The @Value annotation can be used to inject values from external sources into fields, constructor parameters, or method parameters. To inject a system property, the annotation can use either the ${…} placeholder syntax or the #{…} SpEL expression syntax. The former is simpler and more concise, while the latter is more powerful and flexible. Both syntaxes can access the systemProperties map, which contains all the system properties as key-value pairs. Reference: : https://docs.spring.io/springframework/docs/current/reference/html/core.html#beans-value-annotations : https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#expressions : https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#expressionsbeandef-xml-based
