService?method=handleOrder")
                        // this is important to end the splitter route as we do not
                        // want to do more routing
                        // on each splitted message
                        .end()
                        // after we have splitted and handled each message we want
                        // to send a single combined
                        // response back to the original caller, so we let this bean
                        // build it for us
                        // this bean will receive the result of the aggregate
                        // strategy: MyOrderStrategy
                        .to("bean:MyOrderService?method=buildCombinedResponse")
                        // END SNIPPET: e1
                        .to("mock:result");
            }
        };
    }

    // START SNIPPET: e2
    public static class MyOrderService {

        private static int counter;

        /**
         * We just handle the order by returning a id line for the order
         */
        public String handleOrder(String line) {
            LOG.debug("HandleOrder: " + line);
            return "(id=" + ++counter + ",item=" + line + ")";
        }

        /**
         * We use the same bean for building the combined response to send back to the original caller
         */
        public String buildCombinedResponse(String line) {
            LOG.debug("BuildCombinedResponse: " + line);
            return "Response[" + line + "]";
        }
    }
    // END SNIPPET: e2

    // START SNIPPET: e3
    /**
     * This is our own order aggregation strategy where we can control how each splitted message should be combined. As
     * we do not want to loos any message we copy from the new to the old to preserve the order lines as long we process
     * them
     */
    public static class MyOrderStrategy implements AggregationStrategy {

        @Override
        public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
            // put order together in old exchange by adding the order from new
            // exchange

            if (oldExchange == null) {
                // the first time we aggregate we only have the new exchange,
                // so we just return it
                return newExchange;
            }

            String orders = oldExchange.getIn().getBody(String.class);
            String newLine = newExchange.getIn().getBody(String.class);

            LOG.debug("Aggregate old orders: " + orders);
            LOG.debug("Aggregate new order: " + newLine);

            // put orders together separating by semi colon
            orders = orders + ";" + newLine;
            // put combined order back on old to preserve it
            oldExchange.getIn().setBody(orders);

            // return old as this is the one that has all the orders gathered
            // until now
            return oldExchange;
        }
    }
    // END SNIPPET: e3

}

参考：