1.
http://www.ratpack.io
Dan Woods
#ratpack #learningratpack

2.
• Member of the Ratpack core team
• Work at Netflix
• Writing Learning Ratpack for O’Reilly
• Follow me on Twitter: @danveloper

3.
• A full-stack, high throughput, non-blocking
web framework
• Built entirely on Java 8
• Specialized support for writing apps in Groovy

4.
• Groovy has come a long way over the last few
years…
• Static compilation and (optional) compile time type
checking
• Excellent language for writing concise DSLs
• DSLs can be statically compiled!
Why Groovy?

5.
• Groovy’s three compilation modes give
applications a lot of flexibility
• Parallels Java performance using Invoke Dynamic
or Static Compilation
• Pick-and-choose static or dynamic, depending on
the use-case!
Why Groovy?

6.
• Requires Groovy 2.3.6+
• Utilize advanced static compilation and type
checking features of Groovy, like @DelegatesTo
• Allows you to define your application structure in a
ratpack.groovy file
Why Groovy?

7.
@GrabResolver(name='netty', root='http://clinker.netty.io/
nexus/content/repositories/snapshots')!
@Grab('io.ratpack:ratpack-groovy:0.9.13-SNAPSHOT')!
!
import static ratpack.groovy.Groovy.ratpack!
!
ratpack {!
handlers {!
handler { !
response.send ”Hello World!"!
}!
}!
}!
Simple Groovy Script*
* @GrabResolver will not be required after 4.1.0-Beta4 is published;
* Ratpack 0.9.13 will be released on Feb 1, 2014

8.
• There are no plugins in Ratpack, instead the
framework provides functionality through modules
• Modules are built in Guice*
• DI is an abstraction in Ratpack, so even though the
framework uses Guice, you don’t have to
*
h$ps://github.com/google/guice

9.
• A set of composable libraries for building
unopinionated, rich web applications
• Pick-and-choose what aspects of the
framework you want
• No lock-in to a single way of doing things

10.
• Emphasis on Performance and Efficiency in both applications
and development experience
• Hot reloading is available during development time
• Beautiful development-time error pages
• Extreme emphasis on developer testing, especially functional
and integration
• Support for mocking nearly all aspects of the framework

11.
Example of a development-time error:

12.
• Convention over configuration taken too far
doesn’t let you wire things together
• Ratpack makes wiring modules a “one-liner”, so
there’s not a lot of work to get new features
integrated
• Out of the box support for Guice and Spring
(Spring Boot) DI

13.
• Gradle integration makes building robust
projects easy to do
• Simple apps can be run entirely through
the Groovy command-line

14.
buildscript {
repositories {
jcenter()
maven { url "http://oss.jfrog.org/oss-snapshot-local" }
maven { url "http://clinker.netty.io/nexus/content/repositories/snapshots" }
}
dependencies {
classpath 'io.ratpack:ratpack-gradle:0.9.13-SNAPSHOT'
}
}
apply plugin: 'io.ratpack.ratpack-java'
Simple Gradle Build Script*
* Ratpack 0.9.13 will be released on Feb 1, 2014

15.
• Any non-trivial application needs build and
packaging capabilities
• The Ratpack Gradle plugin provides all the
fixtures to support building web
application projects

16.
• Ratpack is built on Netty, which provides
the infrastructure for highly performant,
non-blocking networking

17.
• Netty is an extremely mature, super low-level
networking library
• Excellent documentation, very involved
community
• Heavy emphasis on high throughput and
performance

18.
• Netty provides the infrastructure for non-
blocking networking, but doesn’t help
much in the way of web application
structure
• Provides an asynchronous API for working
with network data (including HTTP)

19.
• Computers “think” very good in asynchronous
terms; humans do not…
• Without app structure, programming toward this
paradigm is difficult
• Ratpack ensures the most performant structures of
Netty are being utilized, while providing a sensible
app structure and programming model

20.
• Ratpack provides applications with a Netty-based, non-
blocking HTTP client
• Can be used to integrate with external RESTful services
• Utilizes the same event loop as the server, so resources
are appropriately utilized
• Provides a robust API for programmatically crafting
requests

21.
Above all else…
Ratpack is your
GATEWAY DRUG
to non-blocking

22.
• The JVM doesn’t have any concept of continuations, so
the only option we have is asynchronous APIs
• Async APIs allow callers to provide a completion
handler (or callback), which is to be invoked when some
processing has finished
• There is no temporal relationship between the caller
and the invocation of the callback

23.
handler { req, res ->!
... (1) do some work ...!
!
async {!
... (2) do some async work ...!
}!
async {!
... (3) do some more async ...!
}!
!
... (4) send response ...!
}!
(1) – Definitely finishes first
(2) – May finish before or after (3)
and (4)
(3) – May finish before or after (2) or
(4)
(4) – May finish before or after (2) or
(3)
Async APIs create non-determinism in control flow

