Programmatically adding beans to the Spring context

This project is based on chapter 2.2.3. Programmatically adding beans to the Spring context from book Spring Starts here (2021) by Laurentiu Spilca.

Create Maven project with Intellij Idea

File > New project > Java

Create entity class

public class Book {
    private final String title;

    public Book(String title) {
        this.title = title;
    }

    public String getTitle() {
        return title;
    }

    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj == null || obj.getClass() != this.getClass()) {
            return false;
        }
        Book book = (Book) obj;
        return title == book.title || (title != null && title.equals(book.title));
    }

    public int hashCode() {
        return title == null ? 0 : title.hashCode();
    }
}

Add Spring Context dependency

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>6.1.10</version>
</dependency>

Create Spring context

ApplicationContext context = new AnnotationConfigApplicationContext();

Register bean in Spring context

context.registerBean(Book.class, "The Hunger Games");

Refresh Spring context

context.refresh();

Get bean from Spring context

System.out.println("The book's title is " + context.getBean(Book.class).getTitle());

Add tests

Add dependency for Spring TestContext Framework

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>6.1.10</version>
    <scope>test</scope>
</dependency>

Add dependency for JUnit

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>5.11.0-M2</version>
    <scope>test</scope>
</dependency>

Create test to check that application context is created

public class ApplicationTests {

    @Test
    @DisplayName("Checks that Application Context is created")
    public void checkApplicationContextCreated() {
        ApplicationContext context = new AnnotationConfigApplicationContext();

        assertNotNull(context);
    }
}

Create test to check that bean is registered in the context

public class BookTests {

    @Test
    @DisplayName("Checks that Book is added to the context")
    public void checkBookAddedToContext() {
        GenericApplicationContext context = new AnnotationConfigApplicationContext();
        context.registerBean(Book.class, "The Hunger Games");
        context.refresh();

        Book book = context.getBean(Book.class);

        assertEquals(new Book("The Hunger Games"), book);
    }
}