Http Servlet 协议

@WebServlet("/test")
public class Severlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("xxxxxxxxxxxx");
    }
}

@WebServlet("/test02")
public class Servlet01 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("Serlvet 被调用了");
    }

    @Override
    public void init() throws ServletException {
        System.out.println("servlet 初始化");
    }

    @Override
    public void destroy() {
        System.out.println("servlet 销毁了");
    }
}

   protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /**
         * HttpServletRequest 的常见方法
         * */

//        1. 请求地址
        String url = req.getRequestURL() + "";
        System.out.println(url);
        System.out.println("--------------------");

//        2. 请求部分路径， 从项目站点名开始，到？前面结束
        String requestURI = req.getRequestURI();
        System.out.println(requestURI);
        System.out.println("--------------------");

//        3. 请求参数字符串
        String queryString = req.getQueryString();
        System.out.println(queryString);
        System.out.println("--------------------");

//        4. 请求方式
        String method = req.getMethod();
        System.out.println(method);
        System.out.println("--------------------");

//        5. 当前协议版本
        String protocol = req.getProtocol();
        System.out.println(protocol);
        System.out.println("--------------------");

//        6. 上下文路径
        String contextPath = req.getContextPath();
        System.out.println(contextPath);
        System.out.println("____________________");

        /**
         * 获取请求参数
         */
//        1. 获取指定参数
        String username = req.getParameter("username");
        System.out.println(username);

//        2. 获取多个  同一个参数名有多个值
        String[] xxes = req.getParameterValues("xx");
        for (String xx : xxes) {
            System.out.println(xx);
        }
    }

//        1. 转发到请求
        req.getRequestDispatcher("/test02").forward(req,resp);
//        2. 转发到html
        req.getRequestDispatcher("login.html").forward(req,resp);
//        3. 转发到jsp
        req.getRequestDispatcher("login.jsp").forward(req,resp);

        req.setAttribute("username","xxx");
        String username = (String) req.getAttribute("username");

//        1. 字符输出流
        PrintWriter writer = resp.getWriter();
        writer.write("hello 字符输出流");
//        2. 字节输出流
        ServletOutputStream outputStream = resp.getOutputStream();
        outputStream.write("hi".getBytes());

        Cookie cookie = new Cookie("username", "password");
        resp.addCookie(cookie);

        Cookie[] cookies = req.getCookies();
        if (cookies != null && cookies.length != 0){
            for (Cookie cookie : cookies) {
                System.out.println(cookie.getName());
                System.out.println(cookie.getValue());
            }
        }

        Cookie cookie = new Cookie("set", "xx");
        cookie.setPath("/xx/aa");

        HttpSession session = req.getSession();

//        1.获得唯一会话标识符
        String id = session.getId();
        System.out.println(id);
        System.out.println("-------------");
//        2. 获取session创建时间
        long creationTime = session.getCreationTime();
        System.out.println(creationTime);
        System.out.println("-------------");
//        3. 获取最后一次访问时间
        long lastAccessedTime = session.getLastAccessedTime();
        System.out.println(lastAccessedTime);
        System.out.println("-------------");
//        4. 判断是否是新的session对象
        boolean aNew = session.isNew();
        System.out.println(aNew);
        ~~~

  // session 对象的存取
        session.setAttribute("xx","xx");
        Object xx = session.getAttribute("xx");

        // 1.设置session 的生命周期，时间为s，
        session.setMaxInactiveInterval(15);

//        2. 查看session最大时间周期
        int maxInactiveInterval = session.getMaxInactiveInterval();

//        3. 立即销毁
        session.invalidate();

//        4. 关闭浏览器

//        5. 关闭服务器

//        1. 直接通过request获取
        ServletContext servletContext1 = req.getServletContext();
//        2. 通过session获取
        ServletContext servletContext2 = req.getSession().getServletContext();
//        3. 直接获取
        ServletContext servletContext3 = req.getServletContext();
//        4. 通过servletConfig获取
        ServletContext servletContext4 = getServletConfig().getServletContext();

//        常用的两类方法：
//        1. 获取服务器版本信息
        ServletContext servletContext5 = req.getServletContext();
        String serverInfo = servletContext5.getServerInfo();

//        2. 获取项目真实路径
        String realPath = servletContext5.getRealPath("/");

        servletContext1.setAttribute("xx","xx");
        servletContext1.getAttribute("xx");
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