JMS Selector for messages having an underscore in one header with Camel and Blueprint - filter

Question

I need to cleanup some messages in a JMS queue (ActiveMQ) where some of the message header contains an underscore.
Some example
Message 1:
header MyObject=urn:sap:order:ID1234
body = <some xml>
Message 2:
header MyObject=urn:sap:order:ID9834_ABC
body = <some xml>
My goal is to move the only messages looking like Message 2 (and all similar containing an underscore) and not messages without underscores (like Message 1) from the original queue MY_ORDERS.
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:ext="http://aries.apache.org/blueprint/xmlns/blueprint-ext/v1.0.0"
xmlns:cm="http://aries.apache.org/blueprint/xmlns/blueprint-cm/v1.1.0"
xsi:schemaLocation="
http://www.osgi.org/xmlns/blueprint/v1.0.0 http://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd
http://camel.apache.org/schema/blueprint http://camel.apache.org/schema/blueprint/camel-blueprint.xsd
http://aries.apache.org/blueprint/xmlns/blueprint-cm/v1.1.0 http://aries.apache.org/schemas/blueprint-cm/blueprint-cm-1.1.0.xsd">
<cm:property-placeholder persistent-id="com.mycompany.order-temp" update-strategy="reload">
<cm:default-properties>
<cm:property name="amq.url" value="tcp://localhost:61616" />
<cm:property name="queue.to.dump" value="activemq:queue:MY_ORDERS?selector=MyObject+LIKE+'urn:order:%_%'" />
</cm:default-properties>
</cm:property-placeholder>
<camelContext xmlns="http://camel.apache.org/schema/blueprint">
<onException useOriginalMessage="true">
<exception>java.lang.Exception</exception>
<handled>
<constant>true</constant>
</handled>
<to uri="activemq:queue:MY_ORDERS_DLQ?preserveMessageQos=true" />
</onException>
<route id="route-orders-to-temp">
<from uri="{{queue.to.dump}}" />
<to uri="activemq:queue:MY_ORDERS_TEMP" />
</route>
</camelContext>
<bean id="activemq" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="brokerURL" value="${amq.url}" />
</bean>
</blueprint>
By using the following posts and because the official ActiveMQ Documentation about selectors says it uses SQL 92 syntax:
https://stackoverflow.com/a/17102616/628006
https://stackoverflow.com/a/5822/628006
I tried all the following combinations:
selector=MyObject+LIKE+'urn:sap:order:%_%'
selector=MyObject+LIKE+'urn:sap:order:%_%'
selector=MyObject+LIKE+'urn:sap:order:%\_%'
selector=MyObject+LIKE+'urn:sap:order:%[_]%'
selector=MyObject+LIKE+'urn:sap:order:[a-Z0-9]*_[a-Z0-9]*'
But none of them seems to work. Any thoughts?

Answer 1

Finally I found the solution of my problem: there is a special syntax to define the escaping character which does not seems to be set by default.
By looking on Internet I finally found the following post which clearly shows the underscore must be escaped by e.g. \ then defining the escape character with ESCAPE '\'
If I apply to my cases the following lines:
selector=MyObject+LIKE+'urn:sap:order:%_%' ESCAPE '\'
selector=MyObject+LIKE+'urn:sap:order:%\_%' ESCAPE '\'
will just work fine with the additional ESCAPE '\' at the end of the selector.