Spring Boot: a Quick Introduction
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This document provides an introduction and overview of Spring and Spring Boot frameworks. It discusses that Spring is an open-source framework that makes it easy to create Java-based enterprise applications. Spring Boot makes it easy to create production-grade Spring applications that can be "just run". The document outlines some of Spring's core features like the inversion of control container and aspect-oriented programming support. It also discusses Spring Boot's opinionated approach and how it abstracts common microservices tasks.
![Spring » beans and wiring I
(Spring) Bean: application object managed by the Spring IoC container
Configuration metadata tells the Spring container how instantiate, configure,
and assemble the objects in your application.
a) XML-based metadata
b) Java-based configuration
Java-based container configuration
Factory methods in Configuration classes can be annotated with Bean
Configuration public class AppConfig {
Bean public MyService myService() { return new MyServiceImpl(); }
public static void main(String[] args) {
ApplicationContext ctx =
new AnnotationConfigApplicationContext(AppConfig.class);
MyService myService = ctx.getBean(MyService.class);
myService.doStuff();
} }
PCD1718 Introduction Spring Boot 4/12](https://image.slidesharecdn.com/pcd1718-slides-spring-180616092247/85/Spring-Boot-a-Quick-Introduction-5-320.jpg)
![Hello Spring Boot
SpringBootApplication // tells Boot this is the bootstrap class
public class MyApp {
public static void main(String[] args){
SpringApplication.run(MyApp.class, args);
}
}
SpringBootApplication also implies
– EnableAutoConfiguration: tells Spring Boot to "guess" config by classpath
– ComponentScan: tells Spring to look for components
RestController RequestMapping(value="/app")
public class MyController {
RequestMapping(value="/hello/{name}", method = RequestMethod.GET)
public String hello( PathVariable("name") String name){
return "Hello, " + name;
}
}
Endpoint: http://localhost:8080/app/hello/Boot
Actuator also exposes http://localhost:8080/actuator/health
PCD1718 Introduction Spring Boot 9/12](https://image.slidesharecdn.com/pcd1718-slides-spring-180616092247/85/Spring-Boot-a-Quick-Introduction-10-320.jpg)
Spring Boot: a Quick Introduction
- 1. Spring An introduction Roberto Casadei Concurrent and Distributed Programming course Department of Computer Science and Engineering (DISI) Alma Mater Studiorum – Università of Bologna June 16, 2018 PCD1718 Introduction Spring Boot 1/12
- 2. Outline 1 Introduction 2 Spring Microservices with Spring Boot PCD1718 Introduction Spring Boot 2/12
- 3. Spring » intro What Spring: OSS framework that makes it easy to create JVM-based enterprise apps At its heart is an IoC container (managing beans and their dependencies) Also, notably: AOP support Term “Spring” also refers to the family of projects built on top of Spring Framework Spring Boot: opinionated, CoC-approach for production-ready Spring apps Spring Cloud: provides tools/patterns for building/deploying µservices Spring AMQP: supports AMQP-based messaging solutions... many others... Some History 2003 – Spring sprout as a response to the complexity of the early J2EE specs. 2006 – Spring 2.0 provided XML namespaces and AspectJ support 2007 – Spring 2.5 embraced annotation-driven configuration Over time, the approach Java enterprise application development has evolved. Java EE application servers – for full-stack monolithic web-apps Spring Boot/Cloud apps – for devops/cloud-friendly apps, with embedded server Spring WebFlux, released with Spring 5 in 2017, supports reactive-stack web apps PCD1718 Introduction Spring Boot 3/12
- 4. Spring » intro What Spring: OSS framework that makes it easy to create JVM-based enterprise apps At its heart is an IoC container (managing beans and their dependencies) Also, notably: AOP support Term “Spring” also refers to the family of projects built on top of Spring Framework Spring Boot: opinionated, CoC-approach for production-ready Spring apps Spring Cloud: provides tools/patterns for building/deploying µservices Spring AMQP: supports AMQP-based messaging solutions... many others... Some History 2003 – Spring sprout as a response to the complexity of the early J2EE specs. 2006 – Spring 2.0 provided XML namespaces and AspectJ support 2007 – Spring 2.5 embraced annotation-driven configuration Over time, the approach Java enterprise application development has evolved. Java EE application servers – for full-stack monolithic web-apps Spring Boot/Cloud apps – for devops/cloud-friendly apps, with embedded server Spring WebFlux, released with Spring 5 in 2017, supports reactive-stack web apps PCD1718 Introduction Spring Boot 3/12
