Main points:
HttpSession: The establishment of a session starts with a user sending the first request to the server, and ends with an explicit end of the user or session timeout. With session, user status can be recorded in a certain time.
2.ModelAndView: You can either set the URL address or render the view.
3. Handler Interceptor: The interceptor interface can customize an interceptor by implementing three methods of interface modification (preHandle, postHandle, afterCompletion).
Examples:
Realize login and shopping cart functions.
login.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Lok login</title> </head> <body> <form action="http://localhost:8888/login-commit" method="post"> <input type="submit" value="login"> </form> </body> </html>
mall.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Le Tao shopping mall</title> </head> <body> <form action="http://localhost:8888/shopcar" method="POST"> <label>Please choose the books you want to buy:<br> <input type="checkbox" name="bookname" value="C Prime Plus">C Prime Plus<br> <input type="checkbox" name="bookname" value="C Prime Plus2">C Prime Plus2<br> <input type="checkbox" name="bookname" value="C Prime Plus3">C Prime Plus3<br> <input type="checkbox" name="bookname" value="C Prime Plus4">C Prime Plus4<br> </label> <input type="submit" value="Add to cart"> </form> <form action="http://localhost:8888/quit" method="POST"> <input value="log out" type="submit"> </form> </body> </html>
myshoppingcar.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Letao shopping cart</title> </head> <body> <h2>My shopping cart:</h2> <!--Show the purchased books when there is a purchase--> <ul th:if="${books.size()} != 0"> <li th:each="bookcount:${books}" th:text="${bookcount}"></li> </ul> <!--No purchase--> <div th:if="${books.size()} == 0"> You haven't bought any books! </div> <form action="http://localhost:8888/mall" method="GET"> <input type="submit" value="Continue to buy"> </form> </body> </html>
Books.java
package com.example.demo.controller.login; import java.util.HashMap; import java.util.Map.Entry; import java.util.Set; public class Books { private HashMap<String,Integer> books = new HashMap<String,Integer>(); //According to request URL Get an array of forms to update existing books public void refreshBooks(String[] newbooks) { for (String book:newbooks) { if (books.containsKey(book)) { books.put(book, books.get(book)+1); }else { books.put(book, 1); } } } //Obtain books Collection, to page public Set<Entry<String, Integer>> getbooks(){ return books.entrySet(); } }
LoginController.java
package com.example.demo.controller.login; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpSession; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PostMapping; @Controller public class LoginController { //Login interface @GetMapping("login") public String getLogin(HttpServletRequest req) { HttpSession session = req.getSession(); //Logged in and went directly to the mall if (session.getAttribute("login")!=null) { return "redirect:mall"; } return "login"; } //Logon request processing @PostMapping("login-commit") public String postLogin(HttpServletRequest req) { HttpSession session = req.getSession(); //session Mark logon status session.setAttribute("login",true); return "redirect:mall"; } //Log out and keep shopping records @PostMapping("quit") public String quit(HttpServletRequest req) { HttpSession session = req.getSession(); session.removeAttribute("login"); return "redirect:login"; } }
ShoppingController.java
package com.example.demo.controller.login; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpSession; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.servlet.ModelAndView; @Controller public class ShoppingController { //Market @GetMapping("mall") public String getMall() { return "mall"; } //My shopping cart @PostMapping("shopcar") public ModelAndView getShopCar(ModelAndView view,HttpServletRequest req) { HttpSession session = req.getSession(); Books books = (Books) session.getAttribute("shopcar");//session Conversational acquisition of purchased books String[] newbooks = req.getParameterValues("bookname");//New shopping requests //Never bought if (books==null){ books = new Books(); } //Refresh session Conversation if (newbooks!=null) { books.refreshBooks(newbooks); session.setAttribute("shopcar", books); } //Refresh model，Render view view.addObject("books",books.getbooks()); view.setViewName("myshoppingcar"); return view; } }
LoginInterceptor.java
package com.example.demo.controller.login; import java.io.IOException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView; //Logon interceptor public class LoginInterceptor implements HandlerInterceptor { @Override //stay Controller Call before method public boolean preHandle(HttpServletRequest req,HttpServletResponse res,Object handler) throws IOException { HttpSession session = req.getSession(); if (session.getAttribute("login") != null) { System.out.println("login!"); return true; } res.sendRedirect("login"); return false; } @Override public void postHandle(HttpServletRequest req,HttpServletResponse res,Object handler,ModelAndView modelandview) throws Exception { //Controller The method is finished, but html Called when the page is not displayed } @Override public void afterCompletion(HttpServletRequest req,HttpServletResponse res,Object handler,Exception ex) { //Called after the page is rendered, usually to reclaim resources, similar to finally } }
SpringWebConfig.java
package com.example.demo.controller.login; import org.springframework.boot.SpringBootConfiguration; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; @SpringBootConfiguration public class SpringWebConfig implements WebMvcConfigurer{ //Increase interceptors to specific URL Set Interception to Check Logon public void addInterceptors(InterceptorRegistry registry) { //Loading an interceptor,You can use wildcards, or string arrays registry.addInterceptor(new LoginInterceptor()).addPathPatterns("/mall","/quit"); } }