Top X Saltation Mvc In Addition To Residual Annotations Amongst Examples For Coffee Programmers

Hello guys, welcome to my 3rd article on exploring essential annotations from the Spring framework, the most pop framework for Java development. In the get-go article, I accept shared some of the most useful Spring Framework annotations, which were based upon Core Spring functionalities similar dependency injection, inversion of control, as well as configuration, as well as inwards the instant article, nosotros accept learned well-nigh of import Spring Cloud annotations like @EnableConfigServer, @EnableEurekaSever, as well as @EnableDiscoveryClient. Now that y'all know those essential Spring annotations it's fourth dimension to movement towards Spring MVC as well as REST, i of the most used parts of Spring Framework.

In this article, y'all volition larn some of the essential Spring MVC as well as REST annotations similar @Controller, @RequestMapping, as well as @RestController. These annotations are real useful for creating Spring-based Java spider web application as well as RESTful spider web services.

I peculiarly similar Spring MVC's back upward for developing RESTful spider web services inwards Java. As I accept explained inwards my before article 7 reasons to occupation Spring MVC for REST inwards Java, it provides convenient annotations similar @RestController, @ResponseBody, as well as @ResponseStatus to create fully functional REST APIs inwards Java.

In add-on to exploring kernel Spring MVC annotations similar @RequestMapping, @RequestParam, as well as @PathVariable, we'll also explore those which are immensely helpful for developing REST APIs inwards Java.

Btw, if y'all accept worked inwards Spring MVC hence y'all should already accept some basic ideas well-nigh these annotations, but if y'all don't accept whatever prior sense as well as simply started alongside Spring framework as well as Spring MVC hence I propose y'all to get-go acquire through a comprehensive class similar Spring Framework 5: Beginner to Guru class on Udemy.  One of the most useful courses on Spring framework.

10 Spring MVC as well as REST annotations for Java developers

Without wasting whatever to a greater extent than of your time, hither is my listing of some of the must-know Spring MVC as well as REST annotations for Java developers. If y'all accept used Spring MVC to create a spider web application or RESTful applications hence y'all should already hold upward familiar alongside these but if y'all haven't don't worry, you'll larn inwards this article.

Btw, I'll non acquire inwards also much particular well-nigh roofing every unmarried alternative as well as functionality of these annotations, simply to occur this article inwards reasonable length, but volition give y'all resources similar Spring inwards Action mass where y'all tin larn these annotations as well as their occupation inwards depth.

1. @Controller

This annotation is used to brand a class equally spider web controller, which tin handgrip customer requests as well as transportation a reply dorsum to the client. This is a class marking annotation, which is pose on top of your controller class. Similar to @Service as well as @Repository it is also a stereotype annotation. If y'all are wondering what is the departure betwixt them hence y'all tin also come across this article to larn to a greater extent than well-nigh their differences.

Here is an event of @Controller annotation inwards Spring MVC:

@Controller public class HelloController{ // handler methods }

This is a uncomplicated controller class which contains handler methods to handgrip HTTP asking for dissimilar URLs. You don't ask to extend a class or implement an interface to create the controller anymore.

2. @RequestMapping

The Controller class contains several handler methods to handgrip dissimilar HTTP asking but how does Spring map a particular asking to a particular handler method? Well, that's done alongside the assistance of the @RequestMapping annotation. It's a method marking annotation which is specified over a handler method.

It provides the mapping betwixt the asking path as well as handler method. It also supports some advanced alternative which tin hold upward used to specify carve upward handler methods for dissimilar types of asking on the same URI similar y'all tin specify a method to handgrip GET request as well as some other to handgrip POST asking on same URI.

Here is an event of @RequestMapping annotation inwards Spring MVC:

@Controller public class HelloControler{    @RequestMapping("/")   public String hello(){     return "Hello Spring MVC";   } }

In this example, the domicile page volition map to this handler method. So whatever asking comes to the localhost:8080 volition acquire to this method which volition render "Hello Spring MVC".

The value attribute of @RequestMapping annotation is used to specify the URL pattern but if at that spot are no to a greater extent than arguments hence y'all also omit that.

