Overview of This Lesson

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Security is an important part of developing web applications. This lesson gives you an overview of important terms and concepts relating to web application security, and gives a quick demo of basic authentication in a Spring Boot application.

Resources Used in this Lesson

Reference Material

Security Overview and Background

I'm sure we don't need to go into great detail about why the security of your web application is so important: it's a subject you hear a lot about on the news and social media, especially when some big company gets hacked. But just in case you've been hiding in a cave for the last 20 years, the advent of computers, internet, and cloud storage have gradually made application/web security an issue over the years. When I first started working with computers, it wasn't a huge concern. There were some viruses but you could only get them if you used a computer disk that was from a "questionable" source. We weren't even downloading software back then because there was no where to download it from.

Eventually, the BBS (electronic Bulletin Board System) became popular: we could log into another computer (that was open and welcome to users, but only one person at a time could log in) and leave public and private messages for each other (again, this was before regular households had internet, so there was no MySpace or Facebook, this was a huge deal). Some of these BBS systems had file repositories where people could share files with each other. You had to be careful though, because some of those files might contain viruses!

Then the internet became popular with every-day computer users and now it was not only about viruses but also about hackers being able to access your own personal computer system via the internet and the data that was being transmitted. Then came online accounts and online shopping, and cloud computing and cloud storage, and with it the danger of your stored personal data being seen and copied and sold!

I've seen the issue of application and web security grow from something only people who weren't careful about where their programs came from to something we all have to worry about in our day-to-day life. In the past, if you took a disk from someone you didn't know very well or downloaded a file from a BBS, you ran the risk of getting a virus on your computer (and usually those viruses were more a nuisance or inconvenience than anything). But now, you could be doing your normal banking or shopping for groceries and have your entire livelihood compromised.

Web application security involves four major steps or components:

A user in the context of a secure application is a person using your application that has credentials. Credentials are the values the user uses to authenticate themselves, such as a username or email address and a password. A user of a secure application would typically have to provide their credentials in order to log in. For example, when you go to the SLATE home page, you are asked to log in with a form that asks for your Sheridan user name and password. Your user name and password are your credentials. When you provide your credentials and submit the form, the server authenticates you (assuming you've entered the correct credentials).

A role is just a name you make up for a particular group of users. For example, SLATE probably has roles for administrators, teachers, and students. Members of the administrator role maintain the SLATE system: they are the ones who set up our courses and run the scripts to add the students and teachers to each course. Members of the teachers role teach the courses and have permissions to add/edit/remove course objects like quizzes and content items, see student grades and activity data, etc. Members of the student role are enrolled in the course and have the ability to access all the course's objects that are made accessible by the teachers.

Another example: say you have a web application where people can purchase vinyl records you've collected. You might have an Admin role for users that are allowed to access pages used for adding/editing records in the collection and adding/editing customer accounts. You might also have a Manager role that is allowed to edit prices of records and create new promotions and discounts.

Users can be assigned to multiple roles. For example, all members of the teacher role are also enrolled in certain courses (like mandatory training courses from human resources on health & safety, diversity & inclusion, etc.) Therefore, members of the teacher role would also be members of the student role.

The things we are worried about the most (but not exclusively) in our web applications are:

We need to make sure our applications keep data secure and protect it from hackers.

Security in a Java Web App

In a Java web application you can restrict or constrain certain resources (pages, files, etc) by telling the server. It's actually a part of the server called the container (you might recall I mentioned the container before in the sessions lesson) that performs this task: the container has several jobs such as managing sessions, running Java code, and handling security and making sure that certain resources can only be accessed by certain people. Container-managed security requires users to identify themselves before allowing access to restricted resources. A typical conversation might take place as follows:

  1. The client requests a restricted resource.
    the client requests page.html
    The client requests a restricted page
  2. The Authentication process occurs:
    • The container sees that the requested resource is restricted, so it sends a response back to the browser asking for credentials.
      the server sends back a response, Who are you?
      The server response asks for credentials
    • The browser retrieves the credentials from the user (e.g. user name and password) and then sends a new request to the server with the credentials included.
      the client requests page.html and includes the username and password of the user
      The client requests a restricted page again but includes credentials
    • The container then examines the credentials and checks to see if they're valid.
  3. Then the Authorization process occurs:
    • If the credentials are valid, the container then checks to see if that user is allowed to access the restricted resources.
    • If the user is authorized, the container sends the requested resource(s) to the client.
      server checks to see if credentials are valid, yes, now checks to see if user can access page.html, yes, sends the page to the client in the response
      The server validates the user's credentials, then verifies that user is authorized to view the requested file

With Spring Boot, a lot of the security tasks are already set up and configured, you only need to customize the existing configuration to the security settings you want with the specific users and roles that you want.


