web 默认servlet

当我们访问一个web项目时，仅仅输入项目名，默认会转向index.jsp，如果要使其转向默认的servlet，我们需要定义一个过滤器来实现。

<filter>
      <filter-name>dispatcher</filter-name>
      <filter-class>com.siya.util.Dispatcher</filter-class>
  </filter>
   <filter-mapping>
      <filter-name>dispatcher</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>

在过滤器中就可以对访问的url进行判断了。

public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain arg2) throws IOException, ServletException {
        HttpServletRequest req=(HttpServletRequest) request;
        HttpServletResponse resp=(HttpServletResponse) response;
        String reqUrl=req.getRequestURL().toString();
        if(reqUrl.endsWith("/")){reqUrl=reqUrl.substring(0, reqUrl.length()-1);}
        String context=req.getContextPath();
        String temurl=reqUrl.substring(reqUrl.lastIndexOf("/")+1);
        if(reqUrl.endsWith(context)){
            req.getRequestDispatcher("默认的servlet地址").forward(req, resp);
        }else{
            req.getRequestDispatcher(temurl).forward(req, resp);
        }
    }