Section 3.1: Syntax Reference

In Spring, you can use @Value("#{expression}") to inject values at runtime, where the expression is a Spring Expression Language (SpEL) expression. Here's a syntax reference for various use cases:

Literal Expressions

Supported types include strings, dates, numeric values (int, real, and hex), boolean, and null.

• String: #{'Hello World'}
• Numeric Values (Double): #{3.1415926}
• Boolean: #{true}
• Null: #{null}

Inline List

• List of Numbers: #{1,2,3,4}
• List of Lists: #{{'a','b'},{'x','y'}}

Inline Maps

• Map: #{name:'Nikola',dob:'10-July-1856'}
• Map of Maps: #{name:{first:'Nikola',last:'Tesla'},dob:{day:10,month:'July',year:1856}}

Invoking Methods

• String Length: #{'abc'.length()} (evaluates to 3)
• Method Invocation: #{f('hello')} (assumes f is a method in the class to which this expression belongs, taking a string parameter)

These examples demonstrate the flexibility of SpEL, allowing for the dynamic evaluation of expressions for value injection.