Question 1

Explanation

The symbol "$" is commonly used in @Value expressions to refer to the value of a property or environment variable.

The symbol "#{...}" is also used in @Value expressions to evaluate SpEL (Spring Expression Language) expressions and dynamically compute the value.

Spring Academy-related video: https://spring.academy/courses/spring-framework-essentials/lessons/spring-essentials-more-java-config-spel

See also:

${expr} --> Immediate Evaluation

#{expr} --> Deferred Evaluation

https://stackoverflow.com/questions/5322632/spring-expression-language-spel-with-value-dollar-vs-hash-vs#answer-20133659

Javadoc:

The EL supports both immediate and deferred evaluation of expressions. Immediate evaluation means that the expression is evaluated and the result returned as soon as the page is first rendered. Deferred evaluation means that the technology using the expression language can use its own machinery to evaluate the expression sometime later during the page’s lifecycle, whenever it is appropriate to do so.

Those expressions that are evaluated immediately use the ${} syntax. Expressions whose evaluation is deferred using the #{} syntax.

https://docs.oracle.com/javaee/6/tutorial/doc/bnahr.html