Request Controller

What is REST?

How to Do It?

Spring boot as a framework simplifies the development of restful web services without writing boilerplate code. Let's understand how to expose restful web services using spring boot.

Add Required Dependency

The only dependency we need is the following :

With this one dependency, our application is web-enabled and ready to expose the endpoint. This is without the need for manual configuration of the dispatcher servlet, content negotiator, serializer, deserializer, etc.

Add Controller

To handle the web request, we need to have a controller added to the application. Controllers are special beans in the spring framework ecosystem capable of handling HTTP requests. Spring boot provides a special annotation @RestController to mark the class as a controller.

@RestController Annotation

This "annotation" is another example of meta-annotation or convenience annotation like @SpringBootApplication. The @RestController annotation comprises two annotations.

1. @Controller :
   It’s a Spring stereotype annotation similar to @Bean and @Repository and declares the annotated class as an MVC Controller.
2. @ResponseBody :
   A Spring annotation binds a method return value to the web response body. It uses HTTP Message converters to convert the return value to the HTTP response body based on the content type in the request HTTP header.

Expose REST Endpoint

There are four basic HTTP verbs we use in requests to interact with resources in a REST system, and spring boot provides the corresponding annotation for each of those.

These annotations contain parameters that deal with the HTTP request and response. A few key parameters are

• Path :
  An URL path or resource location. For example path for all the employees will be /employees

• Headers :
  The headers of the mapped request, narrowing the primary mapping. Header attributes restrict the scope of the controller method. Request only mapped if each such title is found to have the given value.

  For example :

  will match requests with a Content-Type of "text/html".

• Consumes :
  Narrows the primary mapping by media types that the handler can consume. For example, if your API supports only JSON format as input. It can be restricted using @GetMapping(value = "/employee", consumes="application/json"). It's an array type, meaning you can supply more than one value.

• Produces :
  Narrows the primary mapping by media types that the mapped handler can produce.

Let's apply this knowledge and expose a couple of endpoints.

The @RequestMapping(/employee) on the class applies the mapping the all the handlers. This is convenient as we don't have to repeat the same mapping in all the handler methods. We have two APIs.

• /employee :
  Return all the employees.
• /employee/{id} :
  Return employee with specific id supplied in the path variable.

Response of the above APIs will be :