Spring Boot and Ratpack

With the advent of Ratpack and Spring Boot, many believe that you can only choose one. That couldn’t be further from the truth. The only area where they potentially overlap is in serving web requests. The Spring Framework is a very rich ecosystem including but not limited to DI, web mvc, data, security, etc. Ratpack focuses on rapid web app prototyping and iteration - balancing low resource utilization, high performance and developer friendliness. We’ll explore the ways in which Ratpack and Spring Boot work in harmony.

Spring Boot

Background

• Builds on 10+ Years of experience around Servlet based Web MVC applications

  • spring:spring-webmvc:1.0.2 published 2005

• Single self-contained artifact — standalone jar/war or war that can deploy to Servlet Container

• @Configuration encouraged although you can certainly define beans in XML

Figure 1. But why would you use XML over @Configuration

• Annotation-based framework integrations

  • spring-cloud projects

    • @EnableDiscoveryClient

    • @RibbonClient

Value

• Immediate impact for newcomers

• Industry standard

• Let’s user focus on writing business logic

Hello World

build.gradle

buildscript {
  ext {
    springBootVersion = '1.3.3.RELEASE'
  }
  repositories {
    mavenCentral()
  }
  dependencies {
    classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
  }
}

apply plugin: 'idea'
apply plugin: 'eclipse'
apply plugin: 'spring-boot'

repositories {
  jcenter()
  mavenCentral()
}

dependencies {
  compile('org.springframework.boot:spring-boot-starter-web')
}

SpringBootApp.java

package demo; // (1)

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@SpringBootApplication // (2)
@Controller // (3)
public class SpringBootApp {

  @RequestMapping("/")
  @ResponseBody String home() {
    return "Hello, World!";
  }

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

1. Doesn’t work if class is in default package

2. Activate Spring Boot web app

3. Spring MVC Controller Stereotype

$ ./gradlew bootRun

$ curl -v localhost:8080/
* timeout on name lookup is not supported
*   Trying ::1...
* Connected to localhost (::1) port 8080 (#0)
> GET / HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.45.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Server: Apache-Coyote/1.1
< Content-Type: text/plain;charset=UTF-8
< Content-Length: 13
< Date: Thu, 31 Mar 2016 03:27:03 GMT
<
Hello, World!* Connection #0 to host localhost left intact

Very compelling demo:

• No application-context.xml

• No web.xml

• No Tomcat configuration

Ratpack

Background

• Java 8+

• Builds on battle proven async/NIO networking framework — Netty

• Lightly opinionated (async/lazy/functional/immutable/composable/reactive)

• Lightweight && Low resource overhead → fast

• Collection of jars — no framework SDK / no codegen

• Not MVC

  • no controllers

  • no table routing

• Currently at 1.2.0 (Stable API)

Value

• WYSIWYG — no "magic" (no classpath scanning, no reflection)

• Start writing business logic immediately

• Designed for developer friendliness/productivity

• First class testing support

• Great for rapid prototyping and evolving to larger code base

• Reduce that monthly AWS bill $ $ $

Hello World Groovy

hello.groovy

@Grab('io.ratpack:ratpack-groovy:1.2.0')
import static ratpack.groovy.Groovy.ratpack

ratpack {
  handlers { // (1)
    get { // (2)
      render 'Hello, Groovy!'
    }
  }
}

1. Define request handling aspect of your application

2. Register a handler for GET / sends plain text response

$ groovy hello.groovy
$ curl -v localhost:5050/
* timeout on name lookup is not supported
*   Trying ::1...
* Connected to localhost (::1) port 5050 (#0)
> GET / HTTP/1.1
> Host: localhost:5050
> User-Agent: curl/7.45.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/plain;charset=UTF-8
< content-length: 14
< connection: keep-alive
<
Hello, Groovy!* Connection #0 to host localhost left intact

Handles "live reloads"

Hello World Java

build.gradle

plugins {
  id 'io.ratpack.ratpack-java' version '1.2.0'
  id 'com.github.johnrengelman.shadow' version '1.2.3'
}

mainClassName = 'RatpackApp'

repositories {
  jcenter()
}

RatpackApp.java

import ratpack.server.RatpackServer;

public class RatpackApp {
  public static void main(String[] args) throws Exception {
    RatpackServer.start(serverSpec -> serverSpec // (1)
      .handlers(chain -> chain // (2)
        .get(ctx -> ctx.getResponse().send("Hello, World!")) // (3)
      )
    );
  }
}

