javaweb基础（一）

 @WebServlet("/demo2")//访问demo2目录会创建此servlet
 @WebServlet({"/demo2","/demo3"})//访问demo2或demo3会创建此servlet
 @WebServlet("/demo4/demo3")//访问demo4/demo3会创建此servlet
 @WebServlet("/demo4/*")//访问demo4下的所有会创建此servlet
 @WebServlet("/demo4/*.do")//访问demo4下的所有有.do后缀会创建此servlet
 public class ServletDemo2 implements Servlet {
     @Override
     public void init(ServletConfig servletConfig) throws ServletException {
     }
     @Override
     public ServletConfig getServletConfig() {
         return null;
     }
     @Override
     public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
         System.out.println("------------------");
     }
     @Override
     public String getServletInfo() {
         return null;
     }
     @Override
     public void destroy() {
     }
 }

 @Target({ElementType.TYPE})
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 public @interface WebServlet {
     String name() default "";//相当于<Servlet-name>
     String[] value() default {};//代表urlPatterns()属性配置
     String[] urlPatterns() default {};//相当于<url-pattern>
     int loadOnStartup() default -1;//相当于<load-on-startup>
     WebInitParam[] initParams() default {};
     boolean asyncSupported() default false;
     String smallIcon() default "";
     String largeIcon() default "";
     String description() default "";
     String displayName() default "";
 }

 @WebServlet("/demo3")
 public class ServletDemo3 extends HttpServlet {
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         System.out.println("doPost");
     }
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         System.out.println("doGet");
     }
 }

 POST /login.html    HTTP/1.1
 Host: localhost
 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0
 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
 Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
 Accept-Encoding: gzip, deflate
 Referer: http://localhost/login.html
 Connection: keep-alive
 Upgrade-Insecure-Requests: 1
 
 username=zhangsan

@WebServlet("/demo3")
 public class ServletDemo3 extends HttpServlet {
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         System.out.println("doPost");
     }
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         String method = req.getMethod();
         String contextPath = req.getContextPath();
         String servletPath = req.getServletPath();
         String queryString = req.getQueryString();
         String requestURI = req.getRequestURI();
         StringBuffer requestURL = req.getRequestURL();
         String protocol = req.getProtocol();
         String remoteAddr = req.getRemoteAddr();
         System.out.println("请求方式："+method);
         System.out.println("虚拟目录："+contextPath);
         System.out.println("Servlet路径："+servletPath);
         System.out.println("get方式请求参数："+queryString);
         System.out.println("URI："+requestURI);
         System.out.println("URL："+requestURL);
         System.out.println("协议及版本："+protocol);
         System.out.println("客户机的IP地址："+remoteAddr);
     }
 }

 GET
 WebTomcat_war
 demo3
 null
 WebTomcat_war/demo3
 http://localhost:8080/WebTomcat_war/demo3
 HTTP/1.1
 0:0:0:0:0:0:0:1

     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         Enumeration<String> headerNames = req.getHeaderNames();
         while (headerNames.hasMoreElements()) {
             String s = headerNames.nextElement();
             String header = req.getHeader(s);
             System.out.println(s + "  :  " + header);
         }
 
         String agent = req.getHeader("user-agent");
         if (agent.contains("Chrome")) {
             System.out.println("你使用的是谷歌浏览器");
         } else if (agent.contains("edge")) {
             System.out.println("你使用的是edge浏览器");
         }
     }

 host  :  localhost:8080
 connection  :  keep-alive
 upgrade-insecure-requests  :  1
 user-agent  :  Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36 Edg/87.0.664.75
 accept  :  text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
 sec-fetch-site  :  none
 sec-fetch-mode  :  navigate
 sec-fetch-user  :  ?1
 sec-fetch-dest  :  document
 accept-encoding  :  gzip, deflate, br
 accept-language  :  zh-CN,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6
 cookie  :  JSESSIONID=C981EFE2E9E19533C612212F2457FD5B; Phpstorm-20f921f5=e75a0f7d-9766-4502-8af8-465f6ed9632f; _ga=GA1.1.72471488.1606467110; user_device_id_timestamp=1606487566478; Hm_lvt_fdafb975c7b15a614fe2dd7716c44e87=1606467111,1606487567

     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         BufferedReader reader = req.getReader();
         String line;
         while ((line = reader.readLine()) != null) {
             System.out.println(line);
         }
     }

  @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         req.setCharacterEncoding("utf-8");
         String username = req.getParameter("username");
 
         Enumeration<String> parameterNames = req.getParameterNames();
 
 //        while(parameterNames.hasMoreElements()){
 //            String name=parameterNames.nextElement();
 //            System.out.print(name);
 //            String value = req.getParameter(name);
 //            System.out.print(" ---- ");
 //            System.out.println(value);
 //        }
 
         Map<String, String[]> parameterMap = req.getParameterMap();
         for(String name: parameterMap.keySet()){
             String[] values=parameterMap.get(name);
             System.out.println(name);
             Arrays.stream(values).forEach(System.out::print);
             System.out.println("---");
         }
     }

 username
 20185655---
 password
 12343212---
 hobby
 singdancerap---

 @WebServlet("/demo7")
 public class ServletDemo7 extends HttpServlet {
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         System.out.println("demo7");
         req.getRequestDispatcher("/demo8").forward(req, resp);
     }
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         this.doPost(req, resp);
     }
 }
 
 @WebServlet("/demo8")
 public class ServletDemo8 extends HttpServlet {
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp)  {
         System.out.println("demo8");
 
     }
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
         this.doPost(req,resp);
     }
 }

 demo7
 demo8

 @WebServlet("/demo7")
 public class ServletDemo7 extends HttpServlet {
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         req.setAttribute("name", "wenwen");
         System.out.println("demo7");
         req.getRequestDispatcher("/demo8").forward(req, resp);
     }
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         this.doPost(req, resp);
     }
 }
 @WebServlet("/demo8")
 public class ServletDemo8 extends HttpServlet {
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
 
         Object name = req.getAttribute("name");
         System.out.println(name);
         System.out.println("demo8");
 
     }
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
         this.doPost(req, resp);
     }
 }

 demo7
 wenwen
 demo8

 ServletContext servletContext = req.getServletContext();
 System.out.println(servletContext);

 org.apache.catalina.core.ApplicationContextFacade@64e82ff