Java xml-DSL中的Camel谓词示例

如何在Spring DSL中实现以下谓词示例：

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();

像这样：

<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>

${header.type}=='widget'
${header.type}=='wombat'

所需的简单元素（请参阅）为

${header.type}=='widget'

---

请注意，字段表达式是如何被${}包围的，后面是OGNL语法，用于比较，这不是字段表达式本身的一部分。

如果目标是在SpringXMLDSL中使用谓词，那么这将更合适-

<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> 

Spring应用程序上下文在标头中没有name属性，根本不存在。您的camel和Spring版本是什么？无论如何，您可以在中尝试此操作，而不是在谓词中：${header.type=='wombat'}此操作的语法错误。看看Dhiraj的答案。${header.type=='widget'}不起作用。使用Dhiraj提到的${header.type}=='widget'。

<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>