Pros of Spring Boot

• Extensive ecosystem and community support
• Comprehensive documentation and learning resources
• Wide range of production-ready starters and auto-configuration options

Cons of Spring Boot

• Larger memory footprint and slower startup times
• Heavier reliance on runtime reflection
• Steeper learning curve for beginners

Code Comparison

Spring Boot:

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Micronaut:

@Singleton
public class Application {
    public static void main(String[] args) {
        Micronaut.run(Application.class, args);
    }
}

Both frameworks offer similar syntax for bootstrapping applications, but Micronaut's approach is more lightweight and doesn't rely on runtime reflection. Spring Boot's @SpringBootApplication annotation combines multiple annotations, while Micronaut uses a simpler @Singleton annotation.

Spring Boot's extensive ecosystem and mature documentation make it a popular choice for enterprise applications. However, Micronaut's focus on reducing memory usage and startup times makes it more suitable for microservices and serverless environments.

Pros of Quarkus

• Faster startup time and lower memory footprint
• Better native image support with GraalVM
• More extensive Kubernetes and cloud-native features

Cons of Quarkus

• Steeper learning curve for developers new to reactive programming
• Smaller ecosystem and community compared to Micronaut
• Less flexible in terms of customization options

Code Comparison

Quarkus:

@Path("/hello")
public class GreetingResource {
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return "Hello from Quarkus";
    }
}

Micronaut:

@Controller("/hello")
public class GreetingController {
    @Get(produces = MediaType.TEXT_PLAIN)
    public String hello() {
        return "Hello from Micronaut";
    }
}

Both frameworks use similar annotations for defining RESTful endpoints, but Quarkus uses JAX-RS annotations while Micronaut uses its own set of annotations. The overall structure and simplicity of the code are comparable, making it easy for developers to switch between the two frameworks.

Pros of Vert.x

• Highly scalable and performant, designed for handling concurrent connections
• More flexible and lightweight, allowing for fine-grained control
• Supports multiple programming languages (polyglot)

Cons of Vert.x

• Steeper learning curve, especially for developers new to reactive programming
• Less opinionated, requiring more manual configuration and setup
• Smaller ecosystem compared to Micronaut

Code Comparison

Vert.x HTTP server:

Vertx vertx = Vertx.vertx();
vertx.createHttpServer().requestHandler(req -> {
  req.response().end("Hello World!");
}).listen(8080);

Micronaut HTTP server:

@Controller("/")
public class HelloController {
    @Get
    public String index() {
        return "Hello World!";
    }
}

Vert.x focuses on a more low-level, event-driven approach, while Micronaut provides a higher-level, annotation-based programming model. Vert.x offers more flexibility but requires more boilerplate code, whereas Micronaut simplifies common tasks with its opinionated design.

Pros of Javalin

• Lightweight and simple, with a minimal learning curve
• Fast startup time and low memory footprint
• Excellent for microservices and small to medium-sized applications

Cons of Javalin

• Limited built-in features compared to Micronaut's extensive ecosystem
• Less suitable for large, complex enterprise applications
• Fewer integrations with other frameworks and libraries out of the box

Code Comparison

Javalin:

import io.javalin.Javalin;

public class HelloWorld {
    public static void main(String[] args) {
        Javalin app = Javalin.create().start(7000);
        app.get("/", ctx -> ctx.result("Hello World"));
    }
}

Micronaut:

import io.micronaut.http.annotation.*;
import io.micronaut.http.client.annotation.*;
import io.micronaut.runtime.Micronaut;

@Controller("/")
public class HelloController {
    @Get
    public String index() {
        return "Hello World";
    }

    public static void main(String[] args) {
        Micronaut.run(HelloController.class);
    }
}

Pros of Helidon

• Built and maintained by Oracle, providing enterprise-level support and integration with Oracle Cloud
• Offers both a lightweight microframework (Helidon SE) and a full MicroProfile implementation (Helidon MP)
• Strong focus on reactive programming and non-blocking I/O

Cons of Helidon

• Smaller community and ecosystem compared to Micronaut
• Less extensive documentation and fewer third-party integrations
• Steeper learning curve for developers new to reactive programming concepts

Code Comparison

Helidon (Reactive WebServer):

Routing.builder()
    .get("/greet", (req, res) -> res.send("Hello, World!"))
    .build();
WebServer.create(routing).start();

Micronaut (HTTP Server):

@Controller("/greet")
public class GreetingController {
    @Get
    public String greet() {
        return "Hello, World!";
    }
}

Both frameworks offer concise ways to create web endpoints, but Helidon's approach is more focused on reactive programming, while Micronaut provides a more traditional annotation-based controller style.

Pros of Dropwizard

• Mature and battle-tested framework with a large community
• Excellent documentation and extensive examples
• Integrates well-established libraries like Jetty and Jersey

Cons of Dropwizard

• Heavier footprint and slower startup times
• Less flexible for microservices architecture
• Limited support for reactive programming

Code Comparison

Dropwizard:

public class HelloWorldApplication extends Application<HelloWorldConfiguration> {
    public static void main(String[] args) throws Exception {
        new HelloWorldApplication().run(args);
    }
}

Micronaut:

@Singleton
public class HelloController {
    @Get("/hello")
    public String hello() {
        return "Hello World";
    }
}

Dropwizard follows a more traditional Java application structure with a main class extending Application, while Micronaut uses annotations and dependency injection for a more concise setup. Micronaut's approach is generally more suitable for microservices and serverless environments, offering faster startup times and lower memory footprint. However, Dropwizard's mature ecosystem and comprehensive documentation make it a solid choice for larger, more complex applications where performance at scale is less critical than developer productivity and established patterns.