action="#{travelBean.travelInfo}"是一种操作方法.搜索适当的方法时，只有value方法会将travelInfo从EL表达式转换为getTravelInfo().在操作方法中，托管bean中应该确实存在travelInfo()方法，但实际上并非如此.

action="#{travelBean.travelInfo}" is an action method. Only value methods converts travelInfo from EL expression to getTravelInfo() when searching for appropriate method. In action method exactly travelInfo() method is expected to be present in your managed bean, but it isn't.