xml DSL 中的骆驼谓词示例

Question

How can I implement following Predicate Example given in Spring DSL:

Predicate isWidget = header("type").isEqualTo("widget");

from("jms:queue:order")
   .choice()
      .when(isWidget).to("bean:widgetOrder")
      .when(isWombat).to("bean:wombatOrder")
   .otherwise()
      .to("bean:miscOrder")
   .end();

Answer 1

Like this:

<route>
  <from uri="jms:queue:order"/>
  <choice>
    <when>
       <simple>${header.type} == 'widget'</simple>
       <to uri="bean:widgetOrder"/>
    </when>
    <when>
      <simple>${header.type} == 'wombat'</simple>
      <to uri="bean:wombatOrder"/>
    </when>
    <otherwise>
      <to uri="bean:miscOrder"/>
    </otherwise>
  </choice>
</route>

Answer 2

The required simple element (see accepted answer ) is

<simple>${header.type} == 'widget'</simple>

Notice how the field expression is surrounded by ${} followed by OGNL syntax for comparison, which is not part of the field expression itself.

Answer 3

IF the objective is to make use of a Predicate in Spring XML DSL then this would be more appropriate -

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:camel="http://camel.apache.org/schema/spring"
xsi:schemaLocation="
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
            http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">

<camel:camelContext trace="true">
    <camel:route>
        <camel:from uri="jms:queue:order" />
        <camel:filter>
            <camel:method ref="myPredicate" />
            <to uri="bean:widgetOrder"/>
        </camel:filter>
    </camel:route>
</camel:camelContext>

<bean id="myPredicate" class="MyPredicate"/>
</beans>