Implementation:Ray project Ray Deployment Class Pattern

Knowledge Sources	Ray Ray Serve
Domains	Model_Serving, Microservices
Last Updated	2026-02-13 17:00 GMT

Overview

Interface specification for user-defined deployment handler classes in Ray Serve Java.

Description

Deployment classes are standard Java classes with a callable method (default name: call) that handles requests. The class is instantiated by RayServeReplicaImpl via ReflectUtil during replica startup. The constructor may accept configuration parameters.

Usage

Define a standard Java class with a call method. Register it via Serve.deployment().setDeploymentDef(className).bind().

Code Reference

Source Location

• Repository: ray-project/ray
• File: java/serve/src/test/java/io/ray/serve/docdemo/StrategyCalcOnRayServe.java (example)

Interface Specification

/**
 * Deployment class requirements:
 * 1. Public class accessible on the classpath
 * 2. Public no-arg or parameterized constructor
 * 3. Public method matching the callMethod name (default: "call")
 */
public class StrategyOnRayServe {
    private String prefix;

    public StrategyOnRayServe(String prefix) {
        this.prefix = prefix;
    }

    public String call(Object request) {
        return prefix + ": processed " + request.toString();
    }
}

Import

// No special imports for the class itself.
// Serve imports are needed when deploying:
import io.ray.serve.api.Serve;

I/O Contract

Inputs

Name	Type	Required	Description
request	Object	Yes	The request payload passed via DeploymentHandle.remote()

Outputs

Name	Type	Description
response	Object	The return value, sent back to the caller via DeploymentResponse

Usage Examples

Strategy Calculator Deployment

import io.ray.serve.api.Serve;
import io.ray.serve.deployment.Application;
import io.ray.serve.handle.DeploymentHandle;

public class ServeExample {
    // Deployment class
    public static class Calculator {
        public String call(Object input) {
            return "Result: " + input.toString();
        }
    }

    public static void main(String[] args) {
        Serve.start(new java.util.HashMap<>());

        Application app = Serve.deployment()
            .setName("calculator")
            .setDeploymentDef(Calculator.class.getName())
            .setNumReplicas(2)
            .bind();

        DeploymentHandle handle = Serve.run(app);
        Object result = handle.remote("42").result();
        System.out.println(result); // "Result: 42"

        Serve.shutdown();
    }
}

Related Pages

Implements Principle

• Principle:Ray_project_Ray_Deployment_Class_Definition

Requires Environment

• Environment:Ray_project_Ray_Java_Build_Environment