JAXB：具有文本内容和属性的元素，使用XJC生成类(JAXB: an element with textual content and attributes, generating classes with XJC)

 这不是一个观点的界限。 视图边界表示类型参数A是有界的，因为它可以作为类型B查看（转换为）。 你有什么倒置的类型和类型参数，所以它没有资格。 
 
 为了使事情更清楚， 绑定是对“自由”类型的限制 - 类型参数。 例如： 
 
type A <: String // A has an upper bound
type A >: String // A has a lower bound
 
 所以观点界限也是一个限制 - 一个通过非常不同的机制强加的界限。 因此，它只能强加在类型参数上，而不能强加在类型上。 
 
 当然，说String => A必须存在也是一种界限，但不是一个有名称或语法糖的人。 

That is not a view bound. A view bound says that a type parameter A is bounded in that it can be viewed (converted to) as a type B. What you have inverted type and type parameter, so it doesn't qualify.
 
To make things more clear, a bound is a limit on a "free" type -- a type parameter. For example:
 
type A <: String // A has an upper bound
type A >: String // A has a lower bound
 
So a view bound is also a limit -- one imposed through a very different mechanism. As such, it can only be imposed on a type parameter, not on a type.
 
Surely, saying String => A must exist is also a kind of bound, but not one that has a name or syntactic sugar for.