Differences Betwixt @Requestparam Too @Pathvariable Annotations Inward Restrain Mvc?

The Spring MVC framework, i of the most pop frameworks for developing a spider web application inward Java the world besides provides several useful annotations to extract information from the incoming asking too mapping the asking to controller e.g. @RequestMapping, @RequestParam, too @PathVariable. Even though both @RequestParam and @ParthVariable is used to extract values from the HTTP request, at that topographic point is a subtle departure betwixt them, which makes them a useful inquiry from an interview too spring certification betoken of view. We'll test the subtle departure between @RequestParam too @PathVaraible inward this article. As the get upwardly suggests @RequestParam is used to acquire the asking parameters from URL, besides known every bit query parameters, piece @PathVariable extracts values from URI.

For example, if the incoming HTTP asking to holler back a majority on theme "Java" is http://localhost:8080/shop/order/1001/receipts?date=12-05-2017, too then y'all tin role the @RequestParam annotation to holler back the query parameter date too y'all tin role @PathVariable to extract the orderId i.e. "1001" every bit shown below:

@RequestMapping(value="/order/{orderId}/receipts", method = RequestMethod.GET)
public List listUsersInvoices(                               @PathVariable("orderId") int order,
 @RequestParam(value = "date", required = false) Date dateOrNull) {
...
}

The required=false denotes that query parameter tin last optional but the URL must conduct maintain the same URI.

How to extract Query Parameters inward Spring MVC using @RequestParam

Spring MVC is a rich framework to educate both spider web applications too RESTful spider web services inward Java. It provides several ways to holler back information from the incoming HTTP requests e.g.

• Request Parameters
• Path Variables
• Form inputs

Now that y'all know the departure betwixt @RequestParam too @PathVariable inward Spring MVC, let's run across how to write Spring controllers that tin grip asking parameters too path variables.

Using @RequestParam to acquire Query parameters

In a Spring MVC application, y'all tin role the @RequestParam annotation to convey query parameters inward Controller's handler methods.

For examples, suppose y'all conduct maintain a spider web application which returns details of orders too trades too y'all conduct maintain next URLs:

http://localhost:8080/eportal/orders?id=1001

To convey the query parameters inward the inward a higher house URLs, you tin role the next code inward the Spring MVC controller:

@RequestMapping("/orders")
public String showOrderDetails(@RequestParam("id") String orderId, Model model){
   model.addAttribute("orderId", orderId);
   return "orderDetails";
}


If the get upwardly of the query parameter is same every bit the get upwardly of the variable inward handler's @RequestParam annotated declaration too then y'all tin only role @RequestParam without specifying the get upwardly of a query parameter, Spring volition automatically derive the value (see REST URIs contains values e.g. a REST API to holler back a majority using ISBN release looks similar following:

URL: http://localhost:8080/book/9783827319333

Now, to extract the value of ISBN release from the URI inward your Spring MVC Controller's handler method, y'all tin role @PathVariable annotation every bit shown inward next code:

@RequestMapping(value="/book/{ISBN}", method= RequestMethod.GET)
public String showBookDetails(@PathVariable("ISBN") String id,
                              Model model){
   model.addAttribute("ISBN", id);
   return "bookDetails";
}

Similar to @RequestParameter annotation, y'all besides tin besides omit the value attribute inward @PathVariable annotation, if the get upwardly of path variable's placeholder inward the @RequestMapping annotation is same to the variable get upwardly inward the handler method's @PathVariable annotated parameter (see REST amongst Spring).

For example, y'all tin rewrite inward a higher house code every bit shown below:

@RequestMapping(value="/book/{ISBN}", method= RequestMethod.GET)
public String showBookDetails(@PathVariable String ISBN, 
                              Model model){
   model.addAttribute("ISBN", ISBN);
   return "bookDetails";
}


Spring MVC provides several useful annotations to map too extract information from HTTP asking too every bit Spring developer, y'all should last aware of these e.g. @RequestMapping, @RequestParam, too @PathVariable.

These concepts too annotations are really of import from both Spring MVC interview prospect every bit good every bit Spring certifications. You volition ever discovery a couplet of questions based upon these concepts.

Btw, if y'all are preparing for Spring Web Certifications, y'all tin besides banking corporation jibe out David Mayer's gratuitous Spring Mock Questions to acquire an thought virtually the degree of questions too format of questions y'all tin hold off on existent Spring Web Certification.

Difference betwixt @PathVariable too @RequestParam inward Spring

Now that nosotros sympathize both the departure every bit good every bit how to role both @RequestParam too @PathVariable inward Spring MVC application, let's revise the fundamental departure betwixt them from an interview perspective.

1) The @RequestParam is used to extract query parameters piece @PathVariable is used to extract information correct from the URI.

2) @RequestParam is to a greater extent than useful on a traditional spider web application where information is by too large passed inward the query abatements piece @PathVariable is to a greater extent than suitable for RESTful spider web services where URL contains values e.g. http://localhost:8080/book/9783827319333, hither data, which is ISBN release is business office of URI.

If y'all desire to larn to a greater extent than virtually how to effectively educate REST applications using Spring, I advise y'all bring together Eugen Paraschiv's REST amongst Spring course.

It's an online class which volition learn y'all the nitty-gritty of developing both REST API too services for real-world scenarios.

Eugen has extensive experienced inward developing RESTful spider web services using Spring too this class is a slap-up agency to tap into his knowledge.

3) @RequestParam annotation tin specify default values if a query parameter is non acquaint or empty past times using a defaultValue attribute, provided the required attribute is false.

4) Spring MVC allows y'all to role multiple @PathVariable annotations inward the same method, provided, no to a greater extent than than i declaration has the same pattern.


That's all virtually the difference betwixt @PathVariable too @RequestParam in Spring MVC. Even though both are used to extract information from URL, @RequestParam is used to holler back query parameters, anything afterward ? inward the URL, piece @PathVariable is used to holler back values from URI itself.  This concept is really of import for both traditional spider web application evolution every bit good every bit developing RESTful Web Services using Spring, hence y'all must pass exactly about fourth dimension to sympathize it better.

Other Spring MVC articles y'all may similar to explore
Spring Framework 5: Beginner to Guru
Spring MasterClass from Beginner to Expert
Difference between @RestController too @Controller inward Spring MVC?
How Spring MVC plant internally?
What is the role of DispatcherServlet inward Spring MVC?
How to enable Spring safety inward a Java spider web application?
Spring inward Action past times Craig Walls

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