Pros of CAS

• More flexible and customizable architecture
• Stronger support for higher education institutions
• Extensive plugin ecosystem for additional features

Cons of CAS

• Steeper learning curve and more complex configuration
• Less out-of-the-box features compared to Keycloak
• Smaller community and fewer resources available

Code Comparison

CAS (Java):

@Bean
public ServiceRegistryDao serviceRegistryDao() {
    return new InMemoryServiceRegistry();
}

Keycloak (Java):

@Singleton
public class CustomAuthenticator implements Authenticator {
    @Override
    public void authenticate(AuthenticationFlowContext context) {
        // Custom authentication logic
    }
}

Both projects use Java, but CAS tends to rely more on Spring Framework conventions, while Keycloak uses a more custom approach. CAS configuration often involves Spring beans, whereas Keycloak typically uses SPI interfaces for customization.

CAS offers more flexibility in terms of service registry implementation, allowing for easy swapping between different storage options. Keycloak, on the other hand, provides a more standardized approach to extending authentication flows through its SPI system.

Overall, CAS is more adaptable but requires more effort to set up, while Keycloak offers a more streamlined experience with less initial customization options.

Pros of Spring Security

• Tightly integrated with Spring ecosystem, offering seamless compatibility with Spring Boot and other Spring projects
• Highly customizable and flexible, allowing developers to implement complex security scenarios
• Extensive documentation and large community support

Cons of Spring Security

• Steeper learning curve, especially for developers new to Spring framework
• Can be complex to configure for advanced use cases
• Requires more manual setup compared to Keycloak's out-of-the-box features

Code Comparison

Spring Security configuration example:

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests()
            .antMatchers("/public/**").permitAll()
            .anyRequest().authenticated()
            .and().formLogin();
    }
}

Keycloak configuration example:

@Configuration
public class KeycloakConfig {
    @Bean
    public KeycloakConfigResolver keycloakConfigResolver() {
        return new KeycloakSpringBootConfigResolver();
    }
}

The Spring Security example shows a more detailed configuration, while Keycloak's setup is simpler due to its pre-configured nature. Spring Security offers more granular control, but Keycloak provides a more streamlined approach for standard authentication scenarios.

Pros of Hydra

• Lightweight and highly performant, designed for high-scale environments
• Flexible and easily integrable into existing systems
• Strong focus on OAuth 2.0 and OpenID Connect standards compliance

Cons of Hydra

• Less comprehensive out-of-the-box features compared to Keycloak
• Steeper learning curve for initial setup and configuration
• Smaller community and ecosystem compared to Keycloak

Code Comparison

Hydra (Go):

import "github.com/ory/hydra/client"

c := client.NewHTTPClientWithConfig(nil, &client.TransportConfig{
    Schemes:  []string{"http", "https"},
    Host:     "localhost:4444",
    BasePath: "/",
})

Keycloak (Java):

import org.keycloak.admin.client.Keycloak;

Keycloak keycloak = Keycloak.getInstance(
    "http://localhost:8080/auth",
    "master",
    "admin",
    "password",
    "admin-cli");

Both examples show client initialization, but Hydra's approach is more focused on HTTP transport configuration, while Keycloak's includes authentication details for the admin client.

Pros of SuperTokens

• Lightweight and focused on core authentication functionality
• Easy to integrate with modern web and mobile applications
• Extensive documentation and developer-friendly API

Cons of SuperTokens

• Less mature and smaller community compared to Keycloak
• Fewer built-in features and integrations out of the box
• Limited enterprise-level support options

Code Comparison

SuperTokens:

import SuperTokens from "supertokens-node";
import Session from "supertokens-node/recipe/session";

SuperTokens.init({
    appInfo: { apiDomain: "...", appName: "..." },
    recipeList: [Session.init()]
});

Keycloak:

import org.keycloak.adapters.KeycloakConfigResolver;
import org.keycloak.adapters.springboot.KeycloakSpringBootConfigResolver;

@Configuration
public class KeycloakConfig {
    @Bean
    public KeycloakConfigResolver keycloakConfigResolver() {
        return new KeycloakSpringBootConfigResolver();
    }
}

The code snippets demonstrate the initialization process for both libraries. SuperTokens uses a more straightforward JavaScript-based configuration, while Keycloak requires Java-based setup with Spring Boot integration.

Pros of NextAuth.js

• Lightweight and easy to integrate with Next.js applications
• Supports a wide range of authentication providers out-of-the-box
• Simpler setup and configuration for basic authentication needs

Cons of NextAuth.js

• Limited advanced features compared to Keycloak's enterprise-grade offerings
• Less suitable for complex, multi-tenant authentication scenarios
• Fewer built-in security features and compliance certifications

Code Comparison

NextAuth.js:

import NextAuth from "next-auth"
import Providers from "next-auth/providers"

export default NextAuth({
  providers: [
    Providers.Google({
      clientId: process.env.GOOGLE_ID,
      clientSecret: process.env.GOOGLE_SECRET
    }),
  ],
})

Keycloak:

KeycloakBuilder keycloak = KeycloakBuilder.builder()
    .serverUrl("https://keycloak-server/auth")
    .realm("myrealm")
    .clientId("myclient")
    .clientSecret("client-secret")
    .build();

AccessTokenResponse response = keycloak.tokenManager().grantToken();
String token = response.getToken();

NextAuth.js is more focused on simplicity and ease of use, particularly for Next.js applications. It offers a straightforward setup process and supports various authentication providers. However, it may lack some advanced features and enterprise-grade capabilities that Keycloak provides.

Keycloak, on the other hand, offers a more comprehensive authentication and authorization solution, suitable for complex scenarios and enterprise environments. It provides advanced security features, multi-tenancy support, and extensive customization options, but may require more setup and configuration compared to NextAuth.js.