Reference: Bridges

Installation (Gradle)

dependencies {
    
    implementation(platform("org.http4k:http4k-bom:6.1.0.1"))

    // Helidon: 
    implementation("org.http4k:http4k-bridge-helidon")
    
    // Servlet (Jakarta):
    implementation("org.http4k:http4k-bridge-jakarta")
    
    // Ktor: 
    implementation("org.http4k:http4k-bridge-ktor")
    
    // Micronaut: 
    implementation("org.http4k:http4k-bridge-micronaut")
    
    // Ratpack: 
    implementation("org.http4k:http4k-bridge-ratpack")
    
    // Servlet (javax): 
    implementation("org.http4k:http4k-bridge-servlet")

    // Spring: 
    implementation("org.http4k:http4k-bridge-spring")
    
    // Vertx: 
    implementation("org.http4k:http4k-bridge-vertx")
}

Bridge modules provide a layer of integration with other web frameworks, allowing http4k applications to be deployed alongside them.

The integration allows teams to incrementally introduce http4k into existing applications, creating a path of migration from other migrations to http4k.

We currently provide bridges for the following frameworks:

• Spring (see migration example)
• Ktor (see migration example)
• Micronaut (see migration example)
• Helidon
• Vertx
• Ratpack
• Servlet (jakarta and javax)

General migration strategy

1. Add the bridge module for the framework you are using.
2. Create a “fallback” HttpHandler as starting point for the migration.
3. Use the bridge to route requests to the fallback handler when no other routes are found.
4. Recreate a particular route in http4k, and remove it from the framework when it is ready.
5. Repeat step 4 until all routes are migrated.
6. Change the application entry point to serve from the http4k HttpHandler rather than the framework.
7. Remove the bridge module and other usages of the framework.