Spring boot is a suite, pre-configured, pre-sugared set of frameworks/technologies to reduce boilerplate configuration providing you the shortest way to have a Spring web application up and running with smallest line of code/configuration out-of-the-box.

1. Code Camp April-Spring Boot
April 2, 2016 Presented By - Nakul & Vishal

2. Audience
Beginner Level
Java Web Developers
Grails Developers

3. Objective
To get familiar with the Spring Boot framework and use it to build
microservices architecture.

4. Agenda
Introducing Spring Boot
Features
Artifacts
Profiling
Demo application using Spring
Boot and Groovy Templates

5. Introducing Spring Boot
- If Spring is the cake, Spring Boot is the
icing.

6. Spring boot is a suite, pre-configured, pre-sugared set of
frameworks/technologies to reduce boilerplate configuration providing you
the shortest way to have a Spring web application up and running with
smallest line of code/configuration out-of-the-box.
What is Spring Boot ?

7. The primary goals of Spring Boot are:
To provide a radically faster and widely accessible 'getting started'
experience for all Spring development
To be opinionated out of the box, but get out of the way quickly as
requirements start to diverge from the defaults
To provide a range of non-functional features that are common to large
classes of projects (e.g. embedded servers, security, metrics, health
checks, externalized configuration)
Spring Boot does not generate code and there is absolutely no requirement
Why Spring Boot ?

8. import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.stereotype.*;
import org.springframework.web.bind.annotation.*;
@Controller
@EnableAutoConfiguration
@Configuration
@ComponentScan
//All three annotations can be replaced by one @SpringBootApplication
public class SampleController {
@RequestMapping("/")
String home() {
return "Hello World!";
}
public static void main(String[] args) throws Exception {
SpringApplication.run(SampleController.class, args);
}
A simple Spring Boot Application

9. Demo
Let’s hit some keys !!
Hello World from Spring Boot

10. ❖@Controller - annotates a class as an MVC controller
❖@Configuration - tags the class as a source of bean definitions for the
application context.
❖@EnableAutoConfiguration - enables auto configuration for the
application
❖@ComponentScan - This tells Spring to look for classes with
@Component ,@Configuration , @Repository , @Service , and
@Controller and wire them into the app context as beans.
❖@SpringBootApplication - get the functionality of all above annotations
in a single annotation
Whats Happening?

11. How Spring boot works ?

12. Directory Structure of Spring Boot
There is no restrictions on directory
structure.
We can create one as we are used to in
grails or we can create one that is shown
in the picture.

13. Demo
Let’s hit some keys !!
Look at the directory structure

14. Spring Boot Essentials
Spring Boot brings a great deal of magic to Spring application development.
But there are four core tricks that it performs:
■ Automatic configuration — Spring Boot can automatically provide
configuration for application functionality common to many Spring applications.
■ Starter dependencies — You tell Spring Boot what kind of functionality you need,and it
will ensure that the libraries needed are added to the build.
■ The command-line interface — This optional feature of Spring Boot lets you write
complete applications with just application code, but no need for a traditional project
build.
■ The Actuator — Gives you insight into what’s going on inside of a running Spring Boot
application.

15. What Spring Boot isn’t ?
1. Spring Boot is not an application server. It has embedded server that helps
it run by executing a jar file of the project.
1. Spring Boot doesn’t implement any enterprise Java specifications such as
JPA or JMS. It auto configures these beans and provide them at runtime to
our disposal.
1. Spring Boot doesn’t employ any form of code generation to accomplish its
magic. Instead, it leverages conditional configuration features from Spring,
along with transitive dependency resolution offered by Maven and Gradle,
to automatically configure beans in the Spring application context.

16. Basic Artifacts
Dependency Resolution
Domains
Repositories
Controllers
Services
Views
Configuration
Deployment

17. 1. Done with the help of Gradle or Maven.
2. Dependencies are resolved by build.gradle in gradle build environment.
3. For maven they are resolved from pom.xml
4. Gradle supports groovy DSL like syntax and is much easier to maintain.
It frees us from the fuss of writing xml for dependency resolution.
Dependency Resolution

