可以混合用。文檔有說明：
Spring can accommodate both styles and even mix them together.
混合用的話，有個先后順序，xml配置會覆蓋annotation。原文：
Annotation injection is performed before XML injection, thus the latter configuration will override the former for properties wired through both approaches.
也就是說對於同一個bean 不能注解完成部分屬性的設定 xml完成部分屬性的設定
xml會覆蓋注解