24.
• The temporal disconnect creates non-determinism
in request processing
• This is a big problem for web applications, because
they demand a deterministic control flow
• Ratpack provides the concept of an Execution,
which creates determinism in asynchronous
processing

25.
handler { req, res ->!
... (1) do some work ...!
!
async {!
... (3) do some async work ...!
}!
async {!
... (4) do some more async ...!
}!
!
... (2) send response ...!
}!
(1) – Definitely finishes first
(3) – Definitely finishes third
(4) – Definitely finishes fourth
(2) – Definitely finishes second
Ratpack creates a deterministic control flow

26.
• Through Ratpack’s promise API, the Execution
is able to schedule async segments to be
invoked after the handler code has finished
• Promise API ensures that developers can work
with asynchronous processing in a sensible
way

27.
• In non-blocking, it is of paramount importance
to not block the thread
• Since a single thread is handling processing
for many clients, blocking one blocks all
• Need to adopt libraries that are non-blocking
or provide async APIs
• This is not always practical…

28.
• Not all interfaces are able to be non-blocking or
asynchronous
• Most non-blocking frameworks force you to be either
entirely async or wholesale define your handlers as
blocking
• This is limiting and makes it difficult to work with legacy
APIs or those not crafted for non-blocking work
• Ratpack gives you a mechanism to define blocking
execution segments in your handler code

29.
handler(r -> (ctx) -> {
ModelDAO dao = ctx.get(ModelDAO.class);
ctx.blocking(() ->
dao.load(ctx.getPathTokens().get("id")))
.then(model -> {
... do some work with the data ...
ctx.render(model);
});
})
Handler with blocking operation

30.
• Blocking operations are scheduled to an I/O
bound thread pool
• Once the blocking operation is completed,
the data is then returned to the request taking
thread, where processing can finish
• Blocking operations are invoked when they
are subscribed to in the request-taking thread

31.
...
ctx.blocking(() -> {
... do some blocking io ...
return result;
}).then(result -> {
... subscribe to the blocking promise ...
... process in the request-taking thread ...
})
...
Blocking with a subscription

32.
• Data is being delivered to web consumers in
an increasingly real time way
• Web applications must be able to support
streaming protocols like SSE and WebSockets
• Ratpack has built-in fixtures that make it easy
to develop real-time web applications

33.
• Because of its non-blocking nature, Ratpack can
support a high volume of concurrent real-time
streams
• Valuable in app-to-app communication too, where
a consumer wants to be reactively informed about
some data
• Ratpack’s HTTP client also supports reading
streams of data from external producers, making
stream processing a great integration

34.
• Ratpack applications are defined through a
handler chain
• Handler chain is a programmatic construct
for managing the flow of request data
• Handlers can be bound to request path
routes and HTTP verbs

35.
import static ratpack.groovy.Groovy.ratpack!
!
ratpack {!
handlers {!
get {!
response.send "I'm the default route!"!
}!
get("route1") {!
response.send "I'm in route1"!
}!
get("route2/:param") {!
response.send "I'm in route2 and received param: ${pathTokens.param}"!
}!
}!
}!
Handler chain in a Ratpack Script-backed app

36.
RatpackServer.start(b -> b
.config(ServerConfig.noBaseDir())
.handlers(chain -> chain
.get(ctx -> ctx.getResponse()
.send("I'm in the default route!"))
!
.get("route1", (ctx) -> ctx.getResponse()
.send("I'm in route1!"))
!
.get("route2/:param", (ctx) -> ctx.getResponse()
.send(String
.format(” received param: %s",
ctx.getPathTokens().get("param"))))
)
);"
Handler chain in using Java 8 APIs

37.
• Ratpack applications are defined through a
handler chain
• Handler chain is a programmatic construct
for managing the flow of request data
• Handlers can be bound to request path
routes and HTTP verbs

38.
handlers {!
get { ... }!
get("route") { ... }!
!
post { ... }!
post("route") { ... }!
!
put { ... }!
put("route") { ... }!
!
delete { ... }!
delete("route") { ... }!
!
patch { ... }!
patch("route") { ... }!
}!
Semantic handler API for binding to HTTP verbs and routes

39.
• Handlers can be nested within a route…
handlers {
prefix("api") { ModelDAO dao ->
get {
blocking { dao.getAll() }.
then { models -> render JsonOutput.toJson(models) }
}
post {
Model model = parse(fromJson(Model))
blocking { dao.save(model) }.
then { m -> render m }
}
put(":id") {
blocking { dao.load(pathTokens.id) }.
map { model -> model.merge(parse(fromJson(Model))) }.
blockingMap { model -> dao.save(model) }.
then { model -> render model }
}
}
}!

