In the configuration files, especially servlet-context.xml, you will see the interceptor settings like this:
Spring Interceptors are used to intercept client requests and process them. Sometimes we want to intercept the HTTP Request and do some processing before handing it over to the controller handler methods.(Digital Ocean)
There are two ways to run interceptors: Inheriting abstract class HandlerInterceptorAdapter Class, or Inheriting interface HandlerInterceptor Interface.
Let's take a look at this LoginCheck.java.
LoginCheck.java
package com.ch.ch07;
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;
public class LoginCheck implements HandlerInterceptor {
public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
throws Exception {
}
public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
throws Exception {
}
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
HttpSession session = request.getSession();
if (session.getAttribute("id") == null) {
response.sendRedirect("loginForm.do");
return false;
}
return true;
}
}In this class, we are using the latter way. Here, we are only using preHandle method, which is needed between the Dispatcher Servlet class and the Controller class.
In the if statement in preHandle method, it will load to the loginForm if there is no session.
LoginForm.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ include file="header.jsp"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<div class="container">
<form action="login.do">
<h2 class="text-primary">Log In</h2>
<c:if test="${not empty msg }">
<span class="err">${msg }</span>
</c:if>
<table class="table table-bordered">
<tr>
<th>ID</th>
<td><input type="text" name="id" required="required"></td>
</tr>
<tr>
<th>Password</th>
<td><input type="password" name="pass" required="required"></td>
</tr>
<tr>
<th colspan="2"><input type="submit" value="확인"></th>
</tr>
</table>
</form>
</div>
</body>
</html>If you write the wrong ID or Password, it will load to @RequestMapping("login.do") and print out "Incorrect ID or Password."
UploadController.java
package com.ch.ch07;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.servlet.http.HttpSession;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
@Controller
public class UploadController {
@RequestMapping(value = "upload.do", method = RequestMethod.GET)
public String uploadForm() {
return "upload";
}
@RequestMapping(value = "upload.do", method = RequestMethod.POST)
public String upload(@RequestParam("file") MultipartFile mf, Model model, HttpSession session)
throws IllegalStateException, IOException {
String fileName = mf.getOriginalFilename();
int fileSize = (int) mf.getSize();
// mf.transferTo(new File("/gov/"+fileName));
String path = session.getServletContext().getRealPath("/upload");
FileOutputStream fos = new FileOutputStream(path + "/" + fileName);
fos.write(mf.getBytes());
fos.close();
model.addAttribute("fileName", fileName);
model.addAttribute("fileSize", fileSize);
return "uploadResult";
}
@RequestMapping("loginForm.do")
public String loginForm() {
return "loginForm";
}
@RequestMapping("login.do")
public String login(String id, String pass, HttpSession session, Model model) {
if (id.equals("java") && pass.equals("1234")) {
session.setAttribute("id", id);
return "loginSuccess";
} else {
model.addAttribute("msg", "Incorrect ID or Password");
return "loginForm";
}
}
}
When you write the correct ID and Password, you will see this.
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