18. Resolving dependencies using Gradle
Let’s have a look at the build.gradle file in the root of our
application.

19. Demo
Let’s hit some keys !!
build.gradle

20. 1. Annotated by the annotation @Entity
2. javax.persistence.Entity/grails.persistence.Entity/org.hibernate.annotat
ions.Entity
3. Can use JPA 2.1, Hibernate, Spring Data, GORM etc .
4. Classes annotated by @Entity is a component which our main class
searches for by the help of @ComponentScan
Domains

21. Demo
Let’s hit some keys !!
Domains

22. 1. Provides abstraction.
2. Significantly reduces the amount of boilerplate code required to
implement DAO layer
3. Supports various persistence stores like MySql , MongoDB etc.
The central interface in Spring Data repository abstraction is Repository.It
takes the the domain class to manage as well as the id type of the domain
class as type arguments.
This interface acts primarily as a marker interface to capture the types to
work with and to help you to discover interfaces that extend this one.
Repositories

23. The CrudRepository provides sophisticated CRUD functionality for the entity class that is being managed.
public interface CrudRepository<T, ID extends Serializable>
extends Repository<T, ID> {
S save(S entity); //Saves the given entity
T findOne(ID primaryKey); //Returns the entity identified by the given id
Iterable<T> findAll(); //Returns all entities
Long count(); //Returns the number of entities
void delete(T entity); //Deletes the given entity
boolean exists(ID primaryKey); //Indicates whether an entity with the given id exists
// … more functionality omitted.
}

24. How a repository works ?
1. Declare an interface extending Repository or one of its subinterfaces and type it to the domain
class that it will handle.
public interface PersonRepository extends Repository<User, Long> { … }
1. Declare query methods on the interface.
List<Person> findByLastname(String lastname);
1. Get the repository instance injected and use it.
public class SomeClient {
@Autowired
private PersonRepository repository;
public void doSomething() {
List<Person> persons = repository.findByLastname("Nakul");
}
}

25. Demo
Let’s hit some keys !!
Repositories

26. 1. Any java class can be converted into a controller by annotating it with
@Controller or @RestController
2. @Controller - makes a java/groovy class as an MVC controller that
renders a view
3. @RestController - makes a java/groovy class as a rest controller.
Controllers

27. What about ‘actions’ ?
Any method defined inside a class annotated by @Controller or @RestController will behave like an
action only if it has been annotated by @RequestMapping
Ex - @RestController
@RequestMapping(value = '/student')
class RootController {
@Autowired
StudentRepository studentRepository
@RequestMapping(method=RequestMethod.GET ,value = '{id}',produces =
MediaType.APPLICATION_JSON_VALUE)
public Student getOne(@PathVariable String id) {
return studentRepository.findOne(Long.parseLong(id))
}
}

28. What about ‘actions’ ? Continued -
A simple MVC controller
Ex - @Controller
@RequestMapping(value = '/student')
class RootController { @Autowired
StudentRepository studentRepository
@RequestMapping(method=RequestMethod.GET ,value = '{id}')
public ModelAndView getOne(@PathVariable String id) {
return new ModelAndView(“views/index”,[:])
}
}

29. Demo
Let’s hit some keys !!
Controllers and Actions

30. 1. Any java/groovy class can be converted into a service by annotating it
with @Service
2. To make a service transactional mark it with @Transactional
3. @Transactional(propagation = REQUIRED) makes a transaction
complete in itself
4. @Transactional(propagation = MANDATORY) is used to protect the
other methods from being called erroneously out of a transaction
5. @Transactional(readOnly=true) makes a service read-only.
Services

31. Demo
Let’s hit some keys !!
Services

32. 1. Spring supports Groovy template engine natively to render views
modelled by the controller.
2. Thymeleaf is also a popular rendering engine being used with spring-
boot
3. GSP’s can also be used as a part of presentation layer.
4. We can also use Angular.js as a frontend framework for use with REST-
API’s for make a complete web-app.
Views

33. From where can we get these rendering engines ?
Can be maintained as gradle dependencies in build.gradle
Dependencies
Groovy Template Engine - compile ("org.codehaus.groovy:groovy-templates:2.4.0")
Thymeleaf Engine - compile("org.springframework.boot:spring-boot-starter-thymeleaf")
Groovy Server Pages - compile "org.grails:grails-web-gsp:2.5.0"
compile "org.grails:grails-web-gsp-taglib:2.5.0"
provided "org.grails:grails-web-jsp:2.5.0"