You tin also specify the HTTP method using RequestMethod attribute. If y'all are novel to Spring MVC, I propose y'all acquire through  @RequestParam annotation inwards Spring MVC from my before article well-nigh the departure betwixt RequestParam as well as PathVariable annotation:

@RequestMapping("/book") world String showBookDetails(  @RequestParam("ISBN") String ISBN, Model model){   model.addAttribute("ISBN", ISBN);   render "bookDetails"; }

If y'all access your spider web application which provides mass details alongside a query parameter similar below:

http://localhost:8080/book?ISBN=900848893

hence higher upward handler method volition hold upward called because it is jump to the "/book" URL as well as the query parameter ISBN volition hold upward used to populate the method declaration alongside the same refer "ISBN" within showBookDetails() method.

You tin fifty-fifty occupation a dissimilar refer of your choice. If y'all are interested inwards learning to a greater extent than well-nigh @RequestParam annotation as well as its diverse options hence Spring MVC For Beginners: Build Java Web App inwards 25 Steps on Udemy is a corking house to start with.

4. @PathVariable

This is some other annotation which is used to shout back information from the URL. Unlike @RequestParam annotation which is used to extract query parameters, this annotation enables the controller to handgrip a asking for parameterized URLs similar URLs that accept variable input equally constituent of their path like:

http://localhost:8080/books/900083838

If y'all desire to shout back the ISBN pose out "900083838" from the URL equally method declaration hence y'all tin occupation @PathVariable annotation inwards Spring MVC equally shown below:

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

The Path variable is represented within curly braces similar {ISBN}, which agency the constituent afterward /books is extracted as well as populated on method declaration id, which is annotated alongside @PathVaraible.

In short, this annotation binds placeholder from the URI to a method parameter within the handler method. This is immensely useful land developing RESTful spider web services which contains useful information equally constituent of their URL.

5. @RequestBody

This annotation tin convert inbound HTTP information into Java objects passed into the controller's handler method. Just equally @ResponseBody tells the Spring MVC to occupation a message converter when sending a reply to the client, the @RequestBody annotations tell the Spring to uncovering a suitable message converter to convert a resources representation coming from a customer into an object.

Here is an example:

@RequestMapping(method=RequestMethod.POST, consumers= "application/json") world @ResponseBody Course saveCourse(@RequestBody Course aCourse){    render courseRepository.save(aCourse); }

This is in i trial again a real useful annotation land developing RESTful spider web service inwards Java using Spring framework as well as i of the reasons why I dear to write RESTful API using Spring.

If y'all are also interested inwards developing RESTful application inwards Java hence I propose going through Eugen Parachiv's REST alongside Spring Certification class on Baeldung. He has shared his years of sense inwards developing REST-based applications using Spring inwards this course.

6. @ResponseBody

The @ResponseBody annotation is i of the most useful annotations for developing RESTful spider web service using Spring MVC. This annotation is used to transform a Java object returned from he a controller to a resources representation requested past times a REST client. It tin completely bypass the thought resolution part.

Here is an event of @ResponseBody annotation inwards Spring MVC:

@RequestMapping(method=RequestMethod.POST,consumers= "application/json") world @ResponseBody Course saveCourse(@RequestBody Course aCourse){   render courseRepository.save(aCourse); }

This is the same equally the previous event but the @ResponseBody is used to dot that the reply returned past times this method volition hold upward converted into a resources which the customer tin consume.

If y'all accept created whatever RESTful spider web service alongside Spring MVC hence y'all know that nosotros ask to annotate each method which generates REST reply alongside the @ResponseBody annotation but alongside the introduction of @RestController, nosotros tin avoid this.

7. @RestController

This is convenience annotation for developing RESTful spider web service alongside Spring MVC framework. The @RestController is a combination of @Controller as well as @ResponseBody, which was introduced inwards the Spring 3.4 version.

When y'all annotate a controller class alongside @RestController it does 2 purposes, first, it says that the controller class is treatment a asking for REST APIs as well as instant y'all don't ask to annotate each method alongside the @ResposneBody annotation to signal that the reply volition hold upward converted into a Resource using diverse HttpMessageConverers.

Here is an event of @RestController annotation inwards Spring MVC:

@RestController class HelloControler{  @RequestMapping("/") public String hello(){   return "Hello Spring Booot"; }  }

You tin come across that at that spot is no @ReseponseBody annotation is required to generate RESTful response. Before @RestController, Java developer used @Controller on top of the class as well as annotated each handler method alongside @ResponseBody annotation.

