Page Comparison

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As an example, suppose we want to update our website every five minutes with the latest stock quotes. Since we can receive multiple quotes for the same stock within our designated time period, we only want to keep the last one (since it is the most up-to-date. We can accomplish this with the aggregator:needed to aggregate responses from several different financial institutions to gather their quote for a specific loan request. Our strategy is to pick the institution with the best quote. We will need to implement some criteria to determine the cheapest loan and use our aggregation strategy to perform it.

<route>
        <from uri="jms:topic:loan:qoute"/>
        <aggregate strategyRef="bestQuote">
                <correlationExpression>
                        <header>loanId</header>
                </correlationExpression>
                <completionPredicate>
                        <simple>${header.CamelAggregatedSize} > 2</simple>
                </completionPredicate>
        </aggregate>
        <to uri="jsmith:bestQuote"/>
</route>

<bean id="bestQuote"
        class="com.mycompany.BestQuoteProcess"/>

NOTE: In this example, we are using simple language to declare the completion predicate. It is a basic language that only supports a primitive set of operators. The operation of ${header. CamelAggregatedSize} will get the header that contains the number of messages aggregated.

XML DSL Simple Example

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However, if the completed predicate that is required is more complex, then we can invoke a method call ton a Bean so we can do a more complex evaluation using pure Java code:

Code Block
<completionPredicate> <method bean="quoteService" method="isComplete"/> </compledtionPrediacate> public boolean isComplete(@Header(Exchange.AGGREGATED_SIZE) int count, String body) { return body.equals("STOP"); }

NOTE: Notice how, in this example, we are using a Bean Binding Parameter to get the aggregation size as a parameter. This frees us from having to search for it within the message.