40.
• There’s a special handler type for serving
static assets from the app’s baseDir!
• Static assets must be defined as the last
handler in the chain
• Can be scoped to routes

41.
• Use the assets handler to serve static content
handlers {
prefix("api") {
get {
response.send "some API data"
}
}
assets("public", "index.html”)
}!

42.
• You can also use a handler with byMethod to perform common processing
within a route…
handlers {
handler("api") { ModelDAO dao ->
dao.beginTransaction()
byMethod {
get {}
post {}
put {}
delete {}
}
dao.endTransaction()
}!
}!

43.
• Can discriminate on content type, allowing you to build HyperMedia APIs…
handlers {
handler {
byContent {
json {
response.send(toJson([msg: "regular json"]))
}
xml {
response.send(...)
}
type("application/vnd.app.org+json;v=1") {
response.send(toJson([newmsg: "hypermedia json"]))
}
}
}
}!

44.
• Handlers define the edge of your application
• In Servlet API terms, handlers can be thought
of as a marriage between filters and servlets
• Allows request introspection and
programmatic injection of handler chain

45.
• This allows handlers to be constructed and dependency injected, etc…
class UserHandler implements Handler {
private final String message
UserHandler(String message) {
this.message = message
}
@Override
void handle(Context context) !
!throws Exception {
context.response.send(message)
}
}!
ratpack {
bindings {
bindInstance(new UserHandler("user handler"))
}
handlers {
handler { UserHandler userHandler ->
if (request!
.headers.contains("X-Routing-Header")) {
def routingHeader = request!
.headers.get("X-Routing-Header")
if (routingHeader == "user") {
insert(userHandler)
}
}
next()
}
get {
response.send "default system handler"
}
}
}!
New
Handler
is
programma1cally
inserted
into
the
processing
chain

46.
• Dependency injection is an abstraction in
Ratpack, through the concept of a Registry
• Components are bound to, and resolvable
from, a Registry instance
• Registries can be backed in a DI framework

47.
• Out of the box support for Guice and Spring
Boot
• Registries can be inherited, allowing
components to be resolved in a cascading
manner
• Every request context gets a registry that
components can be extracted from

48.
• In a Groovy script that uses closures as
handlers, the variable arguments to that
closure are “injected” from the registry
• In Java 8, they are able to be resolved from
the request context object

49.
• You don’t need to use a DI framework to get injection support, you can build
your own registry from objects you construct…
public static void main(String[] args) throws Exception {
Registry registry = Registries.registry()
.add(new ModelDAO()).add(new DB()).build();
RatpackServer.start(spec -> spec
.config(ServerConfig.noBaseDir())
.handlers(chain -> {
chain.register(registry);
chain.handler(":id", ctx -> {
ModelDAO dao = ctx.get(ModelDAO.class);
ctx.blocking(() ->
dao.load(ctx.getPathTokens().get("id")))
.then(ctx::render);
});
})
);
}!

50.
• Variables arguments to Groovy closure handlers are resolved from the
registry
def myRegistry = Registries.registry()
.add(new ModelDAO())
.build()
ratpack {
handlers {
register(myRegistry)
prefix("api") {
get(":id") { ModelDAO dao ->
render dao.load(pathTokens.id)
}
}
assets("public", "index.html”)
}
}!

51.
• In Groovy, you get a bindings block, which you can use to bind components
to the Registry. With Guice, annotations can be used to Inject
class UserHandler implements Handler {
private final ModelDAO dao
@javax.inject.Inject!
UserHandler(ModelDAO dao) {
this.message = message
}
@Override
void handle(Context ctx) !
!throws Exception {
ctx.blocking {!
dao.getAll()!
} then { ctx.render(it) }
}
}!
ratpack {
bindings {
binder { b ->
b.bind(ModelDAO).in(Scopes.SINGLETON)
b.bind(UserHandler).in(Scopes.SINGLETON)
}
}!
handlers {
handler { UserHandler userHandler ->
if (request!
.headers.contains("X-Routing-Header")) {
def routingHeader = request!
.headers.get("X-Routing-Header")
if (routingHeader == "user") {
insert(userHandler)
}
}
next()
}
get {
response.send "default system handler"
}
}
}!
Can
get
a
handle
on
a
Guice
binder
to
perform
annota1on-­‐based
Injec1ng

52.
• Likewise, a Guice Module can be “added” to the registry…
ratpack {
bindings {!
// Any Guice module can be added this way!
// this is how Ratpack modules are"
// introduced... "
add(new SqlModule())
}!
handlers {
...!
}
}!