1. Supply specification on how to build the Ratpack application

2. Supply description of Ratpack application

3. Add handler for GET / endpoint

./gradlew run -t //(1)

1. Compile and run application in continuous mode (recompiles app as source changes)

$ curl -v localhost:5050
* Rebuilt URL to: localhost:5050/
* timeout on name lookup is not supported
*   Trying ::1...
* Connected to localhost (::1) port 5050 (#0)
> GET / HTTP/1.1
> Host: localhost:5050
> User-Agent: curl/7.45.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/plain;charset=UTF-8
< content-length: 13
< connection: keep-alive
<
Hello, World!* Connection #0 to host localhost left intact

Meet the API

The Handler

• SAM type

• Primary means of request processing

public interface Handler {
  void handle(Context context);
}

The Context

• Primary means of reading request and response object

• Primary means of inter Handler communciation

• Registry of application level and request level objects

• Provides easy access to features of Ratpack

  • Parsing

  • Rendering

  • HTTP objects

  • Execution

The Registry

A registry of objects of which Ratpack is aware; primarily used to communicate between Handler s.

RatpackRegistryApp.java

import ratpack.registry.Registry;
import ratpack.server.RatpackServer;

public class RatpackRegistryApp {
  public static void main(String[] args) throws Exception {
    RatpackServer.start(serverSpec -> serverSpec
      .registry(Registry.of(registrySpec -> registrySpec // (1)
        .add(MessageService.class, () -> "My message service") // (2)
      ))
      .handlers(chain -> chain
        .get(ctx -> {
          MessageService messageService = ctx.get(MessageService.class); // (3)
          ctx.render(messageService.send());
        })
      )
    );
  }
  interface MessageService {
    String send();
  }
}

1. Use Registry builder to build and add Registry to Ratpack server definition

2. Add an instance of MessageService to the Registry

3. Retrieve MessageService instance from Context Registry

$ curl -v localhost:5050/
* timeout on name lookup is not supported
*   Trying ::1...
* Connected to localhost (::1) port 5050 (#0)
> GET / HTTP/1.1
> Host: localhost:5050
> User-Agent: curl/7.45.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/plain;charset=UTF-8
< content-length: 18
< connection: keep-alive
<
My message service* Connection #0 to host localhost left intact

Communicating between handlers

RatpackRegistryApp.java

import ratpack.registry.Registry;
import ratpack.server.RatpackServer;

import java.time.Instant;

public class RatpackRegistryApp {
  public static void main(String[] args) throws Exception {
    RatpackServer.start(serverSpec -> serverSpec
      .registry(Registry.of(registrySpec -> registrySpec
        .add(MessageService.class, () -> "My message service")
      ))
      .handlers(chain -> chain
        .all(ctx -> // (1)
          ctx.next(Registry.single(Instant.now())) // (2)
        )
        .get(ctx -> {
          Instant requestStart = ctx.get(Instant.class); // (3)
          MessageService messageService = ctx.get(MessageService.class);
          ctx.render(requestStart + " " + messageService.send());
        })
      )
    );
  }
  interface MessageService {
    String send();
  }
}

1. Add handler that applies to every incoming request

2. Use Registry#single factory to create Registry of single item and pass to next qualifying handler

3. Retrieve Instant from created from upstream handler

$ curl -v localhost:5050
* Rebuilt URL to: localhost:5050/
* timeout on name lookup is not supported
*   Trying ::1...
* Connected to localhost (::1) port 5050 (#0)
> GET / HTTP/1.1
> Host: localhost:5050
> User-Agent: curl/7.45.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/plain;charset=UTF-8
< content-length: 43
< connection: keep-alive
<
2016-03-31T06:16:45.632Z My message service* Connection #0 to host localhost left intact

Integrating existing blocking libraries

RatpackBlockingIntegrationApp.java

import ratpack.exec.Blocking;
import ratpack.exec.Promise;
import ratpack.registry.Registry;
import ratpack.server.RatpackServer;

public class RatpackBlockingIntegrationApp {
  public static void main(String[] args) throws Exception {
    RatpackServer.start(serverSpec -> serverSpec
      .registry(Registry.of(registrySpec -> registrySpec
        .add(BlockingMessageService.class, () -> {
          try {
            Thread.sleep(1000); // (1)
          } catch (Exception e) {
            // uh oh
          }
          return "My blocking message service";
        })
      ))
      .handlers(chain -> chain
        .get(ctx -> {
          BlockingMessageService messageService = ctx.get(BlockingMessageService.class);
          Promise<String> promise = Blocking.get(messageService::send); (2)
          promise.then(ctx::render); (3)
        })
      )
    );
  }
  interface BlockingMessageService {
    String send();
  }
}

