服务器：Tomcat 7.0.xx
在Servlet的doGet方法中添加以下代码：

String str = request.getParameter("username");
byte[] bytes = str.getBytes("iso-8859-1");
str = new String(bytes, "utf-8");

例子：

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String str = request.getParameter("username");
        byte[] bytes = str.getBytes("iso-8859-1");
        str = new String(bytes, "utf-8");

        System.out.println(str);
    }

当服务器：Tomcat 8.0.xx时，不需要输入 以上代码，可以直接输出

例子：

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String str = request.getParameter("username");
        System.out.println(str);
    }