Authentication is the process of determining who a user is by taking their credentials and matching them up with the users and roles that are allowed to access secure resources in the application. Information about users and roles and what resources are restricted are part of a security realm. This is just a way to store security information: how this is done depends on the kind of server (vendor).

There are four types of authentication you can use in a Java Web Application:

We'll focus on basic authentication in this lesson, then form authentication in the next lesson, and then client-certificate authentication in a later lesson. We won't be covering digest authentication since it's not used very much.


Authorization is the process of determining whether or not an authenticated user is permitted to access the resource that they requested. Authorization can't be performed if the user is not already authenticated, since you can only determine if someone is authorized to access a resource if you know they already have valid credentials.

Authorization is performed by setting security constraints on resources. Security constraints specify what users and/or roles are permitted to access a resource or set of resources. For example, you might specify that all users/roles are permitted to access everything in the /css and /scripts directory, but only admin users are permitted to access any file in the /inventory/management directory of the application.


Confidentiality and Data Integrity occur on a secure HTTP connection, or HTTPS. Secure HTTP (recall that HTTP stands for Hypertext Transfer Protocol) is the regular HTTP protocol with SSL or TLS on top of it. SSL (Secure Sockets Layer) and TLS (Transport Layer Security) are additional protocols that add a level of security to HTTP. We'll talk more about SSL and TLS in an upcoming lesson on how to use HTTPS.

HTTPS transmits data that is encrypted: the sender encrypts the data before its sent and the receiver decrypts it when the data is received. Special keys are used to encrypt and decrypt the data and only the sender and receiver know these keys. Therefore, an eavesdropper only sees the encrypted data being transmitted and can't do anything with it. This keeps the transmitted data confidential.

HTTPS is also able to determine if data was tampered with while being transmitted, with strengthens the data integrity.

HTTPS uses certificates to determine that the sender/receiver is who they say they are. When we get to the lesson on HTTPS, we'll be able to create "pretend" certificates so that we can test our applications on HTTPS.

Now that we have a general idea of some of the basic concepts, let's start implementing some of these things in a Spring Boot application.

Demonstration of Authentication in a Spring Boot App

We'll start off by creating a very basic application that introduces you to authentication. We'll talk more about authentication in later lessons when we also talk more about authorization and secure HTTP connections.

Creating a web application with authentication and authorization requires some extra components. We'll talk about the major ones we'll start with but I'll introduce a few more as we learn more in the next few lessons.

Spring Security Dependency

When you create a project, you'll need to include the Spring Security dependency. This dependency allows you to easily perform certain security tasks in your application such as configuration and setup of users, roles, and resource constraints. It also allows you to use several objects that are already created and set up by Spring and injected into the Inversion of Control container.

If you want to add Spring Security dependency to an exsting project, just add the following two items to your POM file's dependencies:


This dependency allows you to perform certain security operations in your Thymeleaf pages, such as accessing the name of the currently logged in user.

If you see this dependency, then you're fine and don't have to worry about it. If you don't see this dependency, you'll have to add it manually in the POM for each project you create from now on if you want to use Spring Security in your Thymeleaf pages (obviously if you're not using any of the security operations in your Thymeleaf pages, there's no point in adding this dependency).

A SecurityConfig Class

A security config class defines various settings for your application such as how you want to encrypt passwords, what roles/users you want to use (or where the security realm data is stored), where the login page is (if you created your own), what resources are restricted to which users/roles, etc.

The Security Config class always goes into the .security package of your application.

public class SecurityConfig {


The Security Config class is annotated with the @EnableWebSecurity annotation, which is in the org.springframework.security.config.annotation.web.configuration package. This annotation switches off the default web application security configuration set by Spring so you can add custom features. This is achieved by adding one or more configuration methods that set the properties and preferences you want.

