In this section, we're going to take a look at how to implement a REST resource using basic JAX-RS annotations. I'll show you how you can inject and use CDI beans in your JAX-RS resource implementation and show you how to properly use HTTP methods to model CRUD semantics, and of course we'll be running the web service within a Docker container:

We'll implement a REST API to get a list of books so that we'll be able to create new books, get a book by ISBN, update books, and delete a book.

We will create a basic project skeleton and prepare a simple class, which is called BookResource, and we will use this to implement the CRUD REST API for our books. So first up, we need to annotate our class using the proper annotations. We will use the @Path annotation to specify the path for our...

In this section, we're going to take a look at how to implement simple sub-resource locator methods. We'll have a look at how you can obtain CDI sub-resource instances from the root resource, and we're going to have a look at how you can pass context information from the root to the sub-resources:

Books have authors, and they can be lent out. In this section, what we'll do is provide specific REST endpoints to obtain the author of a book and the loan details of the books. We have prepared the skeleton of the project, as shown in the following screenshot:

Let's start with the authors. In BookResource.java, add a resource locator method. A resource locator method is a simple method that is only annotated using the @Path annotation. In this case, we use @Path("/{isbn}/author"). The return type...

In this section, we're going to take a look at handling user and server-side errors in a RESTful way by using an appropriate HTTP status code, for example, HTTP status code 400 Bad Request for invalid and malformed requests, status 404 Not Found if something could not be found, and HTTP status code 500 Internal Server Error if something happens unexpectedly. We'll also see how to use WebApplicationException and its subclasses to model error handling, and finally we'll be implementing a custom ExceptionMappers to handle runtime exceptions and return custom error responses:

This is what we'll do conceptually in this section: we'll again extend our library microservice by several HTTP status codes , for example, HTTP 400 if you issue an invalid book update, 409 for creating an already existing book...

In this section, we're going to take a look at the JAX-RS client APIs and how to implement web service clients. I'm going to show you how you can set up and configure a JAX-RS client instance. We'll use WebTarget and its builder to specify request behavior, resolve URI template parameters, do invocation in response handling, and use GenericType implementations to get unmarshalled typed collections:

So far, we've implemented our small library service, which supports books, authors, and loans, via a REST API. We'll then implement a library client which is a standalone client to get a list of books, unknown books, to create books, to get books with the returned URI, and so forth.

Let's switch to our IDE. We will create a small class called LibraryServiceClient, which is...

In this section, we're going to take a look at different test strategies for Java EE 8 web services. We'll talk about testing simple CDI components with plain unit tests and mocks, testing REST resources using the Jersey Test Framework, and we'll see how to do black box integration testing using the Test Containers framework.

So far, we've implemented our library service by offering a REST API for books, authors, and loans. We also implemented the library client. In this section, we'll talk about testing. You can see the test pyramid in the following diagram. At the bottom, there are unit tests. The middle layer is the service layer tests.

At the top level, you have UI layer tests. Unit testing in Java EE is really simple; you can use your standard test frameworks such as JUnit testing, and you may use Mojito or other mocking...

Let's summarize what we learned in this chapter. We had a look at basic JAX-RS annotations in order to implement a REST API with CRUD functionality. We used top resource locators to nicely model nested REST APIs. We used HTTP status codes and exception mappers for error handling. We implemented web service clients using the JAX-RS service client API. Finally, we had a look at testing Java EE 8-based web services using several approaches. I hope you enjoyed this chapter. In the next chapter, we will talk about content marshaling with JSON-B and JSON-P.