Spring Boot basics, adopting and extending practices.

1. Spring Boot

2. Who Am I?
• You will find me here
https://github.com/tan9
http://stackoverflow.com/users/3440376/tan9
• My Java experience
• Java and Java EE development – 8+ years
• Spring Framework – 6+ years
• Spring Boot – 1.5 years
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3. Before We Get Started…
• Join the channel: http://bit.do/spring-boot
• Direct link: https://gitter.im/tan9/spring-boot-training
• Sign in using your GitHub account
• Or sign up right now!
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4. Spring Framework
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5. Spring Framework
• Inversion of Control (IoC) container
• Dependency Injection (DI)
• Bean lifecycle management
• Aspect-Oriented Programming (AOP)
• “Plumbing” of enterprise features
• MVC w/ RESTful, TX, JDBC, JPA, JMS…
• Neutral
• Does not impose any specific programming model.
• Supports various third-party libraries.
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6. Spring 2.5 JavaConfig
• Favor Java Annotation (introduced in Java SE 5)
• @Controller, @Service and @Repository
• @Autowired
• Thin XML configuration file
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<context:annotation-config/>
<context:component-scan
base-package="com.cht"/>

7. JavaConfig Keep Evolving
• @Bean & @Configuration since 3.0
• Get rid of XML configuration files.
• @ComponentScan, @Enable* and
@Profile since 3.1
• With WebApplicationInitializer powered by
Servlet 3, say goodbye to web.xml too.
• @Conditional since 4.0
• We’re able to filter beans programmatically.
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8. Maven Bill-Of-Materials (BOM)
• Keep library versions in ONE place.
• Import from POM’s <dependencyManagement>
section.
• Declare dependencies without <version>:
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<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
</dependency>

9. Things Getting Complicated
• Spring seldom deprecates anything
• And offers little opinion or guidance.
• Older approaches remain at the top in search results.
• Bootstrapping can be painful
• Due to the sheer size and growth rate of the portfolio.
• Spring is an incredibly powerful tool…
• Once you get it setup.
Should you use spring boot in your next project? - Steve Perkins
https://steveperkins.com/use-spring-boot-next-project/ 9

10. Spring Boot
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11. ThoughtWorks Technology Radar
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ThoughtWorks Techonlogy Rader April ‘16
https://www.thoughtworks.com/radar

12. Spring Boot
• Opinionated
• Convention over configuration.
• Production-ready non-functional features
• Embedded servers, security, metrics, health checks…
• Speed up
• Designed to get you up and running as quickly as
possible.
• Plain Java
• No code generation and no XML configuration.
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13. System Requirements
• Spring Boot 1.3 requires Java 7+ by default
• Java 8 is recommended if at all possible.
• Can use with Java 6 with some additional configuration.
• Servlet 3.0+ container
• Embedded Tomcat 7+, Jetty 8+, Undertow 1.1+.
• Oracle WebLogic Server 12c or later.
• IBM WebSphere Application Server 8.5 or later.
• JBoss EAP 6 or later.
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14. Boot With Apache Maven
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<project>
<modelVersion>4.0.0</modelVersion>
<groupId>com.cht</groupId>
<artifactId>inception</artifactId>
<version>0.0.1-SNAPSHOT</version>
<!-- Inherit defaults from Spring Boot -->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.5.RELEASE</version>
</parent>
<!-- Add typical dependencies for a web application -->
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<!-- Package as an executable jar -->
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

