How to set up Rocker templates with Maven?

Add the rocker-maven-plugin to your pom.xml and configure the template directory; the plugin automatically generates Java sources during the build phase, with detailed properties like templateDirectory and outputDirectory.

What's the performance difference between Rocker and FreeMarker?

According to the benchmark in the README, Rocker is about 250% faster than FreeMarker while using significantly less memory, due to its zero-copy rendering and lack of reflection.

How do I handle null values safely in Rocker templates?

Rocker provides a special '?' presence operator for null-safe evaluation, allowing concise handling of nullable variables without explicit Java null checks, as described in the syntax documentation.

Does Rocker work with Spring Boot?

While not explicitly listed, Rocker can be integrated with Spring Boot via its framework-agnostic design, but it may require custom configuration compared to supported frameworks like Micronaut.

Rocker or Thymeleaf for a new Java web app?

Rocker excels in performance and compile-time safety but has a steeper learning curve; Thymeleaf offers more familiar HTML-like syntax and broader community support but is slower and uses reflection.

How to enable hot reloading in Rocker during development?

Add the rocker-compiler dependency in provided scope and set the system property 'rocker.reloading=true' or programmatically via RockerRuntime, with two flavors offering trade-offs between type safety and flexibility.

Rocker — Java Template Engine

What is Rocker?

Rocker is a Java template engine that compiles HTML templates into statically typed Java classes during the build phase. It solves the problem of slow, reflection-based template engines by generating optimized Java code that runs with minimal memory overhead and no warm-up time.

Target Audience

Java developers building web applications or any system requiring dynamic HTML generation, especially those prioritizing performance, type safety, and seamless integration with existing Java tooling.

Value Proposition

Developers choose Rocker for its exceptional speed and memory efficiency due to zero-copy rendering, along with compile-time type safety that catches errors early and integrates naturally with IDEs.

Java 8 optimized, memory efficient, speedy template engine producing statically typed, plain java objects

Use Cases

Best For

High-traffic web applications needing efficient HTML rendering
Projects requiring compile-time validation of template logic and arguments
Developers wanting IDE support (code completion, refactoring) for templates
Microservices where low memory footprint and fast startup are critical
Teams using Java frameworks like Ninja, Jooby, Spark, or Micronaut
Applications needing hot reloading for templates during development

Not Ideal For

Projects requiring runtime template generation from dynamic sources like databases without rebuilds
Teams heavily invested in tag-based templating syntax like JSP or Thymeleaf for easier onboarding
Applications where minimal build configuration is a priority, preferring drop-in template engines without Maven/Gradle plugins
Environments needing GraalVM native image compatibility without switching to the STATIC_BYTE_ARRAYS plain text strategy

Pros & Cons

Pros

Zero-Copy Rendering

Reuses static byte arrays for template content, drastically reducing memory usage and CPU overhead by avoiding repeated conversions and copies, as highlighted in the performance benchmark.

Statically Typed Templates

Compiles templates into Java classes, enabling IDE support, compile-time checks, and easy debugging without runtime reflection, ensuring type safety from the start.

Flexible Hot Reloading

Offers two flavors of hot reloading during development, allowing rapid iteration without JVM restarts, though it requires additional setup with the rocker-compiler dependency.

Framework Integration

Seamlessly works with popular Java frameworks like Ninja, Jooby, Spark, and Micronaut, providing ready-to-use bindings for easier adoption in existing projects.

Cons

Build Tool Dependency

Requires integration with Maven or Gradle plugins for template compilation, adding complexity to the build configuration compared to simpler, runtime-only engines.

Syntax Learning Curve

Uses a tagless syntax with Java expressions, which may be unfamiliar to developers accustomed to HTML-like templating languages, potentially slowing initial adoption.

Limited Runtime Flexibility

Hot reloading's flavor two sacrifices compile-time type safety and incurs a performance penalty for dynamic interface support, as admitted in the README.

What is Rocker?

Target Audience

Java developers building web applications or any system requiring dynamic HTML generation, especially those prioritizing performance, type safety, and seamless integration with existing Java tooling.

Value Proposition

Developers choose Rocker for its exceptional speed and memory efficiency due to zero-copy rendering, along with compile-time type safety that catches errors early and integrates naturally with IDEs.

Use Cases

Best For

High-traffic web applications needing efficient HTML rendering
Projects requiring compile-time validation of template logic and arguments
Developers wanting IDE support (code completion, refactoring) for templates
Microservices where low memory footprint and fast startup are critical
Teams using Java frameworks like Ninja, Jooby, Spark, or Micronaut
Applications needing hot reloading for templates during development

Not Ideal For

Projects requiring runtime template generation from dynamic sources like databases without rebuilds
Teams heavily invested in tag-based templating syntax like JSP or Thymeleaf for easier onboarding
Applications where minimal build configuration is a priority, preferring drop-in template engines without Maven/Gradle plugins
Environments needing GraalVM native image compatibility without switching to the STATIC_BYTE_ARRAYS plain text strategy

Pros & Cons

Pros

Zero-Copy Rendering

Reuses static byte arrays for template content, drastically reducing memory usage and CPU overhead by avoiding repeated conversions and copies, as highlighted in the performance benchmark.

Statically Typed Templates

Compiles templates into Java classes, enabling IDE support, compile-time checks, and easy debugging without runtime reflection, ensuring type safety from the start.

Flexible Hot Reloading

Offers two flavors of hot reloading during development, allowing rapid iteration without JVM restarts, though it requires additional setup with the rocker-compiler dependency.

Framework Integration

Seamlessly works with popular Java frameworks like Ninja, Jooby, Spark, and Micronaut, providing ready-to-use bindings for easier adoption in existing projects.

Cons

Build Tool Dependency

Requires integration with Maven or Gradle plugins for template compilation, adding complexity to the build configuration compared to simpler, runtime-only engines.

Syntax Learning Curve

Uses a tagless syntax with Java expressions, which may be unfamiliar to developers accustomed to HTML-like templating languages, potentially slowing initial adoption.

Limited Runtime Flexibility

Hot reloading's flavor two sacrifices compile-time type safety and incurs a performance penalty for dynamic interface support, as admitted in the README.

Rocker

What is Rocker?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?

Rocker

What is Rocker?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?