Differences Betwixt @Requestparam As Well As @Pathvariable Annotations Inward Leap Mvc?

The Spring MVC framework, 1 of the most pop frameworks for developing a spider web application inwards Java the world besides provides several useful annotations to extract information from the incoming asking together with mapping the asking to the controller, e.g., @RequestMapping, @RequestParam, together with @PathVariable. Even though both @RequestParam and @PathVariable is used to extract values from the HTTP request, in that location is a subtle departure betwixt them, which makes them a useful inquiry from an interview together with spring certification indicate of view. We'll attempt the subtle departure between @RequestParam together with @PathVaraible inwards this article. As the advert 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 remember a majority on topic "Java" is http://localhost:8080/shop/order/1001/receipts?date=12-05-2017, together with thence you lot tin work the @RequestParam annotation to remember the query parameter date together with you lot tin work @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 the query parameter tin hold upwards optional, but the URL must induce got the same URI.

How to extract Query Parameters inwards Spring MVC using @RequestParam

Spring MVC is a rich framework to prepare both spider web applications together with RESTful spider web services inwards Java. It provides several ways to remember information from the incoming HTTP requests e.g.

• Request Parameters
• Path Variables
• Form inputs

Now that you lot know the departure betwixt @RequestParam together with @PathVariable inwards Spring MVC let's encounter how to write Spring controllers that tin grip asking parameters together with path variables.

Using @RequestParam to acquire Query parameters

In a Spring MVC application, you lot tin work the @RequestParam annotation to convey query parameters inwards Controller's handler methods.

For examples, suppose you lot induce got a spider web application which returns details of orders together with trades, together with you lot induce got the next URLs:

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

To convey the query parameters inwards the to a higher house URLs, you tin work the next code inwards the Spring MVC controller:

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


If the advert of the query parameter is same every bit the advert of the variable inwards handler's @RequestParam annotated declaration together with thence you lot tin only work @RequestParam without specifying the advert of a query parameter, Spring volition automatically derive the value (see REST URIs contains values, e.g. a REST API to remember a majority using ISBN release looks similar the following:

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

Now, to extract the value of ISBN release from the URI inwards your Spring MVC Controller's handler method, you lot tin work @PathVariable annotation every bit shown inwards 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, you lot besides tin besides omit the value attribute inwards @PathVariable annotation, if the advert of path variable's placeholder inwards the @RequestMapping annotation is same to the variable advert inwards the handler method's @PathVariable annotated parameter (see REST amongst Spring).

For example, you lot tin rewrite to 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 together with extract information from the HTTP request, together with every bit of Spring developer, you lot should hold upwards aware of these, e.g. @RequestMapping, @RequestParam, together with @PathVariable.

These concepts together with annotations are telephone substitution from both Spring MVC interview prospect every bit good every bit Spring certifications. You volition ever discovery a distich of questions based on these concepts.

Btw, if you lot are preparing for Spring Web Certifications, you lot tin besides cheque out David Mayer's gratuitous Spring Mock Questions to acquire an thought almost the degree of questions together with format of questions you lot tin human face on existent Spring Web Certification.

Difference betwixt @PathVariable together with @RequestParam inwards Spring

Now that nosotros empathise both the departure every bit good every bit how to work both @RequestParam together with @PathVariable inwards Spring MVC application, let's revise the critical 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 generally passed inwards 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 purpose of URI.

If you lot desire to larn to a greater extent than almost how to effectively prepare REST applications using Spring, I propose you lot bring together Eugen Paraschiv's REST amongst Spring course.

It's an online course of teaching which volition instruct you lot the nitty-gritty of developing both REST API together with services for real-world scenarios.

Eugen has extensive experienced inwards developing RESTful spider web services using Spring, together with this course of teaching is a bully means 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 you lot to work multiple @PathVariable annotations inwards the same method, provided, no to a greater extent than than 1 declaration has the same pattern.


That's all almost the difference betwixt @PathVariable together with @RequestParam in Spring MVC. Even though both are used to extract information from URL, @RequestParam is used to remember query parameters, anything afterward ? inwards the URL, piece @PathVariable is used to remember values from URI itself.  This concept is essential for both traditional spider web application evolution every bit good every bit developing RESTful Web Services using Spring, thence you lot must pass around fourth dimension to empathise it better.

Other Spring MVC articles you lot may similar to explore
Spring Framework 5: Beginner to Guru
Spring MasterClass from Beginner to Expert
Difference between @RestController together with @Controller inwards Spring MVC?
How Spring MVC industrial plant internally?
What is the work of DispatcherServlet inwards Spring MVC?
How to enable Spring safety inwards a Java spider web application?
Spring inwards Action past times Craig Walls

Thanks for reading this article thence far. If you lot similar this article, together with thence delight portion it amongst your friends together with colleagues. If you lot induce got whatsoever questions, delight driblet me a note. 

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