- 5. Spring » beans and wiring I (Spring) Bean: application object managed by the Spring IoC container Configuration metadata tells the Spring container how instantiate, configure, and assemble the objects in your application. a) XML-based metadata b) Java-based configuration Java-based container configuration Factory methods in Configuration classes can be annotated with Bean Configuration public class AppConfig { Bean public MyService myService() { return new MyServiceImpl(); } public static void main(String[] args) { ApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class); MyService myService = ctx.getBean(MyService.class); myService.doStuff(); } } PCD1718 Introduction Spring Boot 4/12
- 6. Spring » beans and wiring II Spring-managed components Stereotypes: Component, Service, Controller, Repository Spring can automatically detect stereotyped classes and register corresponding BeanDefinitions with the ApplicationContext, via ComponentScan Configuration ComponentScan(basePackages="it.unibo.beans") public class AppConfig { } package it.unibo.beans; Service public class MyService { Autowired private ServiceA sa; // field injection public MyService(ServiceB sb){ ... } // constructor injection Autowired public void setServiceC(ServiceC sc){ .. } // setter injection } PCD1718 Introduction Spring Boot 5/12
- 7. Outline 1 Introduction 2 Spring Microservices with Spring Boot PCD1718 Introduction Spring Boot 6/12
- 8. Spring Boot Spring Boot makes it easy to create stand-alone, production-grade Spring-based Applications that you can just run It takes an opinionated view of the Spring platform and 3rd-party libraries Reasonable convention-over-configuration for getting started quickly It provides a light version of Spring targeted at Java-based RESTful µservices, without the need for an external application container It abstracts away the common REST microservice tasks (routing to business logic, parsing HTTP params from the URL, mapping JSON to/from POJOs), and lets the developer focus on the service business logic. Supported embedded containers: Tomcat 8.5, Jetty 9.4, Undertow 1.4 PCD1718 Introduction Spring Boot 7/12
- 9. Build configuration Build plugins spring-boot-maven-plugin for Maven spring-boot-gradle-plugin1 for Gradle Dependencies (cf., group ID org.springframework.boot) Starters are a set of convenient dependency descriptors to get a project up and running quickly. spring-boot-starter-web: starter for web, RESTful / MVC apps (Tomcat as default container) spring-boot-starter-actuator: gives production-ready features for app monitoring/management Run Maven tasks: spring-boot:run, package Gradle tasks: bootRun, bootJar 1https: //docs.spring.io/spring-boot/docs/current/gradle-plugin/reference/html/ PCD1718 Introduction Spring Boot 8/12
- 10. Hello Spring Boot SpringBootApplication // tells Boot this is the bootstrap class public class MyApp { public static void main(String[] args){ SpringApplication.run(MyApp.class, args); } } SpringBootApplication also implies – EnableAutoConfiguration: tells Spring Boot to "guess" config by classpath – ComponentScan: tells Spring to look for components RestController RequestMapping(value="/app") public class MyController { RequestMapping(value="/hello/{name}", method = RequestMethod.GET) public String hello( PathVariable("name") String name){ return "Hello, " + name; } } Endpoint: http://localhost:8080/app/hello/Boot Actuator also exposes http://localhost:8080/actuator/health PCD1718 Introduction Spring Boot 9/12
- 11. A path for learning Spring Boot I Spring Guides: https://spring.io/guides Do-It-Yourself Building an Application with Spring Boot https://spring.io/guides/gs/spring-boot/ Use RestController and RequestMapping to add endpoints. Create a SpringBootApplication class with main method. Consuming a RESTful Web Service https://spring.io/guides/gs/consuming-rest/ You use RestTemplate to make calls to RESTful services You can use RestTemplateBuilder to build RestTemplate Beans as needed. Building a Reactive RESTful Web Service (with Spring WebFlux) https://spring.io/guides/gs/reactive-rest-service/ (Optional) Creating Asynchronous Methods https://spring.io/guides/gs/async-method/ Declare Async methods (so they’ll run on a separate thread) that return CompletableFuture<T>. Annotate your app with EnableAsync and define an Executor Bean PCD1718 Introduction Spring Boot 10/12
- 12. A path for learning Spring Boot II (Optional) Messaging with RabbitMQ https://spring.io/guides/gs/messaging-rabbitmq/ (Optional) Messaging with Redis https://spring.io/guides/gs/messaging-redis/ Start redis: redis-server (default on port 6379) You need to configure (i) a connection factory to connect to the Redis server; (ii) a message listener container for registering receivers; and (iii) a Redis template to send messages. If the listener is a POJO, it needs to be wrapped in a MessageListenerAdapter. (Optional) Accessing Data Reactively with Redis https://spring.io/guides/gs/spring-data-reactive-redis/ Create a configuration class with Spring Beans supporting reactive Redis operations—cf., ReactiveRedisOperations<K,V> Inject ReactiveRedisOperations<K,V> to interface with Redis (Optional) Scheduling Tasks https://spring.io/guides/gs/scheduling-tasks/ EnableScheduling + Scheduled on a Component’s method. PCD1718 Introduction Spring Boot 11/12
- 13. References References I PCD1718 Appendix 12/12