One of the greatest things about a security config class annotated with @EnableWebSecurity is that it automatically prevents Cross-Site Request Forgery and Session Fixation attacks.

SecurityWebApplicationInitializer Class

The Security Web Application Initializer creates a filter chain. Every request that goes to the server for your application is filtered to make sure it meets your authentication requirements. A filter is an object that the request has to travel "through" on its way to the application: A filter reads the request and the request data and can perform actions based on the data it sees. For example, if a request doesn't contain authentication credentials, the filter can send a redirect, causing the request to change to a login.html page instead of the page it was originally requesting. The initializer uses your security config class to determine how authentication should work for the requests so that it knows what to do when the requests are filtered.

This class is generally very basic and is always stored in your application's root package along with the main Application class.

public class SecurityWebApplicationInitializer extends AbstractSecurityWebApplicationInitializer {

    public SecurityWebApplicationInitializer() {

The class extends AbstractSecurityWebApplicationInitializer. I know these class names are getting really long, but that's quite normal: remember that class names need to be self documenting! AbstractSecurityWebApplicationInitializer is the abstract class that models the filter chain for a secure web application. We extend it to create our own version so that we can configure it with the settings we are going to define in the Security Config class mentioned in the previous section.


Start a new project and add dependencies for Spring Web, Dev Tools, Lombok, Thymeleaf, and Spring Security. Make sure the "thymeleaf extras" appears in the POM, and if not, add it.

SecurityConfig Class

Add a new class called SecurityConfig to a .security package in your application. This class should be annotated with @EnableWebSecurity as described earlier.

We'll start off with something really basic. Add a method to the SecurityConfig class and Autowire it:

configureGlobal method, message me if you require accessible version
A configureGlobal() method in the SecurityConfig class

The actual method name "configureGlobal()" doesn't actually matter: you can use any method name here but it must be self-documenting and conform to other rules and industry standards. I chose the name "configureGlobal" because it configures the security options for the entire application.

There are several classes and methods used here that we haven't seen before:

What's really nice is that all this will automatically prevent CSRF and session fixation attacks - it's all built-in!

SecurityWebApplicationInitializer class

Now go into the root package of your project, where your Application class is (we looked at this class in our very first project, in case you aren't sure or can't remember) and add the SecurityWebApplicationInitializer that extends the AbstractSecurityWebApplicationInitializer class. I showed you the code for this class earlier, in case you want to copy and paste it.

NOTE: when prompted to import the SecurityConfig class, make sure you import your own SecurityConfig, not one of the other ones!

Index Page

Now add an index.html page to your /templates. Add the regular thymeleaf namespace, but you'll also need to add an extra name space that allows us to use the thymeleaf sec tags:

<html xmlns:th="http://www.thymeleaf.org" 

Inside the body of the page, add a heading (e.g. Testing Spring Security) and a DIV element:

<div sec:authorize="isAuthenticated()"></div>

Here, we use the sec:authorize attribute that's part of the Thymeleaf "security extras". It will render the element its a part of ONLY if the expression it is assigned is true (therefore, it must be assigned a boolean expression). The isAuthenticated() method (and you don't have to include the () when you write that in Thymeleaf, but you probably figured that out already) is from the Authentication interface, which models the authentication information for an authenticated user. It contains a few other methods you might find useful in a Thymeleaf page, and we'll explore some of this in this lesson and in future lessons. The isAuthenticated() method returns true if the user is authenticated, and false if they're not authenticated.

Therefore, our DIV element is only rendered if the user that requested this page is currently authenticated. If they are not authenticated, this element is not rendered at all. We want to display a bit of information about the authenticated user, so let's put some code inside the DIV to display it:

<div sec:authorize="isAuthenticated()">
<p>User Name: <span sec:authentication="name"></span>
Roles: <span sec:authentication="principal.authorities"></span>

The sec:authentication attribute displays specific content from the current authenticated user. For example, sec:authentication="name" invokes the Authentication.getName() method (getName() is actually inherited from java.security.Principal), which returns the name of this user (e.g. "Foo") as a String.

The sec:authentication="principal.authorities" invokes the getPrincipal() method and retrieves the roles.

