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README.adoc

This guide walks you through the process of creating a simple web application with resources that are protected by Spring Security.

What You Will Build

You will build a Spring MVC application that secures the page with a login form that is backed by a fixed list of users.

Starting with Spring Initializr

For all Spring applications, you should start with the Spring Initializr. The Initializr offers a fast way to pull in all the dependencies you need for an application and does a lot of the setup for you. This example needs the Spring Web and Thymeleaf dependencies.

The following listing shows the pom.xml file that is created when you choose Maven:

link:initial/pom.xml[]

The following listing shows the build.gradle file that is created when you choose Gradle:

link:initial/build.gradle[]

Create an Unsecured Web Application

Before you can apply security to a web application, you need a web application to secure. This section walks you through creating a simple web application. Then you will secure it with Spring Security in the next section.

The web application includes two simple views: a home page and a “Hello, World” page. The home page is defined in the following Thymeleaf template (from src/main/resources/templates/home.html):

link:initial/src/main/resources/templates/home.html[]

This simple view includes a link to the /hello page, which is defined in the following Thymeleaf template (from src/main/resources/templates/hello.html):

link:initial/src/main/resources/templates/hello.html[]

The web application is based on Spring MVC. As a result, you need to configure Spring MVC and set up view controllers to expose these templates. The following listing (from src/main/java/com/example/securingweb/MvcConfig.java) shows a class that configures Spring MVC in the application:

link:initial/src/main/java/com/example/securingweb/MvcConfig.java[]

The addViewControllers() method (which overrides the method of the same name in WebMvcConfigurer) adds four view controllers. Two of the view controllers reference the view whose name is home (defined in home.html), and another references the view named hello (defined in hello.html). The fourth view controller references another view named login. You will create that view in the next section.

At this point, you could jump ahead to “Run the Application” and run the application without having to log in to anything.

Now that you have an unsecured web application, you can add security to it.

Set up Spring Security

Suppose that you want to prevent unauthorized users from viewing the greeting page at /hello. As it is now, if visitors click the link on the home page, they see the greeting with no barriers to stop them. You need to add a barrier that forces the visitor to sign in before they can see that page.

You do that by configuring Spring Security in the application. If Spring Security is on the classpath, Spring Boot automatically secures all HTTP endpoints with “basic” authentication. However, you can further customize the security settings. The first thing you need to do is add Spring Security to the classpath.

With Gradle, you need to add two lines (one for the application and one for testing) in the dependencies closure in build.gradle, as the following listing shows:

implementation 'org.springframework.boot:spring-boot-starter-security'
implementation 'org.springframework.security:spring-security-test'

The following listing shows the finished build.gradle file:

link:complete/build.gradle[]

With Maven, you need to add two extra entries (one for the application and one for testing) to the <dependencies> element in pom.xml, as the following listing shows:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
  <groupId>org.springframework.security</groupId>
  <artifactId>spring-security-test</artifactId>
  <scope>test</scope>
</dependency>

The following listing shows the finished pom.xml file:

link:complete/pom.xml[]

The following security configuration (from src/main/java/com/example/securingweb/WebSecurityConfig.java) ensures that only authenticated users can see the secret greeting:

link:complete/src/main/java/com/example/securingweb/WebSecurityConfig.java[]

The WebSecurityConfig class is annotated with @EnableWebSecurity to enable Spring Security’s web security support and provide the Spring MVC integration. It also extends WebSecurityConfigurerAdapter and overrides a couple of its methods to set some specifics of the web security configuration.

The configure(HttpSecurity) method defines which URL paths should be secured and which should not. Specifically, the / and /home paths are configured to not require any authentication. All other paths must be authenticated.

When a user successfully logs in, they are redirected to the previously requested page that required authentication. There is a custom /login page (which is specified by loginPage()), and everyone is allowed to view it.

The userDetailsService() method sets up an in-memory user store with a single user. That user is given a user name of user, a password of password, and a role of USER.

Now you need to create the login page. There is already a view controller for the login view, so you need only to create the login view itself, as the following listing (from src/main/resources/templates/login.html) shows:

link:complete/src/main/resources/templates/login.html[]

This Thymeleaf template presents a form that captures a username and password and posts them to /login. As configured, Spring Security provides a filter that intercepts that request and authenticates the user. If the user fails to authenticate, the page is redirected to /login?error, and your page displays the appropriate error message. Upon successfully signing out, your application is sent to /login?logout, and your page displays the appropriate success message.

Last, you need to provide the visitor a way to display the current user name and sign out. To do so, update the hello.html to say hello to the current user and contain a Sign Out form, as the following listing (from src/main/resources/templates/hello.html) shows:

link:complete/src/main/resources/templates/hello.html[]

We display the username by using Spring Security’s integration with HttpServletRequest#getRemoteUser(). The “Sign Out” form submits a POST to /logout. Upon successfully logging out, it redirects the user to /login?logout.

Run the Application

The Spring Initializr creates an application class for you. In this case, you need not modify the class. The following listing (from src/main/java/com/example/securingweb/SecuringWebApplication.java) shows the application class:

link:complete/src/main/java/com/example/securingweb/SecuringWebApplication.java[]

Once the application starts up, point your browser to http://localhost:8080. You should see the home page, as the following image shows:

The application’s home page

When you click on the link, it attempts to take you to the greeting page at /hello. However, because that page is secured and you have not yet logged in, it takes you to the login page, as the following image shows:

The login page
Note
If you jumped down here with the unsecured version, you do not see the login page. You should back up and write the rest of the security-based code.

At the login page, sign in as the test user by entering user and password for the username and password fields, respectively. Once you submit the login form, you are authenticated and then taken to the greeting page, as the following image shows:

The secured greeting page

If you click on the Sign Out button, your authentication is revoked, and you are returned to the login page with a message indicating that you are logged out.

Summary

Congratulations! You have developed a simple web application that is secured with Spring Security.

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Securing a Web Application :: Learn how to protect your web application with Spring Security.

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