Path Variables

A path variable is a value written inside the URL itself, such as the 5 in /students/5. In the mapping you write a placeholder like /students/{id}, and @PathVariable captures the real value and passes it into the controller method. It is used to identify a specific resource (one student, one order, one course) in clean, readable REST URLs. Spring also converts the text to the parameter’s type, so "5" becomes a Long automatically.

Types

• Single variable: /students/{id} with @PathVariable Long id.
• Explicit name: @PathVariable("courseName") String course, when the variable and the parameter names differ.
• Multiple variables: /students/{id}/courses/{courseName}.
• Regex constraint: /students/{id:[0-9]+}, so only digits match.
• Optional variable: @PathVariable(required = false) or Optional<Long>, paired with two mappings.
• All variables as a Map: @PathVariable Map<String, String> vars.