A "Principal" is simply any kind of entity with a name, and it's used often in authentication to model the person/thing being authenticated.

So this DIV contains code that displays the name of the user and the roles the user belongs to, but only if the user is authenticated, otherwise it displays nothing (except the header at the top, if you added one)

Note that I didn't put in fallback code for our SPAN elements: the user wont see any of this if they're not authenticated, so it doesn't matter that much. Also note that even though we might often want to display the name of the currently authenticated user, we will probably never display the roles the user belongs to (except maybe in a back-end administrative interface you created) - we only do it here for demonstration purposes and to show you what you can do, and so you'll be intrigued enough to explore more on your own.

We'll add one last cool thing to this page before we try it all out. Add a small form with a single "Log Out" button. This code should go inside the DIV and below the paragraph element that displays the authentication data:

<form method="get" action="#" th:action="@{/logout}">
<input type="submit" value="Log Out">

I'm using the th:action and setting action="#" because I want the form to be processed by the handler method only when Thymeleaf is working/active.

To do the actual logging out functionality, you only need a handler method mapped to /logout - as long as you use "/logout" - this is built-in and the application will perform a log out automatically! Furthermore:

Add a controller to the .controllers package. Add two handler methods:

Recall from the controllers and mappings lesson that you can use the same mapping as long as the methods are different.

Add a third handler that loads the index page when the user goes to http://localhost:8080/.

Now run your application like you normally would and load your index page. You should see a form that asks for credentials, although it might not look exactly like mine (I'm using Chrome):

basic form with username and password fields and a Sign In button
The default login form in Chrome

The reason you see the form is because we set up security constraints for ALL files in our application: this means we can't access *anything* in our project unless we meet the criteria (we must be authenticated as the user "Foo").

The HTML for this form is created by Spring Boot, but in a later lesson I'll show you how you can create and customize your own login form. Have a look at the form's source code: look at the code for the form and its input fields. We'll find this interesting in an upcoming lesson, so take some time to examine it and how it's all created.

When you're done examining the form source code, enter credentials that are incorrect and see what happens.

basic form with Bad credentials error message and blank fields
Error appears if the credentials aren't valid

Notice that the message only says "bad credentials" - there is no mention of whether it was the login or password that was incorrect, nor does it fill the form with the values that the user entered previously, or display those values anywhere. This is exactly what should happen. NEVER give a potential hacker any help: if you say the login name is in valid or the password is invalid, you're giving them way too much information. If they know the user name is valid but they messed up the password, they're halfway to breaking into the account.

Now try the valid credentials you set in the configureGlobal() method. You should now see the index page with the user name and role you defined, because the DIV's sec:authorize="isAuthenticated()" is now true.

the index page with the user name, role, and the logout button
Using valid credentials shows the user information

Click the Log Out button. Since we're using the GET method on our log out form, we recieve a confirmation first:

confirmation: are you sure you want to log out? followed by log out button
GET method on the form triggers confirmation

Go ahead and click the Log Out button on the confirmation screen. The login form appears again because you are now logged out and trying to access the index page.

Is there a way to display certain content to authenticated users and different content for non-authenticated users? Yes! We'll learn this in an upcoming lesson.

Go to your index page and change the form method to POST, and then try the program again. Notice that when you log out, you don't get the confirmation screen.

Those are the basics! In the next lesson we'll do a bit more: we'll create our own custom login form, and we'll refine our security configuration to allow access to some parts of our application but not others.


Add a new Thymeleaf page called yourname.html where "yourname" is your Sheridan user name. On your page, add a HEADER element that is only visible to authenticated users. It should display a level-1 heading that says, "Welcome " followed by the name of the currently authenticated user. Add a handler method to your controller that loads the page (the mapping should be /yourname where "yourname" is your Sheridan user name.

Add another user to your security config. The user should have your Sheridan login name, a role of "STUDENT", and a made-up password (DO NOT use your actual password!) You can do this with the and() method chained to the previous user methods and then attach another set of methods to the and():

code to add a second user
GET method on the form triggers confirmation

Save your changes and make sure you're logged out before you refresh the browser, or restart your application, after saving your changes. Load the page with your name on it, log in, etc. Test it all out, including the index page.