可以混合用。文档有说明：
Spring can accommodate both styles and even mix them together.
混合用的话，有个先后顺序，xml配置会覆盖annotation。原文：
Annotation injection is performed before XML injection, thus the latter configuration will override the former for properties wired through both approaches.
也就是说对于同一个bean 不能注解完成部分属性的设定 xml完成部分属性的设定
xml会覆盖注解