Launching an application using Gradle

Typically, the very first step of creating any application is to have a basic startable skeleton. As the Spring Boot starter has created the application template for us already, all we have to do is extract the code, build, and execute it. Now let's go to the console and launch the application with Gradle.

How to do it...

Change the location of our directory to where the bookpub.zip archive was extracted from and execute the following command from the command line:

      $ ./gradlew clean bootRun
  

If you don't have gradlew in the directory, then download a version of Gradle from https://gradle.org/downloads or install it via Homebrew by executing brew install gradle. After Gradle is installed, run wrapper in the gradle folder to get the Gradle wrapper files generated. Another way is to invoke $gradleclean bootRun.

The output of the preceding command will be as follows:

    ...
      .   ____          _            __ _ _
     /\ / ___'_ __ _ _(_)_ __  __ _    
    ( ( )___ | '_ | '_| | '_ / _` |    
     \/  ___)| |_)| | | | | || (_| |  ) ) ) )
      '  |____| .__|_| |_|_| |___, | / / / /
     =========|_|==============|___/=/_/_/_/
     :: Spring Boot ::  (v2.0.0.BUILD-SNAPSHOT)
    
    2017-12-16 23:18:53.721 : Starting BookPubApplication on mbp with  
    PID 43850 
    2017-12-16 23:18:53.781 : Refreshing org.springframework.context.
    annotation.Annotatio
    2017-12-16 23:18:55.544 : Building JPA container 
    EntityManagerFactory for persistence 
    2017-12-16 23:18:55.565 : HHH000204: Processing 
    PersistenceUnitInfo [name: default  
    2017-12-16 23:18:55.624 : HHH000412: Hibernate Core  
    {5.2.12.Final}
    2017-12-16 23:18:55.625 : HHH000206: hibernate.properties not 
    found
    2017-12-16 23:18:55.627 : HHH000021: Bytecode provider name : 
    javassist
    2017-12-16 23:18:55.774 : HCANN000001: Hibernate Commons 
    Annotations {5.0.1.Final
    2017-12-16 23:18:55.850 : HHH000400: Using dialect: 
    org.hibernate.dialect.H2Dialect
    2017-12-16 23:18:55.902 : HHH000397: Using 
    ASTQueryTranslatorFactory
    2017-12-16 23:18:56.094 : HHH000227: Running hbm2ddl schema 
    export
    2017-12-16 23:18:56.096 : HHH000230: Schema export complete
    2017-12-16 23:18:56.337 : Registering beans for JMX exposure on 
    startup
    2017-12-16 23:18:56.345 : Started BookPubApplication in 3.024 
    seconds (JVM running...
    2017-12-16 23:18:56.346 : Closing 
    org.springframework.context.annotation.AnnotationC..
    2017-12-16 23:18:56.347 : Unregistering JMX-exposed beans on 
    shutdown
    2017-12-16 23:18:56.349 : Closing JPA EntityManagerFactory for 
    persistence unit 'def...
    2017-12-16 23:18:56.349 : HHH000227: Running hbm2ddl schema 
    export
    2017-12-16 23:18:56.350 : HHH000230: Schema export complete
    BUILD SUCCESSFUL
    Total time: 52.323 secs
  

How it works...

As we can see, the application started just fine, but as we didn't add any functionality or configure any services, it existed straight away. From the startup log, however, we do see that the autoconfiguration did take place. Let's take a look at the following lines:

    Building JPA container EntityManagerFactory for persistence unit 
    'default'
    HHH000412: Hibernate Core {5.2.12.Final}
    HHH000400: Using dialect: org.hibernate.dialect.H2Dialect
  

This information tells us that, because we added the jdbc and data-jpa starters, the JPA container was created and will use Hibernate 5.2.12.Final to manage the persistence using H2Dialect. This was possible because we had the right classes in the classpath.