我在eclipse中创建一个简单的JPA项目来运行glassfish。我收到以下错误：
cannot Deploy GuardApplicationEAR
Deployment Error for module: GuardApplicationEAR: Error occurred during deployment: Exception while preparing the app : Invalid resource : jdbc/_default__pm. Please see server.log for more details.
Exception while invoking class org.glassfish.persistence.jpa.JPADeployer prepare method : java.lang.RuntimeException: Invalid resource : jdbc/_default__pm
Invalid resource : jdbc/_default__pm
我的项目中没有定义jdbc / 默认 _pm。有人可以帮帮忙。感谢。