spring boot之http，页面状态跳转与异常处理实战

Http使用

　　http的使用主要是三个类:HttpServletRequest(向客户端取数据),HttpServletResponse(向客户端发数据),HttpSession(记录浏览器和服务器的长期交互)。

HttpServletRequest

　　取出http的请求头的参数和cookie数据：

    @RequestMapping(path= {"/request"})
    @ResponseBody
    public String request(HttpServletRequest request,
                                    HttpServletResponse response,
                                    HttpSession session) {
        StringBuilder sb = new StringBuilder();
        Enumeration<String> headerNames = request.getHeaderNames();
        while(headerNames.hasMoreElements()) {
            String name = headerNames.nextElement();
            sb.append(name + " ::::::::::::::::::::::::::::: " + request.getHeader(name) + "<br/>");
        }
        for (Cookie cookie : request.getCookies()) {
            sb.append("Cookie: ");
            sb.append(cookie.getName());
            sb.append(":");
            sb.append(cookie.getValue());
            sb.append("<br>");
        }
        return sb.toString();
    }

　　显示结果：

HttpServletResponse

　　添加cookie并在页面上显示：

    @RequestMapping(value= {"/response"})
    @ResponseBody
    public String response( @CookieValue(value = "cookieid", defaultValue = "cookieId") String cookieId,
                            @RequestParam(value = "key", defaultValue = "key") String key,
                            @RequestParam(value = "value", defaultValue = "value") String value,
                            HttpServletResponse response) {
        response.addCookie(new Cookie(key, value));
        //response.addHeader(key, value);
        return "cookievalue: " + cookieId;
    }

 显示结果：

　　备注：在url中把key写入cookieid，显示时，cookieid就会显示value值，随value的改变而改变。

301，302页面跳转与HttpSession

　　若访问/redirect/301，就永久跳转到/hello下(301)，不经过判断。否则暂时性跳转(302)。

　　 //301永久性跳转
    //302暂时性跳转
    @RequestMapping(path = {"/redirect/{code}"})
    @ResponseBody
        public RedirectView redirect(@PathVariable("code") int code,
                                     HttpSession session) {
        RedirectView red = new RedirectView("/hello", true);
        if (code == 301)
            red.setStatusCode(HttpStatus.MOVED_PERMANENTLY);//301跳转
        //session，记录浏览器和服务器长期的交互。
        session.setAttribute("msg", "jump from redirect");
        return red;
    }

　　其次，/hello路径：

    @RequestMapping(path = {"/hello"})
    @ResponseBody
    public String Hello_World(Model model,
                              HttpSession session) {
        model.addAttribute("aaa", "naive");
        model.addAttribute("l", "<br/>");
        List<String> ls = Arrays.asList(new String[] {"1","111", "2323a"});
        model.addAttribute("liststring", ls);
        model.addAttribute("user", new User("aw12"));
        logger.info("yeah,finally i learn how to use logger");
        //显示session的msg信息。
        return "session" + session.getAttribute("msg") + sss.show();
    }

　　

异常及异常处理

　　当key的值不是admin时，抛出异常，在exception函数中处理异常。

//异常
    @RequestMapping(path = {"/admin"})
    @ResponseBody
    public String error(@RequestParam(value = "key", required = false) String key) {
        if ("admin".equals(key))
            return "hello admin";
        throw new IllegalArgumentException("Key 错误");
    }
    //处理异常
    @ExceptionHandler
    @ResponseBody
    public String exception(Exception e) {
        return "error" + e.getMessage();
    }

　　结果一，key=‘admin"时：

　　

　　结果二，key！="admin"时：