Why Choose Juneau?

Apache Juneau™ offers a unique combination of simplicity, power, and zero-dependency design that makes it an excellent choice for modern Java development. Here's why developers choose Juneau over alternatives.

The Juneau Advantage

Zero Dependencies, Maximum Power

Unlike other frameworks that require multiple dependencies and complex configurations, Juneau provides comprehensive functionality with minimal external requirements:

Juneau:

<dependency>
    <groupId>org.apache.juneau</groupId>
    <artifactId>juneau-all</artifactId>
    <version>9.1.0</version>
</dependency>

Alternative (Spring Boot + Jackson + Swagger):

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
</dependency>
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger2</artifactId>
</dependency>
<!-- Plus many more dependencies -->

Unified API, Multiple Formats

Juneau provides a single, consistent API for serializing to multiple formats:

// One API, multiple formats
Person person = new Person("John", 30);

// JSON
String json = JsonSerializer.DEFAULT.serialize(person);

// XML  
String xml = XmlSerializer.DEFAULT.serialize(person);

// HTML
String html = HtmlSerializer.DEFAULT.serialize(person);

// URL-Encoding
String urlEnc = UrlEncodingSerializer.DEFAULT.serialize(person);

With alternatives, you need different libraries and APIs for each format.

Self-Documenting REST APIs

Juneau automatically generates Swagger documentation from your POJOs and annotations:

@Rest(title="User API", description="User management service")
public class UserResource extends BasicRestServlet {
    
    @RestGet("/users/{id}")
    public User getUser(@Path String id) {
        return userService.findById(id);
    }
    
    @RestPost("/users")
    public User createUser(@Body User user) {
        return userService.create(user);
    }
}

Result: Automatic Swagger UI at /swagger-ui.html with full API documentation, request/response schemas, and interactive testing.

Type-Safe REST Client Proxies

Create type-safe client interfaces that feel like local method calls:

@Remote("http://api.example.com")
public interface UserService {
    @Get("/users/{id}")
    User getUser(@Path String id);
    
    @Post("/users")
    User createUser(@Body User user);
}

// Use like a regular Java interface
UserService service = RestClient.create().build().getRemote(UserService.class);
User user = service.getUser("123");

No more manual HTTP client code, JSON parsing, or error handling.

Serverless Testing

Test REST APIs without starting servers or containers:

@Test
public void testUserAPI() throws Exception {
    String response = MockRestClient
        .create(UserResource.class)
        .json5()
        .build()
        .get("/users/123")
        .run()
        .assertStatus().is(200)
        .getContent().asString();
    
    assertThat(response).contains("John");
}

Fast, reliable tests that don't require external dependencies.

Comparison with Popular Alternatives

vs. Jackson

Feature	Juneau	Jackson
Formats Supported	JSON, XML, HTML, URL-Encoding, UON, OpenAPI, PlainText, CSV, SOAP, MessagePack, RDF	JSON only
REST API Support	Built-in with automatic Swagger	Requires additional frameworks
Configuration	Zero configuration	Requires setup and configuration
Testing Support	Built-in MockRestClient	Requires external testing tools
Dependencies	Self-contained	Requires additional libraries for other formats

Juneau Advantage: Single library for multiple formats + REST APIs + testing, while Jackson only handles JSON serialization.

vs. Spring Boot Web Controllers

Feature	Juneau	Spring Boot
Content Negotiation	Automatic for all formats	Manual setup required
API Documentation	Automatic Swagger generation	Requires additional configuration
Testing	Built-in MockRestClient	Requires @WebMvcTest or TestContainers
Dependencies	Minimal	Heavy framework with many dependencies
Learning Curve	Simple POJO-based approach	Complex annotation system

Juneau Advantage: Simpler, more focused approach with built-in features that require additional setup in Spring Boot.

vs. JAX-RS

Feature	Juneau	JAX-RS
Implementation	Single implementation	Multiple competing implementations
Content Negotiation	Automatic	Manual configuration
Documentation	Automatic Swagger	Requires additional tools
Testing	Built-in support	Requires external testing frameworks
Dependencies	Self-contained	Requires implementation + additional libraries

Juneau Advantage: Complete solution vs. specification that requires multiple libraries and configuration.

Real-World Benefits

Enterprise Development

• Reduced Complexity: Fewer dependencies mean fewer security vulnerabilities and maintenance overhead
• Faster Onboarding: New developers can be productive immediately with intuitive POJO-based APIs
• Consistent APIs: Same patterns across serialization, REST services, and testing
• Built-in Documentation: Automatic Swagger generation reduces documentation maintenance

Microservices

• Lightweight: Minimal memory footprint and fast startup times
• Self-Contained: No external dependencies to manage in containers
• Flexible Deployment: Works with any Servlet 3.1+ container or embedded Jetty
• Easy Testing: MockRestClient enables comprehensive testing without external services

API Development

• Rapid Prototyping: Create working APIs in minutes, not hours
• Automatic Documentation: Swagger UI generated automatically from your code
• Content Negotiation: Support multiple formats with zero additional configuration
• Type Safety: Compile-time checking for REST client interfaces

When to Choose Juneau

Perfect For:

• Multi-format APIs: When you need to support JSON, XML, HTML, and other formats
• Rapid Development: When you want to build APIs quickly without complex configuration
• Microservices: When you need lightweight, self-contained services
• Testing: When you want comprehensive testing without external dependencies
• Documentation: When you need automatic API documentation generation
• Learning: When you want to understand REST APIs without framework complexity

Consider Alternatives If:

• Heavy Spring Ecosystem: You're already deeply invested in Spring Boot's ecosystem
• Complex Enterprise Features: You need advanced enterprise features like distributed transactions
• Large Team: Your team has extensive experience with other frameworks
• Legacy Integration: You need to integrate with existing Spring-based systems

Getting Started

Ready to try Juneau? Here's how to get started:

1. Add Dependency

<dependency>
    <groupId>org.apache.juneau</groupId>
    <artifactId>juneau-all</artifactId>
    <version>9.1.0</version>
</dependency>

2. Create Your First API

@Rest(title="My API")
public class HelloResource extends BasicRestServlet {
    
    @RestGet("/hello/{name}")
    public String sayHello(@Path String name) {
        return "Hello " + name + "!";
    }
}

3. Deploy and Test

// Deploy to any Servlet container or use embedded Jetty
// Automatic Swagger UI available at /swagger-ui.html
// Test with MockRestClient

Community and Support

• Documentation: Comprehensive guides and examples at juneau.staged.apache.org
• Examples: Working code examples in the juneau-examples repository
• Community: Join discussions on the Apache Juneau mailing list
• Issues: Report bugs and request features on GitHub Issues

Conclusion

Juneau offers a compelling alternative to complex, multi-library solutions. By providing a unified API for serialization, REST services, and testing with minimal dependencies, Juneau enables developers to focus on business logic rather than framework configuration.

Try Juneau today and experience the simplicity of zero-dependency Java development.

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Still not convinced? Check out our Framework Comparisons page for detailed technical comparisons, or explore our comprehensive examples to see Juneau in action.