Storing JVM system properties in the Spring Environment as Properties can degrade performance due to synchronization

systemProperties PropertySource in Environment implemented with Properties ,But Properties is synchronous, which will reduce performance !!!

[sbrannen]

The system properties are actually stored in a PropertiesPropertySource which by default delegates to System.getProperties() as the source. That happens to be a synchronized Hashtable which implements Map.

So I guess the question is why AbstractEnvironment.getSystemProperties() delegates to System.getProperties() by default, when it could always create a ReadOnlySystemAttributesMap.

Of course, as you mentioned @rstoyanchev, we’d need to know when the synchronization of the system properties is problematic.

[sbrannen]

Even our ReadOnlySystemAttributesMap arrangement delegates to System.getProperty though, hitting the synchronized Properties instance underneath.

Indeed. I was thinking ReadOnlySystemAttributesMap made an upfront copy. Mea culpa.

If system properties are never supposed to be checked at all for performance reasons, maybe we need a setting along the lines of the existing “spring.getenv.ignore”… either for system properties specifically, or for the combination of system properties and system environment checks (since I suppose typically neither of those is needed then).

I agree. Something like spring.env.system.properties.cache=true could signal that JVM system properties should be retrieved once and cached in a read-only map. And the same would hold for spring.env.environment.variables.cache=true (though naming is always a challenge).