JavaWeb零碎
2021/8/12 22:06:23
本文主要是介绍JavaWeb零碎,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
小七已经被JavaWeb折磨疯魔
JavaWeb零零碎碎的知识点实在是太多了,建了三四个项目,写了一堆demo,懒得整合了,打算重新写个新的,之前的就当做笔记挤在这里叭~
目前记录了:cookie, session, 打开新网页,转发,输出流,画图,重定向,和一个登录后端代码qwq
Cookie
添加cookie
public class demo2 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Cookie cookie = new Cookie("msg", "hello"); response.addCookie(cookie); } }
获取cookie
public class demo1 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Cookie[] cs = request.getCookies(); if (cs != null) { for (Cookie c : cs) { String name = c.getName(); String value = c.getValue(); System.out.println(name + ":" + value); } } } }
Session
public class demo1 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); session.setAttribute("msg", "hello"); } }
public class demo2 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); Object msg = session.getAttribute("msg"); System.out.println(msg); } }
乱七八糟小Demo
打开新路径
@WebServlet("/demo1") public class demo1 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //System.out.println("Demo1~"); String contextPath = request.getContextPath();//根路径 response.sendRedirect(contextPath + "/demo2");//打开demo2 } }
转发
@WebServlet("/demo2") public class demo2 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //System.out.println("Demo2222~"); request.getRequestDispatcher("/demo3").forward(request, response);//转发 } }
输出流
@WebServlet("/demo3") public class demo3 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //System.out.println("Demo3~"); response.setContentType("text/html;charset=utf-8"); //获取字节输出流 ServletOutputStream sos = response.getOutputStream(); sos.write("啊啊啊".getBytes("utf-8")); ServletContext context = this.getServletContext(); Object msg = context.getAttribute("msg"); System.out.println(msg); //获取字符输出流 response.setCharacterEncoding("utf-8"); //response.setHeader("content-type", "text/html;charset=utf-8"); PrintWriter pw = response.getWriter(); pw.write("<h1>咕咕咕啊啊啊aaaa</h1>"); } }
画图
@WebServlet("/demo4") public class demo4 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int width = 100; int height = 50; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); g.setColor(Color.PINK); g.fillRect(0, 0, width, height); g.setColor(Color.BLUE); g.drawRect(0, 0, width - 1, height - 1); String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZqwertyuiopasdfghjklzxcvbnm1234567890"; Random random = new Random(); for (int j = 1; j <= 4; ++j) { int i = random.nextInt(str.length()); char ch = str.charAt(i); g.drawString(ch + "", width / 5 * j, height / 2); } g.setColor(Color.GREEN); for (int i = 1; i <= 10; ++i) { int x1 = random.nextInt(width - 1); int x2 = random.nextInt(width - 1); int y1 = random.nextInt(height - 1); int y2 = random.nextInt(height - 1); g.drawLine(x1, y1, x2, y2); } ImageIO.write(image, "jpg", response.getOutputStream()); } }
登录验证码
<head> <meta charset="UTF-8"> <title>登录</title> <script> window.onload = function () { var img = document.getElementById("image"); img.onclick = function () { var date = new Date().getTime(); img.src = "/aaa/demo4?" + date; } } </script> </head> <body> <img id = "image" src="/aaa/demo4"/> <a id = "check" href="">看不清,换一张</a> </body>
重定向
@WebServlet("/resDemo") public class resDemo extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Demo1~"); response.setStatus(302); response.setHeader("location", "/reaDemo2"); } }
@WebServlet("/resDemo") public class resDemo2 extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Demo2~"); } }
登录
public class login extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws SecurityException, IOException { req.setCharacterEncoding("utf-8"); String name = req.getParameter("username"); String password = req.getParameter("password"); staff staff = new staff(); staff.setName(name); staff.setPassword(password); staffDao dao = new staffDao(); try { staff loginStaff = dao.login(staff); if (loginStaff == null) { req.getRequestDispatcher("/failLogin").forward(req, resp); } else { req.setAttribute("staff", staff); req.getRequestDispatcher("/successLogin").forward(req, resp); } } catch (SQLException | ServletException throwables) { throwables.printStackTrace(); } return; } }
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