1. 1. By : Jaspereet Juneja & Sourabh Aggarwal Date : 30 July 2015 SPRING BOOT
2. 2. What is Spring Boot? Spring Boot is a approach to develop Spring based application with very less or no configuration. It leverages existing Spring projects as well as Third party projects to develop production ready applications. It provides a set of Starter Poms, gradle etc.. build files which one can use to add required dependencies and also facilitate auto configuration. Depending on the libraries on its classpath, Spring Boot automatically configures required classes. For example to interact with DB, if there is Spring Data libraries on class path then it automatically sets up connection to DB along with the Data Source class.
3. 3. Spring Boot focus point?
4. 4. Why to use spring boot? Create stand-alone Spring applications Embed Tomcat, Jetty or Undertow directly (no need to deploy WAR files) Provide opinionated 'starter' POMs to simplify your Maven configuration Automatically configure Spring whenever possible Provide production-ready features such as metrics, health checks and externalized configuration Absolutely no code generation and no requirement for XML configuration.
5. 5. Spring Boot Modules? Boot Autoconfigure Starters CLI Actuator Tools Samples
6. 6. Spring Boot Modules? Spring Boot - main library supporting the other parts of Spring Boot Spring Boot Autoconfigure - single @EnableAutoConfiguration annotation creates a whole Spring context Spring Boot Starters - a set of convenient dependency descriptors that you can include in your application. Spring Boot CLI - compiles and runs Groovy source as a Spring application Spring Boot Actuator - common non-functional features that make an app instantly deployable and supportable in production Spring Boot Tools - for building and executing self-contained JAR and WAR archives Spring Boot Samples - a wide range of sample apps
7. 7. Spring Boot Actuator? Its a Spring Boot module that immediately gives your Spring-based web applications basic health check and monitoring interfaces. To use it just add Maven dependency spring-boot-starter-actuator. If you now recompile and restart your service, youll notice that a lot more endpoints are being mapped (this is printed to the log during startup). Some of these are: /health returns ok as text/plain content which is useful for simple service monitoring /env check environment configuration, property file and command line argument overrides, active profiles /metrics basic statistics on your service endpoints (e.g. hit count, error count) /dump thread dump /trace the latest HTTP request/response pairs You can access/modify (or change completely if you wish) the behavior for most of these. For example, if you want to add a custom metric, just inject a MetricRepository in your business beans, and start using it, itll get exposed via the Actuator /metrics interface.
8. 8. Spring Boot over Spring Opinionated Convention Over Configuration Automatic Configuration Starter + Example Builds Standalone Apps No XML! Embedded Containers Metrics (Actuator) Groovy
9. 9. Hello World(Java) import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.EnableAutoConfiguration; import org.springframework.web.bind.annotation.*; @RestController @EnableAutoConfiguration public class MyApplication { @RequestMapping("/hello") public String sayHello() { return "Hello World!"; } public static void main(String[] args) { SpringApplication.run(MyApplication.class, args); } }
10. 10. @EnableAutoConfiguration Attempts to auto-configure your application Backs off as you define your own beans @Configuration @EnableAutoConfiguration public class MyApplication { }
11. 11. Starter POMs org.springframework.bootspring-boot-starter-web Standard Maven POMs Define dependencies that we recommend Parent optional Available for web, batch, integration, data, amqp, aop, jdbc, ... e.g. data = hibernate + spring-data + JSR 303
12. 12. Packaging For Production Maven plugin (using spring-boot-starter-parent): org.springframework.bootspring-boot-maven-plugin $ mvn package
13. 13. Annotations We are relying on Springs annotation and package-scan based approach to configure our controller @EnableAutoConfiguration is specific to Spring Boot and declaring it will result in a lot of pre-defined configuration pulled to our Spring Application Context (like the embedded Tomcat container) SpringApplication is another Boot-specific component, its the default entry point for most of the Spring Boot applications and will take care of the Spring Application Context for us. And that is all you actually need. At this point you should be able to start this application from your favourite IDE, launching class HelloConfiguration. Then visit http://localhost:8080/hello which should result in Hello World! being displayed in your browser.
14. 14. Problems? Although most features that Spring Boot gives you are extremely useful and work very well immediately, we encountered a few cases where a bit of caution is recommended: Spring Boot will import and use Logback and SLF4J as default loggers. If you want to use something else (e.g. Log4J) or one of your dependencies transitively imports it, you need to be careful and use the appropriate logger bridges. Some combinations may result in your applications not starting at all. Maven exclusions for transitive dependencies will come handy. The Spring Boot Maven Builder packages executable jar files in a specific way, effectively adding multiple levels of nested jar files. This is a problem if your libraries want to extract contents from the nested jar files as Java wont be able to resolve that resource path. Consider using a different packaging mechanism like Shade or AppAssembler in such cases. Spring Boot Maven Parent comes with a basic configuration for Shade, but the preferred choice should be the Boot-builder. We advise some level of caution if you want to use embedded application servers and JSPs with Spring Boot, there may be some limitations.
15. 15. Overriding default configuration Using property files? Overriding with command line arguments? Support for Spring profiles? Overriding default beans?
16. 16. Using property files? By default Spring Boot will look for a property file in the package root directory called application.properties, this is a good place to customize your application. By Maven conventions, place this file into the src/main/resources directory so your build artefacts will be generated correctly. For example lets set the contents to: server.port=11000 This will cause the embedded Tomcat to listen on port 11000 instead of 8080. If you now restart your service, you should use http://localhost:11000/hello to get access. Finding out what is given by default and what you can override is probably the biggest problem with Spring Boot at the moment. There is no comprehensive documentation about all the options, but the code in org.springframework.boot.autoconfigure.* packages is a good starting point. (e.g. server.port is bound to a field in org.springframework.boot.autoconfigure.web.ServerProperties as of Boot 1.0.0.RC3).
17. 17. Overriding with command line arguments? If you need more execution-specific parameter use, you can do it. The usual convention of the property overriding chain: defaults < property files < Java VM arguments is still valid, but Spring Boot will also give you Springs command-line argument property source: with double dashes () arguments when executing your application, you can specify property overrides: $ java -jar spring-boot-example-0.0.1-SNAPSHOT.jar --server.port=12000 As you probably have already figured out, this will result in your webserver listening on port 12000 and your application available on http://localhost:12000/hello
18. 18. Support for Spring profiles? Spring Boot actively supports the usage of Spring Profiles. First, to activate a profile, you can use the double-dash command line argument syntax: spring.profiles.active and list those that you want activated. Additionally, you can name your property files in the following way: application-{profile}.properties And only those that match one of the active profiles will get loaded. Regarding your Spring beans, you can rely on the @Profile annotation to work as expected.
19. 19. Overriding default beans When pulling a spring-boot-starter project as a dependency, Boot will declare the most commonly needed beans. For example, in case of a web project, you will get a DispatcherServlet without having to do anything (usually, you can configure these default beans with externalized properties). In the majority of the cases this will be sufficient. However, if you want to have more control over these beans, just declare them as you normally would and your beans will override the ones given by Boot (in fact, Boot wont even instantiate any of its default beans if you have an overriding bean).