Implementing READ operation

In the earlier step, we created blog posts. In this step, we'll implement a read operation and make a call to read blog posts. We'll write two service methods, one for reading a single post and another for multiple posts.

What you need

You need to have the following files obtained from previous steps. You can always download the full version, instead of creating one yourself.

1. Implement server-side

Let's write two methods for retrieving blog posts; one for a single post and another for multiple posts.

In the BlogServiceImpl class, implement the getBlogPost() method to retrieve a single post. Let's throw an exception in case there is no blog post for the given ID.

BlogServiceImpl.java
import example.armeria.blog.thrift.BlogNotFoundException;
...
@Override
public void getBlogPost(GetBlogPostRequest request, AsyncMethodCallback<BlogPost> resultHandler)
        throws TException {
  final BlogPost blogPost = blogPosts.get(request.getId());
  if (blogPost == null) {
    // throwing an exception will also have the same effect
    // throw new BlogNotFoundException("The blog post does not exist. ID: " + request.getId());
    resultHandler.onError(
            new BlogNotFoundException("The blog post does not exist. ID: " + request.getId()));
  } else {
    resultHandler.onComplete(blogPost);
  }
}

2. Implement client-side

This time, we'll implement the client-side for reading blog posts. Let's implement client methods for each corresponding server method.

In the BlogClient class, add a method to retrieve a single post.

BlogClient.java
import example.armeria.blog.thrift.GetBlogPostRequest;
...
BlogPost getBlogPost(int id) throws TException {
  final GetBlogPostRequest request =
              new GetBlogPostRequest().setId(id);
  return blogService.getBlogPost(request);
}

3. Test retrieving a single post

Let's test if we can retrieve a blog post we created.

  1. In the BlogServiceTest class, add a test method to retrieve the first blog post with ID 0.

    BlogServiceTest.java
    @Test
void getBlogPost() throws TException {
  final BlogClient client = new BlogClient(server.httpUri(), "/thrift");
  final BlogPost blogPost = client.getBlogPost(0);

  assertThat(blogPost.getTitle()).isEqualTo("My first blog");
  assertThat(blogPost.getContent()).isEqualTo("Hello Armeria!");
}

  2. Add annotations to configure the order our test methods will be executed. The annotations guarantee that the first blog post will be created in the createBlogPost() method before we try to retrieve it in the getBlogPost() method.

    BlogServiceTest.java
    import org.junit.jupiter.api.MethodOrderer.OrderAnnotation;
import org.junit.jupiter.api.Order;
import org.junit.jupiter.api.TestMethodOrder;

@TestMethodOrder(OrderAnnotation.class) // Add this
class BlogServiceTest {
  ...

  @Test
  @Order(1) // Add this
  void createBlogPost() throws TException {
    ...
  }

  @Test
  @Order(2) // Add this
  void getBlogPost() throws TException {
    ...
  }
}

  3. Run all the test cases on your IDE or using Gradle.

    Your client retrieved a blog post from the server successfully if the test is passed.

4. Test an error case

Let's try retrieving a blog post that does not exist. Add a test method to retrieve a blog post with an invalid ID, asserting an exception is thrown.

BlogServiceTest.java
import static org.assertj.core.api.Assertions.catchThrowable;
import example.armeria.blog.thrift.BlogNotFoundException;
...
@Test
@Order(3)
void getInvalidBlogPost() {
  final BlogClient client = new BlogClient(server.httpUri(), "/thrift");
  final Throwable exception = catchThrowable(() -> {
    client.getBlogPost(Integer.MAX_VALUE);
  });
  assertThat(exception)
    .isInstanceOf(BlogNotFoundException.class)
    .extracting("reason")
    .asString()
    .isEqualTo("The blog post does not exist. ID: " + Integer.MAX_VALUE);
}

Run all the test cases on your IDE or using Gradle. Check that you see the test is passed.

5. Test retrieving multiple posts

Finally, let's test if we can retrieve multiple posts. Add a test method like the following to create the second blog post and test retrieving the list of blog posts.

BlogServiceTest.java
import java.util.List;
...
@Test
@Order(4)
void listBlogPosts() throws TException {
  final BlogClient client = new BlogClient(server.httpUri(), "/thrift");
  client.createBlogPost("My second blog", "Armeria is awesome!");

  final List<BlogPost> blogs = client.listBlogPosts(false);
  assertThat(blogs).hasSize(2);
  final BlogPost firstBlog = blogs.get(0);
  assertThat(firstBlog.getTitle()).isEqualTo("My first blog");
  assertThat(firstBlog.getContent()).isEqualTo("Hello Armeria!");

  final BlogPost secondBlog = blogs.get(1);
  assertThat(secondBlog.getTitle()).isEqualTo("My second blog");
  assertThat(secondBlog.getContent()).isEqualTo("Armeria is awesome!");
}

Run all the test cases on your IDE or using Gradle. Check that you see the test is passed.

What's next

In this step, we've implemented service methods and client methods to retrieve blog posts.

Next, at Step 5. Implement UPDATE, we'll implement an UPDATE operation to update a blog post.

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