53.
• Spring application context can be used to
back a registry using the
ratpack.spring.Spring class
h>p://www.ratpack.io/manual/0.9.13/api/ratpack/spring/Spring.html

54.
• Like handlers, registries can be
programmatically registered into the
handler chain based on request data
• Can allow your app to resolve components
specific to the context of a request

55.
• Likewise, a Guice Module can be “added” to the registry…
def baseRegistry = Registries.registry()
.add(new ModelDAO("jdbc:mysql://default"))
.build()
def cust1Registry = Registries.registry()
.add(new ModelDAO("jdbc:mysql://cust1"))
.build()
ratpack {
bindings {
bindInstance(new DefaultDevelopmentErrorHandler())
}
handlers {
handler {
next(get(PublicAddress).getAddress(it).host == "cust1" ? cust1Registry : baseRegistry)
}
prefix("api") {
get(":id") { ModelDAO dao ->
render blocking { dao.load(pathTokens.id) }
}
}
assets("public", "index.html”)
}
}!

56.
• Including framework modules in your
Gradle based project is really easy
• Can utilize helper methods from the
Ratpack Gradle plugin to include named
modules
• Allows framework versions to stay in sync

57.
• The Ratpack Gradle plugin provides the ratpack.dependency() helper
...!
!
dependencies {
compile ratpack.dependency("jackson”)
compile ratpack.dependency(”rxjava”)!
compile ratpack.dependency(”codahale-metrics”)!
testCompile ratpack.dependency(”remote-test”) !
}!
!
...!

58.
• Including framework modules in your
Gradle based project is really easy
• Can utilize helper methods from the
Ratpack Gradle plugin to include named
modules
• Allows framework versions to stay in sync

59.
• Static fixtures for mapping a multitude of external and environmental configuration
sources to POJOs
Configuration Module: ratpack-config
// build.gradle"
dependencies {!
...
compile ratpack.dependency(”config”)!
...
}!
import ratpack.config.*;!
!
ConfigurationData configData =
Configurations.config()
.yaml(Main.class.getResource("/app.yml"))
.json(Main.class.getResource("/app.json"))
.props("/etc/app/file.properties")
.sysProps()
.env()
.build();!
!
ServerConfig config = configData!
.get("/server", ServerConfig.class);
RatpackServer.start(spec -> spec
.config(config)
.handlers(...)
);!
// classpath:/app.yml"
server:!
port: 8080!
!
myAppStuff:!
anyConfigData: 1234!

60.
• Environment-derivable configuration
follows the principle of the Twelve Factor
App
Great Support for building MICROSERVICES!!

61.
• NetflixOSS Hystrix support, via the ratpack-
hystrix module
• Calls to remote services can be made fault
tolerant
• Ability to stream Hystrix metrics to the Hystrix
Dashboard
Great Support for building MICROSERVICES!!

62.
• The ratpack-hikari module uses HikariCP
to create a super fast pooled SQL DataSource
• Can be used in conjunction with Groovy SQL
to query databases
• Configurable using the fixtures from the
ratpack-config module
Great Support for DATABASES!!

63.
• The ratpack-jackson module provides
request data parsing and object rendering
from and to JSON
• Data can be worked with in free-form nodes,
or bound to command objects
• Arbitrary models can be rendered as JSON
using simply context.render(obj)!
Great Support for DATA BINDING!!

64.
• Ratpack’s Promise API is an implementation of
Reactive Streams Specification
• The ratpack-rxjava module provides a
bridge between a Ratpack Promise and an
RxJava Observable
• The ratpack-reactor module allows data
to be processed using Project Reactor
Great Support for REACTIVE PROGRAMMING!!

65.
• View templates can be rendered through a variety
of means
• Support for server-side templating with
Handlebars, Thymeleaf, Groovy Templates, and
Groovy Markup
• Ongoing work to integrate @davydotcom’s asset-
pipeline, which will give robust support for all types
of static content
Great Support for FULL-STACK FEATURES!!

66.
• Ratpack has been built from the ground-up with
testing considered at every turn
• Even more-so – considering testing from the
perspective of the developer
• The concept of the Registry gives the framework
control over components
• Makes it easy to provide fixtures for mocking and
stubbing data

67.
• The EmbeddedApp class from the ratpack-
test module supports functional and
integration testing
• Can be used to test an application module
or a subset of handlers and functionality
• Can be used outside of Ratpack too!

68.
• Spock is the choice framework, though
there’s no strict integration there
• Functional tests are easy to bootstrap and
the TestHttpClient helper makes it easy to
programmatically craft test calls

69.
• Great resource for seeing Ratpack’s testing
in action is the example-books project
• Rus Hart keeps this up to date with changes
to the framework.
• https://github.com/ratpack/example-books

70.
Twitter people to follow:!
!
• @ldaley!
• @rus_hart!
• @varzof!
• @Lspacewalker!
• @marcinerdmann!
• @ratpackweb!
• @davydotcom!
• @johnrengelman!
• @rfletcherEW!
• @beckje01!