34. Groovy Template Engine
Features
1. hierarchical (builder) syntax to generate XML-like contents (in particular,
HTML5)
2. template includes
3. compilation of templates to bytecode for fast rendering
4. layout mechanism for sharing structural patterns

35. Groovy Template Engine
Dependency
dependencies {
compile "org.codehaus.groovy:groovy"
compile "org.codehaus.groovy:groovy-templates"
}

36. Groovy Template Engine
Example 1
link(rel: 'stylesheet', href: '/css/bootstrap.min.css')
will be rendered as:
<link rel='stylesheet' href='/css/bootstrap.min.css'/>

37. Groovy Template Engine
Example 2
a(class: 'brand',
href: 'http://beta.groovy-lang.org/docs/groovy-2.3.2/html/documentation/markup-template-
engine.html',
'Groovy - Template Engine docs')
will be rendered as:
<a class='brand' href='http://beta.groovy-lang.org/docs/groovy-2.3.2/html/documentation/markup-
template-engine.html'>Groovy - Template Engine docs</a>

38. Groovy Template Engine
Example 3
a(class: 'brand', href:‘http://beta.groovy-lang.org/docs/groovy-2.3.2/html/documentation/markup-
template-engine.html'){
yield 'Groovy - Template Engine docs'
}
will be rendered as:
<a class='brand' href='http://beta.groovy-lang.org/docs/groovy-2.3.2/html/documentation/markup-
template-engine.html'>Groovy - Template Engine docs</a>

39. Demo
Let’s hit some keys !!
Views

40. Groovy Template Engine - Layouts
Layouts-Example
yieldUnescaped '<!DOCTYPE html>'
html {
head {
title(pageTitle)
link(rel: 'stylesheet', href: '/css/bootstrap.min.css')
}
body {
a(class: 'brand',
href: 'http://beta.groovy-lang.org/docs/groovy-2.3.2/html/documentation/markup-template-
engine.html',
'Groovy - Template Engine docs')

41. Groovy Template Engine - Layouts
Layouts - Example
a(class: 'brand',
href: 'hhttp://projects.spring.io/spring-boot/') {
yield 'Spring Boot docs'
mainBody()
}
}
}

42. Groovy Template Engine - Layouts
Layouts
1. Common part of our template is kept into a main.tpl file that we will save
into src/main/resources/templates/layouts
2. title(pageTitle) where pageTitle is expected to be the page title that we want
to give
3. mainBody(), which will cause rendering of the main body for pages using
that layout.

43. Groovy Template Engine - Layouts
Layouts in action
layout 'layouts/main.tpl',
pageTitle: 'Spring Boot - Groovy templates example with layout',
mainBody: contents {
div("This is an application using Spring Boot and Groovy Template Engine")
}

44. Groovy Template Engine - Layouts
Layouts
we call the layout method and provide it with several arguments:
the name of the layout file to be used (layouts/main.tpl)
pageTitle, a simple string
mainBody, using the contents block

45. Groovy Template Engine - Layouts
Layouts
Use of the contents block will trigger the rendering of the contents of mainBody
inside the layout when the mainBody() instruction is found. So using this layout
file, we are definitely sharing a common, structural pattern, against multiple
templates.
layouts are themselves composable, so you can use layouts inside layouts…

46. Demo
Let’s hit some keys !!
Layouts

47. Profiles
Profiles
In the normal Spring way, you can use a spring.profiles.active Environment
property to specify which profiles are active.
specify on the command line using the switch
--spring.profiles.active=dev
--spring.profiles.active=test
--spring.profiles.active=production
For every environment we create a application-{environment}.properties files in
the resource directory.

48. application.properties
application.properties
If no environment is specified then spring boot picks the default
application.properties file from the ‘resources’ directory.
Stores all the configurations in a single file .
All the configurable properties can be referenced here

49. Demo
Let’s hit some keys !!
Profiles

50. References
References
Groovy Templates : https://spring.io/blog/2014/05/28/using-the-innovative-
groovy-template-engine-in-spring-boot
Spring Boot : Spring Boot in Action - Craig Walls, Manning Publication
Learning Spring Boot - Greg L. Turnquist, Packt
Publishing
More References - http://docs.spring.io/spring-
boot/docs/current/reference/htmlsingle/

51. Questions ?

52. For dummy project please visit https://github.com/pant-nakul/springboot-crud-
demo

53. Thank You for your patience !!!