servlet defaults to single-instance multithreading mode, so linear security problems may occur. One solution is to implement the SingleThreadModel interface, but this method is not recommended. It is said that this method consumes a lot of memory resources when the concurrency is high. (because the implementation of this interface, that is, each request, will create a servlet instance, which is multiple instances, which will take up a lot of memory),. But isn"t it the default in struts2 to create an action for every request? why doesn"t anyone say that struts2 consumes a lot of memory resources?