1. Simulate blocking behavior

2. Use Blocking#get(Factory) method to hook into Ratpack’s blocking executor

3. When promise is resolved send response to client

$ curl -v localhost:5050
* Rebuilt URL to: localhost:5050/
* timeout on name lookup is not supported
*   Trying ::1...
* Connected to localhost (::1) port 5050 (#0)
> GET / HTTP/1.1
> Host: localhost:5050
> User-Agent: curl/7.45.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/plain;charset=UTF-8
< content-length: 18
< connection: keep-alive
<
My blocking message service* Connection #0 to host localhost left intact

Spring and Ratpack Integration

Huge thanks to @dsyer (Dave Syer)

Ratpack Centric approach

build.gradle

plugins {
  id 'io.ratpack.ratpack-java' version '1.2.0'
  id 'com.github.johnrengelman.shadow' version '1.2.3' // (1)
}

mainClassName = 'RatpackApp' // (2)

repositories {
  jcenter()
}

dependencies {
  compile ratpack.dependency('spring-boot') // (3)
}

1. Shadow plugin to create fatjar

2. Specify main class

3. Add io.ratpack:ratpack-spring-boot:1.2.0 to compile time dependencies

RatpackApp.java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import ratpack.server.RatpackServer;
import ratpack.spring.Spring;

public class RatpackApp {
  public static void main(String[] args) throws Exception {
    RatpackServer.start(serverSpec -> serverSpec
      .registry(Spring.spring(MySpringConfig.class)) // (1)
      .handlers(chain -> chain
        .get(ctx -> {
          String hello = ctx.get(String.class); // (2)
          ctx.getResponse().send(hello);
        })
      )
    );
  }

  @Configuration
  public static class MySpringConfig {
    @Bean
    public String hello() {
      return "Hello from Spring!";
    }
  }
}

1. Add base Spring config class to Ratpack’s registry

2. Retrieves register Spring bean from Ratpack’s registry

Issuing a get request after starting the Ratpack application.

$ curl -v localhost:5050/
* timeout on name lookup is not supported
*   Trying ::1...
* Connected to localhost (::1) port 5050 (#0)
> GET / HTTP/1.1
> Host: localhost:5050
> User-Agent: curl/7.45.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/plain;charset=UTF-8
< content-length: 18
< connection: keep-alive
<
Hello from Spring!* Connection #0 to host localhost left intact

Spring Boot Centric approach

Spring Boot Initializr: Bootstrap Spring Boot

$ curl -o demo.zip "http://start.spring.io/starter.zip?type=gradle-project&bootVersion=1.3.3.RELEASE &baseDir=demo&groupId=com.example&artifactId=demo&name=demo&description=Demo+project+for+Spring+Boot &packageName=com.example&packaging=jar&javaVersion=1.8&language=java&autocomplete=&generate-project= &style=ratpack"

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 54752  100 54752    0     0   122k      0 --:--:-- --:--:-- --:--:--  126k

$ unzip -l demo.zip
Archive:  demo.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
        0  2016-03-31 02:41   demo/
     4957  2016-03-31 02:41   demo/gradlew
        0  2016-03-31 02:41   demo/gradle/
        0  2016-03-31 02:41   demo/gradle/wrapper/
        0  2016-03-31 02:41   demo/src/
        0  2016-03-31 02:41   demo/src/main/
        0  2016-03-31 02:41   demo/src/main/java/
        0  2016-03-31 02:41   demo/src/main/java/com/
        0  2016-03-31 02:41   demo/src/main/java/com/example/
        0  2016-03-31 02:41   demo/src/main/resources/
        0  2016-03-31 02:41   demo/src/test/
        0  2016-03-31 02:41   demo/src/test/java/
        0  2016-03-31 02:41   demo/src/test/java/com/
        0  2016-03-31 02:41   demo/src/test/java/com/example/
      891  2016-03-31 02:41   demo/build.gradle
    53638  2016-03-31 02:41   demo/gradle/wrapper/gradle-wrapper.jar
      200  2016-03-31 02:41   demo/gradle/wrapper/gradle-wrapper.properties
     2314  2016-03-31 02:41   demo/gradlew.bat
      299  2016-03-31 02:41   demo/src/main/java/com/example/DemoApplication.java
        0  2016-03-31 02:41   demo/src/main/resources/application.properties
      405  2016-03-31 02:41   demo/src/test/java/com/example/DemoApplicationTests.java
---------                     -------
    62704                     21 files

