Basic Web application creation Servlet / JSP (posting screen)

Introduction

This time, we will continue from the previous Basic Web application creation Servlet / JSP (login function). The aim of this article is to check whether you are logged in or not on the posting screen, and to handle the case when you are not.

Execution environment

• Eclipse4.16
• Tomcat9
• Java11

1. Create a model for a post

Since the posting screen is displayed, create a model of posting information. It is assumed that the user name and text exist in the post.

Article.java

public class Article implements Serializable{

	private String userName;
	private String text;

	Article(){}

	Article(String userName,String text){
		this.userName = userName;
		this.text = text;
	}

	public String getUserName() {
		return this.userName;
	}

	public String getText() {
		return this.text;
	}
}

2. Request processing controller for articles

Performs the process of confirming that you are logged in with this controller

--If you are logged in → Forward bulletin-board.jsp --If you are not logged in → Redirect to login screen

BulletinBoard.java

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		ServletContext application = this.getServletContext();
		List<Article> articleList = (List<Article>) application.getAttribute("articleList");  // 1
		if(articleList == null) {
			articleList = new ArrayList<Article>();
			application.setAttribute("articleList",articleList);  // 2
		}

		HttpSession session = request.getSession();
		User loginUser = (User) session.getAttribute("loginUser");  // 3

		if(loginUser == null) {
			response.sendRedirect("./login");  // 4
		}else {
			request.getRequestDispatcher("/WEB-INF/view/bulletin-board.jsp").forward(request, response);  // 5
		}
	}

1. Obtained from application scope
2. If 1 is null, set an empty article list in the application scope
3. Obtained from session scope
4. If you are not logged in, redirect to the login screen
5. If you are logged in, display the bulletin board screen

3. Create a view of the bulletin board screen

bulletin-board.jsp

<h2>This is the bulletin board screen.</h2>
<p><c:out value="${loginUser.name}"/>Is logged in.</p>

The second line prints who is logged in.

4. Run

If you check the operation and log in, the bulletin board screen will be displayed If you are not logged in, you will be successful if you are redirected to the login page! If you want to delete the session scope once, write the following

request.getSession().removeAttribute("loginUser");

Finally

Next time, we will implement the logout function.