15. Starter POMs
• Make easy to add jars to your classpath.
• spring-boot-starter-parent
• Provides useful Maven defaults.
• Defines version tags for “blessed” dependencies.
• spring-boot-starter-*
• Provides dependencies you are likely to need for *.
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16. First Class
package com.cht.inception;
import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.web.bind.annotation.*;
@RestController
@EnableAutoConfiguration
public class Application {
@RequestMapping("/")
String home() {
return "Hello World!";
}
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
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17. mvn spring-boot:run
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. ____ _ __ _ _
/ / ___'_ __ _ _(_)_ __ __ _
( ( )___ | '_ | '_| | '_ / _` |
/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |___, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v1.3.5.RELEASE)
2016-07-03 23:38:04.683 INFO 93490 --- [ main] com.cht.inception.Application : Starting Application on
2016-07-03 23:38:04.685 INFO 93490 --- [ main] com.cht.inception.Application : No active profile set,
2016-07-03 23:38:04.718 INFO 93490 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springfra
2016-07-03 23:38:05.482 INFO 93490 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with
2016-07-03 23:38:05.491 INFO 93490 --- [ main] o.apache.catalina.core.StandardService : Starting service Tomcat
2016-07-03 23:38:05.491 INFO 93490 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine
2016-07-03 23:38:05.548 INFO 93490 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring emb
2016-07-03 23:38:05.548 INFO 93490 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationConte
2016-07-03 23:38:05.702 INFO 93490 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispa
2016-07-03 23:38:05.705 INFO 93490 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'charac
2016-07-03 23:38:05.705 INFO 93490 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hidden
2016-07-03 23:38:05.705 INFO 93490 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'httpPu
2016-07-03 23:38:05.705 INFO 93490 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'reques
2016-07-03 23:38:05.833 INFO 93490 --- [ main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerA
2016-07-03 23:38:05.876 INFO 93490 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/]}" onto jav
2016-07-03 23:38:05.879 INFO 93490 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" ont
2016-07-03 23:38:05.879 INFO 93490 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produc
2016-07-03 23:38:05.898 INFO 93490 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webja
2016-07-03 23:38:05.898 INFO 93490 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] o
2016-07-03 23:38:05.921 INFO 93490 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/fa
2016-07-03 23:38:05.986 INFO 93490 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for J
2016-07-03 23:38:06.032 INFO 93490 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(
2016-07-03 23:38:06.036 INFO 93490 --- [ main] com.cht.inception.Application : Started ⏎
Application in 1.529 seconds (JVM running for 4.983)

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19. Application Properties
• Place application.yaml in classpath
• For example:
• Configuring embedded server can be as easy as:
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server:
address: 127.0.0.1
port: 5566

20. YAML (YAML Ain’t Markup Language)
• Superset of JSON.
• UTF-8!
• Really good for hierarchical configuration data.
• But… can't be loaded via the @PropertySource.
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my:
servers:
- dev.bar.com
- foo.bar.com
my.servers[0]=dev.bar.com
my.servers[1]=foo.bar.com
YAML
Java Properties

21. Executable JAR
• $ mvn package
• Build and package the project.
• Spring Boot will repackage it into an executable one.
• $ java -jar target/
inception-0.0.1-SNAPSHOT.jar
• It’s just running.
• The jar is completely self-contained, you can deploy and
run it anywhere (with Java).
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22. Spring Boot: Dev
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23. Quick Start
• Spring Initializr Web Service
• http://start.spring.io
• SpringSourceTools Suite (eclipse-based)
• https://spring.io/tools/sts/all
• IntelliJ IDEA Ultimate (Costs $$$)
• https://www.jetbrains.com/idea/
• Or import Spring Initializr generated project from IntelliJ
IDEA Community Edition.
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24. Developer Tools
• Set dev properties, like disabling cache.
• Automatic restart when resources changed.
• LiveReload the browser.
• Remote update and debug.
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<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>

25. Externalized Configuration
1. Command line arguments.
2. Properties from SPRING_APPLICATION_JSON.
3. JNDI attributes from java:comp/env.
4. Java System properties (System.getProperties()).
5. OS environment variables.
6. RandomValuePropertySource for random.*.
7. Application property files.
8. @PropertySource on @Configuration.
9. SpringApplication.setDefaultProperties().
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26. Application Property Files Lookup
• Profile and File Type Priority
1. application-{profile|default}.properties / .yml / .yaml
2. application.properties/ .yml / .yaml
• Location Priority
1. A /config subdirectory of the current directory.
2. The current directory.
3. A classpath /config package.
4. The classpath root.
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27. Property Name Relaxed Binding
Property Note
person.firstName Standard camel case syntax.
person.first-name Dashed notation, recommended
for use in .properties and .yml files.
person.first_name Underscore notation, alternative
format for use in .properties and
.yml files.
PERSON_FIRST_NAME Upper case format. Recommended
when using a system environment
variables.
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28. @ConfigurationProperties
• It is Type-safe.
• More clear and expressive than
@Value("{connection.username}")
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@lombok.Data
@Component
@ConfigurationProperties(prefix = "connection")
public class ConnectionProperties {
private String username = "anonymous";
@NotNull
private InetAddress remoteAddress;
}

29. Incorporate Our @Configurations
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@Configuration
@EnableAutoConfiguration
@ComponentScan
public @interface SpringBootApplication {
...
}
@Order(Ordered.LOWEST_PRECEDENCE - 1)
public class
EnableAutoConfigurationImportSelector
implements DeferredImportSelector...

