lab_01.adoc

Lab 1 - Getting Started with Spring Boot

Bootstrap the Project

1. In your browser, visit http://start.spring.io.

2. Fill out the Project metadata fields as follows:

   Group

   io.pivotal.spring

   Artifact

   hello-spring-boot

3. In the Dependencies section, search for web, and choose Web from the autocomplete menu.

4. Click the Generate Project button. Your browser will download a zip file. Unpack that zip file at $COURSE_HOME/labs/initial.

5. Import the project’s pom.xml into your editor/IDE of choice.

6. Add a @RestController annotation to the class io.pivotal.spring.HelloSpringBootApplication.

7. Add the following request handler to the class io.pivotal.spring.HelloSpringBootApplication:

   @RequestMapping("/")
   public String hello() {
       return "Hello World!";
   }

Build and Run with Embedded Apache Tomcat

Spring Boot will embed Apache Tomcat by default.

1. Build the application:

   $ ./mvnw package

2. Run the application:

   $ java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

   You should see the application start up an embedded Apache Tomcat server on port 8080:

   2015-12-06 17:17:30.507  INFO 60277 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
   2015-12-06 17:17:30.511  INFO 60277 --- [           main] io.pivotal.spring.HelloSpringBootApplication    : Started HelloSpringBootApplication in 3.201 seconds (JVM running for 3.846)

3. Visit the application in the browser (http://localhost:8080), and you should see the following:

   Hello World!

Build and Run with Embedded Eclipse Jetty

Spring Boot also supports embedding a Jetty server.

1. Open pom.xml and replace the following:

   <dependency>
   	<groupId>org.springframework.boot</groupId>
   	<artifactId>spring-boot-starter-web</artifactId>
   </dependency>

   with:

   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
       <exclusions>
           <exclusion>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-tomcat</artifactId>
           </exclusion>
       </exclusions>
   </dependency>
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-jetty</artifactId>
   </dependency>

2. Build the application:

   $ ./mvnw package

3. Run the application:

   $ java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

   You should see the application start up an embedded Jetty server on port 8080:

   2015-12-06 17:19:11.649  INFO 60588 --- [           main] .s.b.c.e.j.JettyEmbeddedServletContainer : Jetty started on port(s) 8080 (http/1.1)
   2015-12-06 17:19:11.654  INFO 60588 --- [           main] io.pivotal.spring.HelloSpringBootApplication    : Started HelloSpringBootApplication in 3.781 seconds (JVM running for 4.217)

4. Visit the application in the browser (http://localhost:8080), and you should see the following:

   Hello World!

Refactor to Externalize the Config

1. Rename src/main/resources/application.properties to src/main/resources/application.yml. Into that file, paste the following:

   greeting: Hello

2. To the class io.pivotal.spring.HelloSpringBootApplication, add a greeting field and inject its value:

   @Value("${greeting}")
   String greeting;

3. Also io.pivotal.spring.HelloSpringBootApplication, change the return statement of hello() to the following:

   return String.format("%s World!", greeting);

4. Build the application:

   $ ./mvnw package

5. Run the application:

   $ java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

6. Visit the application in the browser (http://localhost:8080), and verify that the output is still the following:

   Hello World!

7. Stop the application.

Using Environment Variables for Config

1. Run the application again, this time setting the GREETING environment variable:

   $ GREETING=Ohai java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

2. Visit the application in the browser (http://localhost:8080), and verify that the output has changed to the following:

   Ohai World!

3. Stop the application.

Using Spring Profiles for Config

1. Add a spanish profile to application.yml. Your finished configuration should reflect the following:

   greeting: Hello
   
   ---
   
   spring:
     profiles: spanish
   
   greeting: Hola

2. Build the application:

   $ ./mvnw package

3. Run the application, this time setting the SPRING_PROFILES_ACTIVE environment variable:

   $ SPRING_PROFILES_ACTIVE=spanish java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

4. Visit the application in the browser (http://localhost:8080), and verify that the output has changed to the following:

   Hola World!

5. Stop the application.

Resolving Conflicts

1. Run the application, this time setting both the SPRING_PROFILES_ACTIVE and GREETING environment variables:

   $ SPRING_PROFILES_ACTIVE=spanish GREETING=Ohai java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

2. Visit the application in the browser (http://localhost:8080), and verify that the output has changed to the following:

   Ohai World!

3. Visit http://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html to learn more about this outcome and the entire priority scheme for conflict resolution.