Servlet 实现方式及属性

@WebServlet("/myservlet")
public class MyServlet extends HttpServlet {

	public MyServlet(){
		System.out.println("实例化了："+this);
	}
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.setAttribute("msg", "用户名不存在");//设置属性
		request.getAttribute("msg");//获取属性
		request.getAttributeNames();//获取属性名字集合
		//响应重定向
//		response.sendRedirect(request.getContextPath()+"/login-fail.jsp");
		
		//请求转发
		request.getRequestDispatcher("/login-fail.jsp").forward(request, response);

		System.out.println("doGet:"+this);

		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		out.println("");
		out.println("");
		out.println("  ");
		out.println("  ");
		out.print("    This is ");
		out.print(this.getClass());
		out.println(", using the GET method");
		out.println("  ");
		out.println("");
		out.flush();
		out.close();
	}
}

@WebServlet("/myservlet")
public class MyServlet implements Servlet {

	@Override
	public void destroy() {}

	@Override
	public ServletConfig getServletConfig() {
		return null;
	}

	@Override
	public String getServletInfo() {
		return null;
	}

	@Override
	public void init(ServletConfig servletConfig) throws ServletException {}
	
	@Override
	public void service(ServletRequest request, ServletResponse response)
		throws ServletException, IOException {
	}

}

@WebServlet("/myservlet")
public class MyServlet extends GenericServlet {
	
	@Override
	public void service(ServletRequest arg0, ServletResponse arg1)
			throws ServletException, IOException {
		System.out.println(this.getServletConfig().getInitParameter("systemName"));
		System.out.println(this.getInitParameter("systemName"));
		System.out.println("service:"+this);
	}
}