Comparing those frameworks with .net ;

Struts is basically the implemenation of MVC architecture. It 's use is similar to the MVC webproject in .net .

As fu*ketoow said, Spring is little more complicated than Struts because it has different modules you can use separately. You can use component of spring to replace struts and hibernate both. But mostly, it is used in business layer 

Hibernate is used for application persistence. The .net version of hibernate is NHibernate. Entity framework in .net is later developed by microsoft to replace opensource framework NHibernate.  So i believe you know why hibernate is used .

If you integrate all these three frameworks in one project , the project contents would be like as [Disallowed String for - Bad word 'fuk']etoow said .

Struts - presentation/view with controller 
Spring -business layer
Hibernate -Persistence