Spring with Kotorin --8 Repository layer --Supplement: H2 Database

Overview / Description

Spring with Kotorin --8 Repository layer provides a repository layer to abstract the data persistence process and create an external persistence area. The operation to is made transparent.

In this case, the external persistence area used the H2 Database Engine, which runs in-memory and embedded in the application.

This H2 Database Engine has a built-in console application for checking database information. Let's check the status of the database using that.

Assumptions / Environment

Runtime version

Kotlin : 1.3.21
SpringBoot : 2.1.1.RELEASE

Spring Dependencies

Web
JDBC
JPA
H2
Actuator

Development environment

OS : Mac
IDE : IntelliJ IDEA
Build : Gradle

Procedure / Explanation

application.yml settings

Define the configuration information in SpringBoot's application.yml so that the H2 database can be used as follows.

Data source

Implement the data source definition for connecting to the database from Spring application as follows.

spring:
  datasource:
    driver-class-name: org.h2.Driver
    url: jdbc:h2:mem:app;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=TRUE
    username: guest
    password: guest

Component	Contents
driver-class-name	H2DB driver library `org.h2.Driver`
url	Database connection URL(* Format will be described later) `jdbc:h2:mem:app;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=TRUE`
username	Database connection username
password	Database connection password

H2 database connection URL format

The H2 database can take various operation modes such as using an application built-in type that operates in-memory, a server mode that operates as a remote server, and an operation that writes data to a file system. The connection URL format is suitable for each operation mode.

action mode	URL format	sample
Embedded mode: in-memory(private)	`jdbc:h2:mem:`	jdbc:h2:mem:
Embedded mode: in-memory(Named)	`jdbc:h2:mem:<DB name>`	jdbc:h2:mem:app
Built-in mode: Local file	`jdbc:h2:[file:][<File Path>]<DB name>`	jdbc:h2:file:/data/sample
In-memory DB drop prevention	DB_CLOSE_DELAY=-1	jdbc:h2:mem:app;DB_CLOSE_DELAY=-1
Server mode: TCP connection	jdbc:h2:tcp://[:]/[]	jdbc:h2:tcp://localhost:8084/data/sample
Server mode: TLS connection	jdbc:h2:ssl://[:]/[]	jdbc:h2:ssl://localhost/mem:test
DB connection disconnection at VM termination	DB_CLOSE_ON_EXIT=TRUE	jdbc:h2:mem:app;DB_CLOSE_ON_EXIT=TRUE

H2 database

Make the following settings to display the console screen of the H2 database.

spring:
  h2:
    console:
      enabled: true

Displaying the console screen of the H2 database

After launching the application, try accessing the H2 database console screen.

$ ./gradlew bootRun

> Task :bootRun

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.1.RELEASE)
:
:
:
2019-02-26 16:05:13.358  INFO 7073 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 15 endpoint(s) beneath base path '/admin'
2019-02-26 16:05:13.457  INFO 7073 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-02-26 16:05:13.460  INFO 7073 --- [           main] i.p.s.simple.SimpleApplicationKt         : Started SimpleApplicationKt in 5.577 seconds (JVM running for 5.998)
<==========---> 83% EXECUTING [2m 46s]
> :bootRun

--Access http: // localhost: [set port number] / h2-console and enter the connection user / password of the H2 database to connect.

Summary / Looking back

I tried to operate the H2 database that can be easily used in combination with SpringBoot. In application development situations that do not depend on the database function itself, there may be various situations where an easy-to-use H2 database can be used without installation work.

This source

shinyay/spring-just-rest-kotlin/tree/first-repository-layer