在服务器启动时，filter过滤器便开始工作，这时可以在过滤器中设置一个通用的路径，存放在Application范围中，当我们在JSP超链接重定向使用路径时便可以，直接调用这个路径，是一种软实现，省去很多麻烦

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过滤器中实现

public class MyFlilter implements Filter {
         ServletContext sc;    public void init(FilterConfig fConfig) throws ServletException {    }    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)            throws IOException, ServletException {        sc = request.getServletContext();        if (sc.getAttribute("basePath") == null) {            sc.setAttribute("basePath", request.getScheme() + "://" + request.getServerPort()                    + ((HttpServletRequest) request).getContextPath());        }        chain.doFilter(request, response);    }    public void destroy() {    }}

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在servlet中调用该地址

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        String path=(String)this.getServletContext().getAttribute("basePath");    }