Spring Boot REST API

Interview Questions on Spring Boot REST API

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REST stands for Representational State Transfer, which uses HTTP protocol to send data from client to server e.g. a book in the server can be delivered to the client using JSON or XML.

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A resource is how data is represented in REST architecture. By exposing entities as the resource it allows a client to read, write, modify, and create resources using HTTP methods DELETE etc.

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REST API uses HTTP methods to perform operations. Some of the HTTP operations which doesn't modify the resource at the server is known as safe operations e.g. GET and HEAD. On the other hand POST, and DELETE are unsafe because they modify the resource on the server.

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REST API uses HTTP methods to perform operations. Some of the HTTP operations which doesn't modify the resource at the server is known as safe operations e.g. GET and HEAD. On the other hand POST, and DELETE are unsafe because they modify the resource on the server.
On the other hand, the POST is not idempotent because if you send multiple POST request, it will result in multiple resource creation on the server, but again, PUT is idempotent if you are using it to update the resource.
Even, multiple PUT request to update a resource on a server will give same end result.

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Yes, REST is Scalable and interoperable. It doesn't mandate a specific choice of technology either at client or server end. You can use Java, C++, Python or JavaScript to create RESTful Web Services and consume them at the client end. I suggest you read a good book on REST API.

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An HttpMessageConverter is that specifies a converter that can convert from and to HTTP requests and responses. Spring REST uses this interface to convert HTTP response to various formats e.g. JSON or XML.
Each HttpMessageConverter implementation has one or several MIME Types associated with it. Spring uses the "Accept" header to determine the content type client is expecting.
It will then try to find a registered HTTPMessageConverter that is capable of handling that specific content-type and use it to convert the response into that format before sending to the client.

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You just need to create an implementation of AbstractHttpMessageConverter and register it using the WebMvcConfigurerAdapter#extendMessageConverters() method with the classes which generate a new type of request/response.

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Yes, REST API should be stateless because it is based on HTTP which is also stateless. A Request in REST API should contain all the details required it to process i.e. it should not rely on previous or next request or some data maintained at the server end e.g. Sessions. REST specification put a constraint to make it stateless and you should keep that in mind while designing your REST API.

Spring Boot REST API

Interview Questions on Spring Boot REST API

What does REST stand for?

What is a resource?

What are safe REST operations?

What are idempotent operations? Why is idempotency important?

Is REST scalable and/or interoperable?

What is an HttpMessageConverter in Spring REST?

How to create a custom implementation of HttpMessageConverter to support a new type of request/responses?

Is REST normally stateless?