1. Overview
In this quick tutorial, we’ll explore the differences between Spring’s @RequestParam and @PathVariable annotations.
@RequestParam and @PathVariable can both be used to extract values from the request URI, but they are a bit different.
Learn how to validate request parameters and path variables with Spring MVC
Learn about the Spring @RequestBody and @ResponseBody annotations.
Have a look at the @ResponseStatus annotation and how to use it to set the response status code.
2. Query Parameter vs URI Path
While @RequestParams extract values from the query string, @PathVariables extract values from the URI path:
@GetMapping("/foos/{id}")
@ResponseBody
public String getFooById(@PathVariable String id) {
return "ID: " + id;
}
Then we can map based on the path:
http://localhost:8080/spring-mvc-basics/foos/abc
----
ID: abc
And for @RequestParam, it will be:
@GetMapping("/foos")
@ResponseBody
public String getFooByIdUsingQueryParam(@RequestParam String id) {
return "ID: " + id;
}
which would give us the same response, just a different URI:
http://localhost:8080/spring-mvc-basics/foos?id=abc
----
ID: abc
3. Encoded vs Exact Value
Because @PathVariable is extracting values from the URI path, it’s not encoded. On the other hand, @RequestParam is encoded.
Using the previous example, ab+c will return as-is:
http://localhost:8080/spring-mvc-basics/foos/ab+c
----
ID: ab+c
But for a @RequestParam request, the parameter is URL decoded:
http://localhost:8080/spring-mvc-basics/foos?id=ab+c
----
ID: ab c
4. Optional Values
Both @RequestParam and @PathVariable can be optional.
We can make @PathVariable optional by using the required attribute starting with Spring 4.3.3:
@GetMapping({"/myfoos/optional", "/myfoos/optional/{id}"})
@ResponseBody
public String getFooByOptionalId(@PathVariable(required = false) String id){
return "ID: " + id;
}
Then we can do either:
http://localhost:8080/spring-mvc-basics/myfoos/optional/abc
----
ID: abc
or:
http://localhost:8080/spring-mvc-basics/myfoos/optional
----
ID: null
For @RequestParam, we can also use the required attribute.
Note that we should be careful when making @PathVariable optional, to avoid conflicts in paths.
5. Conclusion
In this article, we learned the differences between @RequestParam and @PathVariable.
The full source code for the examples can be found over on GitHub.
