[JAVA] How to change application.properties settings at boot time in Spring boot

The influence of the new corona is gradually beginning to appear in the workplace, and I am thrilled if I will stop working.

Meanwhile, I was addicted to it for the first time in a long time, so I decided to record it. Moreover, if you can understand it, it's a very simple story and it's quite dented. Perhaps it's too rudimentary for Java enthusiasts to publish to the Web. ..

Thing you want to do

• I want to read the configuration file and set the value when the application starts.

8h for such an easy thing.

Addictive points

• Rewriting classes / application.properties does not reflect the value.

Event reproduction

https://github.com/t-o-z/configuration-demo

Set up according to the Readme,

docker run config-demo

Then it is included in application.properties

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.4.RELEASE)

2020-02-27 09:51:15.557  INFO 7 --- [           main] c.z.c.ConfigurationDemoApplication       : Starting ConfigurationDemoApplication v0.0.1-SNAPSHOT on 6c889b4a8ada with PID 7 (/usr/src/myapp/configuration-demo-0.0.1-SNAPSHOT.jar started by root in /usr/src/myapp)
2020-02-27 09:51:15.566  INFO 7 --- [           main] c.z.c.ConfigurationDemoApplication       : No active profile set, falling back to default profiles: default
2020-02-27 09:51:16.918  INFO 7 --- [           main] c.z.c.ConfigurationDemoApplication       : Started ConfigurationDemoApplication in 2.482 seconds (JVM running for 3.809)
key1-value

Is displayed.

Apply application.properties under classes

sample.key1=key1-value1

Even if you rewrite it and execute it again

user:configuration-demo user$ docker run config-demo

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.4.RELEASE)

2020-02-27 09:58:45.004  INFO 6 --- [           main] c.z.c.ConfigurationDemoApplication       : Starting ConfigurationDemoApplication v0.0.1-SNAPSHOT on 9999dad12dac with PID 6 (/usr/src/myapp/configuration-demo-0.0.1-SNAPSHOT.jar started by root in /usr/src/myapp)
2020-02-27 09:58:45.014  INFO 6 --- [           main] c.z.c.ConfigurationDemoApplication       : No active profile set, falling back to default profiles: default
2020-02-27 09:58:46.425  INFO 6 --- [           main] c.z.c.ConfigurationDemoApplication       : Started ConfigurationDemoApplication in 2.564 seconds (JVM running for 3.881)
key1-value

It will not be reflected. ..

I tried various things.

• ** Try putting application.properties in classes / config **
  • https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#boot-features-external-config
• Try changing the method of reading settings
  • https://qiita.com/kazuki43zoo/items/0ce92fce6d6f3b7bf8eb
• Try to get the property directly from InputStream at startup and overwrite it
• (I'm sorry. I lost the URL I was referring to.)

Even if you check the countermeasures

• Prepare a configuration file for each environment
  • https://www.baeldung.com/spring-profiles
• Rewrite with command line arguments
  • https://stackoverflow.com/questions/37052857/spring-overriding-one-application-property-from-command-line
• Use Hot (Live) Reload
  • https://www.baeldung.com/spring-reloading-properties

There are various things like that, but is it possible to do it with just one file? I didn't have much information. The last Hot Reload is to set up a server just to do this.

Conclusion

** Copy to / config! ** **

I've already made it bold after trial and error,

classes/config

That's no good.

/config

Create a new one and place classes / application.properties in it.

sample.key1=modify

And start Docker (because it is COPY, rebuild is required).

Otsuka:configuration-demo otsukatakuya$ docker run config-demo

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.4.RELEASE)

2020-02-27 10:54:32.393  INFO 6 --- [           main] c.z.c.ConfigurationDemoApplication       : Starting ConfigurationDemoApplication v0.0.1-SNAPSHOT on c43d6b28259a with PID 6 (/usr/src/myapp/configuration-demo-0.0.1-SNAPSHOT.jar started by root in /usr/src/myapp)
2020-02-27 10:54:32.403  INFO 6 --- [           main] c.z.c.ConfigurationDemoApplication       : No active profile set, falling back to default profiles: default
2020-02-27 10:54:33.804  INFO 6 --- [           main] c.z.c.ConfigurationDemoApplication       : Started ConfigurationDemoApplication in 2.474 seconds (JVM running for 3.59)
modify

Where is it written?

https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#boot-features-external-config

It was mentioned in the official Spring boot reference.

SpringApplication loads properties from application.properties files in the following locations and adds them to the Spring Environment:

1. A /config subdirectory of the current directory

2. The current directory

3. A classpath /config package

4. The classpath root

The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).

I intended to try 1, but I couldn't try 3 first. .. Perhaps the classpath is in the jar and will conflict with it?

Some people have suggested a way to write exclusions in pom.xml and not include them in the build, but all you have to do is add them! I learned a lot because there were few articles that I wrote briefly.