Only one AsyncAnnotationBeanPostProcessor may exist within the context.

I had this problem when I copied applicationContext.xml and created new one called applicationContextAdditional.xml. I didn‘t try to find the reason, but both contained namespace

<bean ...
    xmlns:task="http://www.springframework.org/schema/task"
    ...
    xsi:schemaLocation="
   http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.0.xsd" >

    ...

</bean>

when I removed the namespace from the second one my problem was solved. Maybe it helps someone.

红色命名空间出现2次。

This happens when spring parses the <task:annotation-driven/> text twice in a config XML.

For me this was happening because both applicationContext-root.xml and applicationContext-where-annotation-driven-is-specififed.xml were imported in my WEB.xml in <context-param>section.

Leaving only applicationContext-root.xml in WEB.xml solved the issue.