Introduction

Spring Boot and JSON Web Tokens (JWT) together provide a robust solution for token-based authentication. JWT is a compact, URL-safe means of representing claims to be transferred between two parties. In this guide, we'll explore how to implement token-based authentication with JWT in a Spring Boot application, understand how it works, and provide sample code with explanations for its implementation.

Understanding JWT-Based Authentication

JWT is a self-contained token that can securely transmit information between parties as a JSON object. It is commonly used for authentication and authorization in web applications. JWTs consist of three parts: a header, payload, and signature. They are typically used as bearer tokens, which are included in the request headers for authentication.

Key Components of JWT-Based Authentication

Implementing JWT-based authentication in Spring Boot involves the following key components:

• JWT Library: Include a JWT library, such as jjwt, to handle JWT generation and parsing.
• Security Configuration: Configure security rules in your Spring Boot application to validate JWTs and authenticate users.
• Authentication Filter: Implement a custom authentication filter to extract and verify JWTs from incoming requests.
• User Details Service: Define a user details service to load user information from your data source.

Implementing JWT-Based Authentication

To implement token-based authentication with JWT in Spring Boot, follow these steps:

1. Add the necessary dependencies to your project's pom.xml (Maven) or build.gradle (Gradle) file:

<!-- Maven -->
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.9.1</version>
</dependency>
        

// Gradle
dependencies {
    implementation 'io.jsonwebtoken:jjwt:0.9.1'
}
        

2. Create a class that defines your JWT security configuration:

import org.springframework.context.annotation.Bean;
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.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.crypto.factory.PasswordEncoderFactories;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;
@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .addFilterBefore(new JwtAuthenticationFilter(), UsernamePasswordAuthenticationFilter.class)
            .authorizeRequests()
                .antMatchers("/public/**").permitAll()
                .anyRequest().authenticated()
                .and()
            .csrf().disable();
    }
    @Bean
    @Override
    public UserDetailsService userDetailsService() {
        PasswordEncoder encoder = PasswordEncoderFactories.createDelegatingPasswordEncoder();
        UserDetails user = User.builder()
            .username("user")
            .password(encoder.encode("password"))
            .roles("USER")
            .build();
        return new InMemoryUserDetailsManager(user);
    }
}
        

In this example, we configure a basic security setup where URLs under "/public" are accessible without authentication, and all other URLs require authentication with a JWT token. You can replace the user details service and add JWT token handling as needed.

Conclusion

Implementing token-based authentication with JWT in Spring Boot is a secure and efficient way to protect your applications and APIs. This guide introduced JWT-based authentication, its components, and provided sample code for its implementation. As you further explore token-based authentication, you'll find that it's a powerful solution for securing your Spring Boot applications.