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Spring Security is a powerful and highly customizable authentication and access-control framework for Java applications. It is the de-facto standard for securing Spring-based applications. In this section, we will cover the basics of Spring Security, its core concepts, and how to integrate it into a Spring Boot application.

Key Concepts

Authentication: The process of verifying the identity of a user or system.
Authorization: The process of determining whether an authenticated user has the necessary permissions to perform a specific action.
Principal: The currently authenticated user.
Granted Authority: A permission or role assigned to a principal.
Security Context: Holds the security information of the current user, including authentication and granted authorities.

Why Use Spring Security?

Comprehensive Security: Provides a wide range of security features, including authentication, authorization, and protection against common attacks (e.g., CSRF, XSS).
Integration: Seamlessly integrates with Spring applications.
Customization: Highly customizable to meet specific security requirements.
Community Support: Backed by a large community and extensive documentation.

Setting Up Spring Security in a Spring Boot Application

Step 1: Add Spring Security Dependency

First, add the Spring Security dependency to your pom.xml file:

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

Step 2: Configure Spring Security

Create a configuration class to set up Spring Security. This class should extend WebSecurityConfigurerAdapter and override the necessary methods.

import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .authorizeRequests()
                .anyRequest().authenticated()
                .and()
            .formLogin()
                .and()
            .httpBasic();
    }
}

Explanation

@Configuration: Indicates that this class contains Spring configuration.
@EnableWebSecurity: Enables Spring Security’s web security support.
authorizeRequests(): Configures authorization for HTTP requests.
anyRequest().authenticated(): Requires authentication for any request.
formLogin(): Enables form-based login.
httpBasic(): Enables HTTP Basic authentication.

Step 3: Run the Application

Run your Spring Boot application. By default, Spring Security will secure all endpoints and provide a default login page. The default username is user, and the password is generated at runtime and printed in the console.

Practical Example

Let's create a simple Spring Boot application with a secured endpoint.

Step 1: Create a Spring Boot Application

Use Spring Initializr to create a new Spring Boot project with the following dependencies:

Spring Web
Spring Security

Step 2: Create a Controller

Create a simple REST controller with a secured endpoint.

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello, World!";
    }
}

Step 3: Configure Security

Create the SecurityConfig class as shown earlier.

Step 4: Run the Application

Run the application and navigate to http://localhost:8080/hello. You will be prompted to log in. Use the default credentials (user and the generated password) to access the endpoint.

Exercises

Exercise 1: Custom Login Page

Modify the SecurityConfig class to use a custom login page.

@Override
protected void configure(HttpSecurity http) throws Exception {
    http
        .authorizeRequests()
            .anyRequest().authenticated()
            .and()
        .formLogin()
            .loginPage("/login")
            .permitAll()
            .and()
        .httpBasic();
}

Create a simple login page (src/main/resources/templates/login.html):

<!DOCTYPE html>
<html>
<head>
    <title>Login</title>
</head>
<body>
    <h1>Login</h1>
    <form method="post" action="/login">
        <div>
            <label>Username:</label>
            <input type="text" name="username"/>
        </div>
        <div>
            <label>Password:</label>
            <input type="password" name="password"/>
        </div>
        <div>
            <button type="submit">Login</button>
        </div>
    </form>
</body>
</html>

Solution

Update the SecurityConfig class as shown above.
Create the login.html file in the templates directory.

Exercise 2: Role-Based Authorization

Modify the SecurityConfig class to restrict access to the /admin endpoint to users with the ADMIN role.

@Override
protected void configure(HttpSecurity http) throws Exception {
    http
        .authorizeRequests()
            .antMatchers("/admin").hasRole("ADMIN")
            .anyRequest().authenticated()
            .and()
        .formLogin()
            .permitAll()
            .and()
        .httpBasic();
}

Create a new controller with an /admin endpoint.

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AdminController {

    @GetMapping("/admin")
    public String admin() {
        return "Admin Page";
    }
}

Solution

Update the SecurityConfig class as shown above.
Create the AdminController class with the /admin endpoint.

Summary

In this section, we introduced Spring Security and its core concepts. We demonstrated how to set up Spring Security in a Spring Boot application, configure basic authentication, and create a custom login page. We also provided practical exercises to reinforce the learned concepts. In the next section, we will delve deeper into configuring Spring Security and implementing user authentication and authorization.

Introduction to Spring Security

Key Concepts

Why Use Spring Security?

Setting Up Spring Security in a Spring Boot Application

Step 1: Add Spring Security Dependency

Step 2: Configure Spring Security

Explanation

Step 3: Run the Application

Practical Example

Step 1: Create a Spring Boot Application

Step 2: Create a Controller

Step 3: Configure Security

Step 4: Run the Application

Exercises

Exercise 1: Custom Login Page

Solution

Exercise 2: Role-Based Authorization

Solution

Summary

Spring Boot Course

Module 1: Introduction to Spring Boot

Module 2: Spring Boot Basics

Module 3: Building RESTful Web Services

Module 4: Data Access with Spring Boot

Module 5: Spring Boot Security

Module 6: Testing in Spring Boot

Module 7: Advanced Spring Boot Features

Module 8: Deploying Spring Boot Applications

Module 9: Performance and Monitoring

Module 10: Best Practices and Tips