30. Configuration Override
Convention
• Always look up the properties list first
• http://docs.spring.io/spring-
boot/docs/current/reference/html/common-
application-properties.html
• Write @Configurations and @Beans if needed
• Then @ComponentScan them in.
• That’s what you are really good at.
• AutoConfigurations just serves as a fallback.
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31. Spring Boot: Run
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32. Spring Boot Actuator
“An actuator is a manufacturing term, referring to a
mechanical device for moving or controlling
something.
Actuators can generate a large amount of motion
from a small change.”
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<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

33. Production-Ready Endpoints
• Spring Configuration
• autoconfig, beans, configprops, env and mappings
• Logging & stats
• logfile, metrics, trace
• Informational
• dump, info, flyway, liquibase
• Operational
• shutdown
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34. Health Information
• Beans implements HealthIndicator
• You can @Autowired what you need for health
checking.
• Result will be cached for 1 seconds by default.
• Out-of-the-box indicators
• Application, DiskSpace, DataSource, Mail, Redis,
Elasticsearch, Jms, Cassandra, Mongo, Rabbit, Solr…
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35. Metrics
• Gauge
• records a single value.
• Counter
• records a delta (an increment or decrement).
• PublicMetrics
• Expose metrics that cannot be record via one of those
two mechanisms.
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36. Spring Boot: Ext
Custom AutoConfigurationsand ConfigurtaionProperties
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37. Auto Configuration
• META-INF/spring.factories
• Nothing special but @Configuration.
• Spring Boot will then evaluate all AutoConfiguration
available when bootstrapping.
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# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=
com.cht.inception.autoconfigure.DemoAutoConfiguration

38. @ConditionalOn*
• Eliminating all @Configuration will not work.
• Knowing and using built-ins where possible
• @ConditionalOnBean
• @ConditionalOnClass
• @ConditionalOnMissingBean
• @ConditionalOnMissingClass
• @ConditionalOnProperty
• … and more
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39. @Order matters
• Hints for Spring Boot
• @AutoConfigureAfter
• @AutoConfigureBefore
• You still have to know what underlying
• Not every operation is idempotent or cumulative.
• WebSecurityConfigurerAdapter for example.
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40. @ConfigurationProperties
• Naming things seriously
• There are only two hard things in Computer Science:
cache invalidation and naming things. -- Phil Karlton
• It will be an important part of your own framework!
• Generates properties metadata at compile time
• Located at META-INF/spring-configuration-
metedata.json.
• A Spring Boot-aware IDE will be great help for you.
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41. Deploying
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42. Package as WAR
• POM.xml
• <packaging>war</packaging>
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@SpringBootApplication
public class Application
extends SpringBootServletInitializer
implements WebApplicationInitializer {
...
}

43. JBoss EAP
• JBoss EAP v6.0 – 6.2
• Have to remove embedded server.
• JBoss EAP v6.x
• spring.jmx.enabled=false
• server.servlet-path=/*
• http://stackoverflow.com/a/1939642
• Multipart request charset encoding value is wrong.
• Have to downgrade JPA and Hibernate.
• JBoss EAP v7
• Haven’t tried yet.
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44. Oracle WebLogic Server
• WebLogic 11g and below
• Not supported.
• WebLogic 12c
• Filter registration logic is WRONG!
• https://github.com/spring-projects/spring-
boot/issues/2862#issuecomment-99461807
• Have to remove embedded server.
• Have to downgrade JPA and Hibernate.
• Have to specify <wls:prefer-application-
packages/> in weblogic.xml.
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45. IBM WebSphere AS
• WebSphere AS v8.5.5
• Have to remove embedded server.
• Have to downgrade JPA and Hibernate.
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46. What’s Next?
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47. Try JHipster
https://jhipster.github.io/
and to learn something from him.
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48. References
• Introduction to Spring Boot - Dave Syer, Phil Webb
• http://presos.dsyer.com/decks/spring-boot-intro.html
• Spring Boot Reference Guide
• http://docs.spring.io/spring-boot/docs/current/
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