Spring Boot

Notes about the SpringBoot framework in specific. Some of these topics might be useful in other frameworks as well which use the MVC principals.

dependencies

There are currently two methods of organizing dependencies for a SpringBoot project:

  1. Maven
  2. Gradel

I have chosen to go with Maven for now since it seems more popular, but I will say that Gradel looks vastly streamlined and simplified which is great. Even though its simplified, the pain points of Maven have been overcome with a decent IDE that will just add the entries for you. So, I think in this area, go with what your team decides to support.

Maven

The key file that maven uses is the pom.xml file at the root level of your project. Here is a structure of the addons or libraries your app will use to reference and which version of Java to be used for the project.

Some commands to up date your list of installed/downloaded libraries are as follows:

# install the dependencies
mvn dependency:tree
# build the jar
mvn build
# to start the app
mvn spring-boot:run

Mavens lifecycle has the following steps:

@startuml
skinparam shadowing false
skinparam monochrome true
[*] --> validate
validate -right-> compile
compile -right-> test
test --> package
package -left-> verify
verify -left-> install
install --> deploy
deploy -right-> [*]
@enduml

directory structure

  • src/main/java/com.pluralsight.conferencedemo/models
  • src/main/java/com.pluralsight.conferencedemo/controllers
  • src/main/java/com.pluralsight.conferencedemo/repositories
  • src/main/java/com.pluralsight.conferencedemo/services

Controllers

Purpose

respond to requests for their given path

Annotations

StatusCodes

The following example allows for you to return a status code of 201 for created instead of the standard status code of 200.

@PostMapping
@ResponseStatus(HttpStatus.CREATED)
public Session create(@RequestBody final Session sessions) {
    return sessionRepository.saveAndFlush(session);
}

Customization

To set custom environment variables for a SpringBoot application, there is a order of precedence that should be considered:

  1. Command line args
  2. SPRING_APPLICATION_JSON args
  3. Servlet parameters
  4. JNDI
  5. Java System Properties
  6. OS environment variables
  7. Profile properties
  8. Application properties
  9. @PropertySource annotations
  10. Default Properties

One pattern to choose is to:

  • Pick one interal source to set defaults
  • Pick one external to set the overrides

This allows you to have a list of variables that you can control without having too many surprizes.

properties

Appendix-Application-Properties

Overriding properties is pretty simple:

add the following to the src/main/resources/application.properties file to set the default server port to a value of 5000:

server.port = 5000

To set logging levels for your application your best bet is to use the application.properties file. SpringBoot allows you to create multiple profiles for selecting which profile you would like to use. Below are some examples of how to set your logging levels:

logging.level.org=WARN

Now when you start your application, you should find the following similar output:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.4.RELEASE)

2020-11-08 11:02:49.017  INFO 66643 --- [           main] c.p.c.ConferenceDemoApplication          : Starting ConferenceDemoApplication on macbook-pro.lan with PID 66643 (/Users/addlema/src/git.autodesk.com/conference-demo/target/classes started by addlema in /Users/addlema/src/git.autodesk.com/conference-demo)
2020-11-08 11:02:49.019  INFO 66643 --- [           main] c.p.c.ConferenceDemoApplication          : The following profiles are active: prd
2020-11-08 11:02:50.637  WARN 66643 --- [           main] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
2020-11-08 11:02:50.846  INFO 66643 --- [         task-1] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2020-11-08 11:02:50.995  INFO 66643 --- [         task-1] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
2020-11-08 11:02:51.974  INFO 66643 --- [           main] c.p.c.ConferenceDemoApplication          : Started ConferenceDemoApplication in 3.27 seconds (JVM running for 3.535)

Take note that even though we selected WARN level, we are still seeing INFO for the com namespace. Our settings are applied to the org namespace and will not be applied to the com space.

VSCode

ENVs

To set these environment variables to be used with VSCode, you need to create the following file of .vscode/launch.json and use something similar to below:

{
    "configurations": [
        {
            "type": "java",
            "name": "Spring Boot-ConferenceDemoApplication<conference-demo>",
            "request": "launch",
            "cwd": "${workspaceFolder}",
            "console": "internalConsole",
            "mainClass": "com.pluralsight.conferencedemo.ConferenceDemoApplication",
            "projectName": "conference-demo",
            "args": "",
            "env": {
                "DB_URL": "jdbc:postgresql://localhost:5432/conference_app"
            }
        }
    ]
}

Profiles

To set different application.properties files for various environments the following pattern is to create a file in the src/main/resources with the naming convention of appliation-NAME.properties where NAME would be the name of your enviornment. For example to set the properties for a Production environment you would create a file name of application-prd.properties or application-prod.properties. What ever you choose for the name would also be used in the .vscode/launch.json file as follows.

(this example is using prd as the name for the --spring.profiles.active argument is set to the value of prd)

{
    "configurations": [
        {
            "type": "java",
            "name": "Spring Boot-ConferenceDemoApplication<conference-demo>",
            "request": "launch",
            "cwd": "${workspaceFolder}",
            "console": "internalConsole",
            "mainClass": "com.pluralsight.conferencedemo.ConferenceDemoApplication",
            "projectName": "conference-demo",
            "args": "--spring.profiles.active=prd",
            "env": {
                "DB_URL": "jdbc:postgresql://localhost:5432/conference_app",
                "DB_USER": "postgres",
                "DB_PASS": "welcome"
            }
        }
    ]
}

If its yaml you prefer, SpringBoot will also pick up on the file of application.yml as well:

server:
    port: 5000

Best to keep to one type instead of mixing .properties with .yml and lower the confusion.

deployment

Default container for SpringBoot is Tomcat, but there are others like:

  1. Jetty
  2. Undertow
Next

Last updated on Oct 27, 2021