20 JAX-RS Interview Questions and Answers

JAX-RS, or Java API for RESTful Web Services, is a popular Java framework used for developing web services. If you are applying for a position that involves Java development, it is likely that you will be asked questions about JAX-RS during your interview. Reviewing common questions and preparing your answers ahead of time can help you feel confident and impress the interviewer. In this article, we discuss the most common JAX-RS questions and how you should respond.

JAX-RS Interview Questions and Answers

Here are 20 commonly asked JAX-RS interview questions and answers to prepare you for your interview:

1. What is JAX-RS?

JAX-RS is a Java API for RESTful web services. It is used to create web services that can be consumed by a variety of clients, including web browsers and mobile devices. JAX-RS is part of the Java EE platform, and as such, it can be used to create both server-side and client-side web services.

2. Can you explain the architecture of a JAX-RS application?

JAX-RS applications are typically built around a central resource class. This resource class contains methods that are annotated with JAX-RS annotations, which define how the resource should be accessed. For example, a resource class might have a method annotated with @GET, which would be invoked when a GET request is made to the corresponding URL. Other methods might be annotated with @POST, @PUT, or @DELETE, depending on the desired functionality.

3. How do you set up and deploy a JAX-RS application?

You can set up and deploy a JAX-RS application using a number of different methods. One popular way is to use a Java EE container, such as Tomcat or Jetty. You can also use a standalone server, such as Grizzly or Undertow.

4. What are some common annotations used in JAX-RS applications?

@Path, @GET, @POST, @PUT, @DELETE, @Produces, @Consumes

5. Why do we need to use HTTP verbs like GET, POST, DELETE etc when building RESTful services with JAX-RS?

The use of HTTP verbs is important when building RESTful services because it helps to create a consistent interface that can be easily understood by both humans and machines. By using the same set of verbs for all of your resources, you make it easier for others to interact with your API and understand how it works. Additionally, using the proper HTTP verb for each action helps to ensure that your API is performing the correct action for each request.

6. Is it possible to add custom headers to requests? If yes, then how?

Yes, it is possible to add custom headers to requests. This can be done by using the @HeaderParam annotation.

7. Can you give me an example of how the @Path annotation is used in a JAX-RS application?

The @Path annotation is used to specify the URI path template to which a resource class or class method will be mapped. For example, if you have a resource class with a method annotated with @Path(“/foo”), then any requests made to /foo will be routed to that method.

8. Can you give me an example of how the @Context annotation is used in a JAX-RS application?

The @Context annotation is used to inject information into a JAX-RS resource. This information can be anything from the request URI to security information. By injecting this information, a JAX-RS resource can be made more flexible and easier to work with.

9. What’s the difference between using or not using the @Produces annotation for a method in a JAX-RS service?

The @Produces annotation is used to specify the media type that a method in a JAX-RS service can produce. If the @Produces annotation is not used, then the method can produce any media type.

10. When would you use interfaces to define resources instead of classes?

You would use interfaces to define resources when you want to create a resource that can be implemented by multiple classes. This would be useful, for example, if you want to create a resource that can be implemented by different classes depending on the situation.

11. How can you parse parameterized paths in URL patterns?

You can use the @PathParam annotation to bind a path parameter to a Java method parameter.

12. Are there any limitations on what data types can be returned from a resource method?

Yes, there are some limitations. A resource method can only return one of the following:
-javax.ws.rs.core.Response
-javax.ws.rs.core.StreamingOutput
-java.io.InputStream
-java.io.Reader

If a resource method returns anything else, then it will need to be wrapped in a javax.ws.rs.core.Response object.

13. What does the @Provider annotation mean in context with JAX-RS?

The @Provider annotation is used to indicate that a particular class is able to provide a certain type of resource. For example, if you have a class that can provide JSON data, you would annotate it with @Provider and specify that it can provide JSON. This is used by JAX-RS to know which classes to look to when it needs to provide a certain type of resource.

14. What is the purpose of the @Consumes annotation?

The @Consumes annotation is used to specify the MIME type(s) that the method can consume.

15. What is the importance of the @ApplicationPath annotation?

The @ApplicationPath annotation is used to define the base URI for all resources in a JAX-RS application. This annotation is required if you want to deploy your application to a Java EE container.

16. What ways are available to create subresources in JAX-RS?

There are a few ways to create subresources in JAX-RS. One way is to use the @Path annotation on a method in a resource class. Another way is to create a new resource class and annotate it with @Path. Finally, you can use a subresource locator to dynamically locate a subresource.

17. Can you name some popular frameworks that support JAX-RS?

Some popular frameworks that support JAX-RS include Apache CXF, Jersey, and Resteasy.

18. What are some best practices to follow while creating REST APIs with JAX-RS?

While there are many different ways to design REST APIs with JAX-RS, there are a few best practices that are worth following:

1. Keep your resource classes and methods small and focused.

2. Avoid using too many @Path annotations.

3. Use @Consumes and @Produces annotations to specify the media types your resource can handle.

4. Use @PathParam and @QueryParam annotations to extract information from the URL.

5. Use @BeanParam to inject all the parameters into a single bean.

6. Use @DefaultValue annotation to provide default values for parameters.

7. Use @MatrixParam annotation to extract information from matrix parameters.

8. Use @HeaderParam annotation to extract information from request headers.

9. Use @CookieParam annotation to extract information from cookies.

10. Use @FormParam annotation to extract information from form parameters.

19. What are some tools that can help test JAX-RS implementations?

There are a few different tools that can help test JAX-RS implementations, such as the JAX-RS Client API and the JAX-RS Test Framework. The Client API can be used to write test cases that invoke JAX-RS services, while the Test Framework provides a set of utilities and mock objects that can be used to test the implementation itself.

20. What is your opinion on the future of JAX-RS?

JAX-RS is a specification for implementing RESTful web services in Java. It is very popular and widely used, and I believe it has a bright future.