Java中的RequestDispatcher

使用的主要目的是什么 RequestDispatcher Filter 如以下示例:

public void doFilter(ServletRequest request, ServletResponse response,
    FilterChain chain) throws ServletException, IOException {
     HttpServletRequest aHttpServletRequest = (HttpServletRequest) request;
     aHttpServletRequest.getRequestDispatcher("/init.jsp").include(request, response);
     chain.doFilter(request, response);
}