Spring designer saw this as well as brand life easier past times introducing @RestController. If y'all are interested, y'all tin larn to a greater extent than well-nigh it on RESTful Web Services alongside Java as well as Spring, a comprehensive class for developing a existent basis as well as secure REST API alongside Java as well as Spring.
You volition also larn about Implementing API calls, Sign-up, sign-in, e-mail verification, password reset, update, delete as well as fifty-fifty how to deploy RESTFul Java apps on Amazon AWS Cloud.

8. @SprinbBootApplication

This is a relatively novel annotation but real useful if y'all are using Spring Boot for creating Java spider web application alongside Spring. This unmarried annotation combines 3 annotations similar @Configuration, @EnableAutoConfiguration, as well as @ComponentScan. If y'all occupation Spring Boot, hence y'all tin run your application without deploying into a spider web server, equally it comes alongside an embedded Tomcat server.

When y'all annotated your Main class alongside @SpringBootApplication hence it enables Java-based configuration equally good equally ingredient scanning as well as auto-configuration characteristic of Spring Boot, which tin magically prepare things for y'all past times simply dropping the required JAR into classpath.

hither is an event of using @SpringBootApplicaiton annotation inwards Spring:

import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication;  @SpringBootApplication  // same equally @Configuration @EnableAutoConfiguration @ComponentScan public class SpringBootApp{   public static void main(String[] args) {   SpringApplication.run(SpringBootApp.class, args);  }  }

Since Spring Boot provides many features to brand Java evolution alongside Spring easier, I propose y'all to occupation Spring Boot going forward. If y'all are novel to Spring kicking then Spring Boot MasterClass course on Udemy is i of the valuable resources to larn as well as master copy Spring Boot.

9. @EnableAutoConfiguration

This is some other Spring kicking annotation which enables the auto-configuration feature, which makes Spring justice the configuration based on the JAR presents inwards the classpath.

This is genuinely the original annotation which was used to enable/disable auto-configuration, nowadays from the real get-go liberate of Spring Boot. Since it was constantly used alongside @Configuration as well as @ComponentScan on an before version of Spring boot, they accept come upward up alongside a convenience @SpringBootApplication annotation.

Though y'all tin nevertheless occupation @EnableAutoConfiguration annotation if y'all desire to customize or accept some command over auto-configuration.

For example, y'all tin exclude for sure classes from auto-configuration equally shown inwards the next event from my before post well-nigh the departure betwixt @SpringBootApplication as well as @EnableAutoConfiguration inwards Spring boot:

@Configuration @EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class}) public class MyConfiguration {   //.. Java code }

If y'all desire to larn to a greater extent than well-nigh this annotation hence Spring Boot inwards Action past times Craig Walls is i of the best resources to start with.

10. @ResponseStatus

This annotation tin hold upward used to override the HTTP reply code for a response. You tin occupation this annotation for fault treatment land developing a spider web application or RESTful spider web service using Spring. Here is an event of @ResponseStatus inspired past times my favorite Spring inwards Action book:

@Exceptionhandler(BookNotFoundException.class) @ResponseStatus(HttpStatus.NOT_FOUND) public Error bookNotFound(BookNotFoundException bnfe){   long ISBN = bnfe.getISBN();   return new Error(4, "Book [" + ISBN + "] non found"); }

Here nosotros are returning an fault if the mass for given ISBN is non institute inwards our library as well as nosotros accept used @ResponseStatus to override the HTTP condition code equally 404 to dot customer a missing resource.


That's all well-nigh some of the essential Spring MVC as well as REST annotations. As a Java developer, y'all should hold upward familiar alongside these annotations, especially if y'all are using Spring MVC for creating a spider web application or RESTful spider web service inwards Java. If y'all desire to larn to a greater extent than well-nigh these annotations as well as diverse options to configure as well as occupation them, hither are some resources y'all tin consult.

Further Learning
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Thanks for reading this article hence far. If y'all uncovering these Spring MVC annotations useful hence delight portion alongside your friends as well as colleagues on Facebook as well as Twitter. If y'all accept whatever questions or feedback hence delight drib a note.

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