Spring Boot - making configuration final

Question

My Spring Boot (1.3.5) application uses externalized configuration using an application.properties file. Alongside, I currently have a configuration class as such:

@Configuration
MyConfig {
   @Value("${prop}")
   private String prop;

   // getters
}

I'm wondering if there is a way to make prop final. Ideally I'd like to access my configuration properties publicly; for example myConfig.prop. I'd like to make all properties public and final; however I believe configuration classes are first instantiated via an empty constructor before properties are loaded. Is there an alternative approach?

It's not a runtime concern; rather it's to avoid inadvertent changes by other devs to the config. — user1491636, Jul 13 '16 at 15:37

Sleiman Jneidi · Answer 1 · 2016-07-05T20:32:40.667

1

You can inject your config values in the constructor and assign to a final field.

@Configuration
class MyConfig {
  private String final prop;
  public MyConfig(@Value("${prop}") String prop){
    this.prop = prop;
  }

 }

edited Jul 05 '16 at 20:32

answered Jul 05 '16 at 20:27

Sleiman Jneidi

22,907
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Yes that works. What if I have lots of configuration? I guess that is incentive to split it up into smaller config classes? – user1491636 Jul 05 '16 at 20:33
@user1491636 yes, you can do that, DBConfig and SMTPConfig can go into different config classes – Sleiman Jneidi Jul 05 '16 at 20:35
So after making this change, I get a startup exception: `No default constructor found;` – user1491636 Jul 06 '16 at 20:28
1

It's `private final String prop;`, not `private String final prop;`. – The SE I loved is dead Aug 31 '16 at 21:09

score 0 · Answer 2 · answered Nov 30 '20 at 11:11

0

For all the people landing here and asking themself the same question, please have a look at https://stackoverflow.com/a/57191291/11770752

In addition you can use this with lombok if desired, which reduces the class' boilerplate code.

answered Nov 30 '20 at 11:11

anjey

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The solution won't work for Spring Boot version 1.3.6 (specified in the question). – Petr Aleksandrov Nov 30 '20 at 11:52
you are right, just in case anybody for new versions (assuming which is the most part of the user) was curious i wanted them to provide further information. if this is somewhat bad, i'll excuse myself. – anjey Nov 30 '20 at 11:58

Spring Boot - making configuration final

2 Answers2