build.gradle

buildscript {
  ext {
    springBootVersion = '1.3.3.RELEASE'
  }
  repositories {
    mavenCentral()
  }
  dependencies {
    classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
  }
}

apply plugin: 'spring-boot'

repositories {
  jcenter()
  mavenCentral()
}

dependencies {
  compile project(':spring-config')
  compile('io.ratpack:ratpack-spring-boot:1.2.0')
  compile('org.springframework.boot:spring-boot-starter-web')
}

SpringBootCentricHelloWorld.java

package demo2;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import ratpack.func.Action;
import ratpack.handling.Chain;
import ratpack.spring.config.EnableRatpack;

@SpringBootApplication
@EnableRatpack // (1)
public class SpringBootCentricHelloWorld {

  @Bean
  Action<Chain> chain() { // (2)
    return chain -> chain
      .get(ctx -> ctx.render("Hello from Spring Boot!"));
  }

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

1. Configures Spring Boot to be Ratpack-aware

2. Provides the Action<Chain> as a Component, Spring takes care of building and starting Ratpack server

Note	Spring Boot (Spring MVC) and Ratpack will run side by side, binding to both 8080 (Tomcat default) and 5050 (Ratpack default). If you wish to disable Spring MVC autoconfig there are many ways to do so.

Defining controller and Ratpack handler chain side by side

SpringBootRatpackCommunicationApp.java

package demo3;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.client.RestTemplate;
import ratpack.func.Action;
import ratpack.handling.Chain;
import ratpack.http.client.HttpClient;
import ratpack.http.client.ReceivedResponse;
import ratpack.jackson.Jackson;
import ratpack.spring.config.EnableRatpack;

import java.net.URI;
import java.time.Instant;
import java.util.HashMap;
import java.util.Map;

@SpringBootApplication
@EnableRatpack
@Controller
public class SpringBootRatpackCommunicationApp {

  @Bean
  Action<Chain> chain() {
    return chain -> chain
      .get(ctx -> ctx.render("Hello from Ratpack in Spring Boot!"))
      .get("json", ctx -> { // (1)
        Map<String, String> map = new HashMap<>();
        map.put("date", Instant.now().toString());
        ctx.render(Jackson.json(map)); // (2)
      })
      .get("boot", ctx -> { // (3)
        HttpClient client = ctx.get(HttpClient.class); // (4)
        client.get(new URI("http://localhost:8080"))
          .map(ReceivedResponse::getBody)
          .map(body -> "Received from Spring Boot: " + body.getText())
          .then(ctx::render); // (5)
      });
  }

  @RequestMapping("/")
  @ResponseBody String bootRoot() {
    return "This is Spring Boot";
  }

  @RequestMapping("/ratpack")
  @ResponseBody Map bootRatpack() { // (6)
    RestTemplate restTemplate = new RestTemplate();
    return restTemplate.getForObject("http://localhost:5050/json", Map.class);
  }

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

1. Create GET /json endpoint in Ratpack chain that returns simple JSON object containing time of request

2. Utilize Jackson.json(Object) to create a renderable that knows how to send JSON to client.

3. Create GET /boot endpoint in Ratpack chain that sends a response based on response from Spring Boot app

4. Retrieve non-blocking/async HttpClient from Ratpack registry

5. Create GET / request against Spring Boot app, extract the response body and send to the user

6. Create GET /ratpack endpoing in Spring Boot app that issues a REST call against the previously defined /json endpoint in he Ratpack app and render the result to the user

$ curl localhost:8080
This is Spring Boot

$ curl localhost:5050
Hello from Ratpack in Spring Boot!

$ curl localhost:5050/boot
Received from Spring Boot: This is Spring Boot

$ curl localhost:8080/ratpack
{"date":"2016-03-31T07:11:14.178Z"}

compile 'io.ratpack:ratpack-spring-boot-starter:1.2.0'

Resources

• Spring Initializr

• Ratpack Homepage

• Ratpack source code

• Ratpack examples

• Ratpack user guide

• Ratpack Slack Registration

• Ratpack Forum

• Book: Learning Ratpack (O’Reilly)