@ConditionalOnProperty does not have the same result in versions 1.5.* and 2.0.*

[hengyunabc]

@ConditionalOnProperty does not have the same result in versions 1.5.* and 2.0.*

Code

ConditionalOnProperty-demo.zip

application.properties:

test.fooKey=foo
test.bar-key=bar

	@Bean
	@ConditionalOnProperty(name = "test.fooKey")
	public static String fooKeyNoDash() {
		return "@ConditionalOnProperty(name = \"test.fooKey\")";
	}

	@Bean
	@ConditionalOnProperty(name = "test.foo-key")
	public static String fooKeyDash() {
		return "@ConditionalOnProperty(name = \"test.foo-key\")";
	}

	@Bean
	@ConditionalOnProperty(name = "test.barKey")
	public static String barKeyNoDash() {
		return "@ConditionalOnProperty(name = \"test.barKey\")";
	}

	@Bean
	@ConditionalOnProperty(name = "test.bar-key")
	public static String barKeyDash() {
		return "@ConditionalOnProperty(name = \"test.bar-key\")";
	}

Result

spring boot 1.5.13.RELEASE

application.properties: 

test.fooKey=foo
test.bar-key=bar

True  :@ConditionalOnProperty(name = "test.fooKey")
False :@ConditionalOnProperty(name = "test.foo-key")
True  :@ConditionalOnProperty(name = "test.barKey")
True  :@ConditionalOnProperty(name = "test.bar-key")

• @ConditionalOnProperty(name = "test.barKey") is True, because RelaxedPropertyResolver check all RelaxedNames of test.barKey .

spring boot 2.0.2.RELEASE

application.properties: 

test.fooKey=foo
test.bar-key=bar

True  :@ConditionalOnProperty(name = "test.fooKey")
True  :@ConditionalOnProperty(name = "test.foo-key")
False :@ConditionalOnProperty(name = "test.barKey")
True  :@ConditionalOnProperty(name = "test.bar-key")

• @ConditionalOnProperty(name = "test.foo-key") is True, because org.springframework.boot.context.properties.source.ConfigurationPropertyName

[snicoll]

The Javadoc of @ConditionalOnProperty in 2.0 mentions that you must use the canonical format. Both test.fooKey and test.barKey are invalid.

This is also mentioned in the migration guide and I just rephrased it slightly to make that a bit more explicit.

[hengyunabc]

@snicoll

I have a starter have to support both spring boot 1.5 and 2.0 .
The users have two kinds config in their code: test.fooKey=foo and test.foo-key=foo.

To support 1.5 users, I need to write @ConditionalOnProperty(name = "test.fooKey").
To support 2.0 users, I need to write @ConditionalOnProperty(name = "test.foo-key").

Finally, I found the solution:

public class FooAnyNestedCondition extends AnyNestedCondition {
	public FooAnyNestedCondition() {
		super(ConfigurationPhase.REGISTER_BEAN);
	}
	@ConditionalOnProperty(name = "test.fooKey")
	static class FooKey {
	}
	@ConditionalOnProperty(name = "test.foo-key")
	static class FooKeyStash {
	}
}

The code is confusing...

---

I suggest that marking @ConditionalOnProperty have the same result in versions 1.5.* and 2.0.*

[snicoll]

@hengyunabc thanks for the additional feedback. We don't really recommend having an auto-config that works with bot 1.5.x and 2.0.x as quite a few things have changed (relaxed binding is one of them). Having said that, you have a point about the migration use case. I've flagged this one for team attention to check with the rest of the team.

[snicoll]

@hengyunabc on a second look, that's not how you should define a property in 1.5.x. For relaxed binding to work properly there, you have to separate the prefix from the property, something like @ConditionalOnProperty(prefix = "test", "name="foo-key").

Also, the Javadoc of @ConditionalOnProperty requires you to use the dashed notation. If you do this the behaviour is consistent in 1.5.x and 2.0.x.

What is new in 2.0.x is that you don't have to separate the prefix from the property for relaxed binding to work properly.