Modern Spring from Scratch: Basics to Core Spring Mastery

Explore inversion of control and dependency injection, contrasting service locator with true inversion of control to reduce coupling and improve testing in large applications.

Explore dependency injection through a chip analogy, showing inversion of control where the order service declares a dependency on the payment service and is supplied via a constructor argument.

Explore how dependency injection decouples services by passing real or mock implementations to the order service, enabling testable, modular code, with the Spring container handling wiring and inversion of control.

Demonstrates replacing manual object creation with Spring dependency injection, using a Spring container and beans, annotated components, configuration and component scanning, and retrieving beans via the application context.

Explore how Spring manages dependency injection by wiring Spring beans through the container, using constructor arguments, and avoiding hard coded dependencies for complex interdependent classes.

Understand the anatomy of a Spring application by distinguishing data holders from service classes, and see how Spring creates a singleton container of wired beans.

Explore how the Spring IoC container uses the framework beans and framework context to manage beans, wire dependencies, and handle lifecycles.

Explore how the Spring application context maintains a bean registry of all beans from configuration, exposes them with getBean, and explains singleton behavior versus self-created instances.

Explore inversion of control and dependency injection in spring, covering constructor and setter based injection, how the container wires beans, and how annotation configuration handles constructor ambiguity.

Explore setter injection as an alternative to constructor injection in Spring, wiring dependencies via setter methods annotated with @Autowired, showing multi-setter support and timing after object creation.

Explore how the application context resolves dependencies, runs the dependency resolution process, manages bean creation and initialization, and handles circular references with setter versus constructor injection and autowiring.

Prefer constructor injection to keep objects fully initialized with mandatory dependencies. Use setter injection for optional or many dependencies, or to break circular dependencies.

Explore optional dependencies in Spring by contrasting constructor injection with setter injection. Make dependencies optional using @Autowired(required=false) and guard with conditional logic when absent.

Examine field injection, injecting directly into a field with autowire via reflection, and learn why constructors are preferred for mandatory dependencies.

Learn how optional dependencies enable modular Spring applications by gracefully handling missing jars, using setter injection with optional flag, and performing null checks to avoid null pointer exceptions.

Explore dependency wiring in Spring using Java config, transforming bean creation with configuration classes and @Bean methods, while comparing annotations and xml approaches and showing a practical demo.

Convert a no-arg bean to Java config, using constructor or setter injection, and reuse the hello world message by passing it as a bean argument for a singleton.

Use Java config with @Configuration and @Bean to define beans in a configuration class. Spring container runs methods at context initialization, injects the returned beans, and resolves dependencies by type.

Assess the benefits of Java config over XML, highlighting type safety that prevents injecting the wrong bean type. Experience programmatic flexibility by writing Java code with annotations and Spring Expression Language, gaining more power and flexibility than XML.

Discover how Spring initializes beans eagerly at startup by default. Use @Lazy to delay bean creation until first use in Java or annotation config.

Discover how lazy and eager beans interact, why dependencies trigger eager initialization, and how context completion shapes initialization order and singletons.

Audience questions explain why field injection is discouraged due to encapsulation concerns and reflection-based injection, contrast with constructor injection, and discuss lazy initialization's startup impact in microservices.

Explore how Spring uses configuration and component scanning to create and manage beans through a bean registry in an application context, and examine singleton-by-default behavior and stateful versus stateless beans.

explore how spring beans default to singleton scope and how to switch to prototype using the scope annotation, creating a new bean per request whether by lookup or injection.

Explore web scopes such as request, session, and application, and how they differ from desktop singleton and prototype in Spring, with Spring MVC managing bean lifecycles.

This lecture explains how autowiring by type can fail when multiple beans implement the same interface, causing ambiguity in dependency injection, and explores interface and inheritance scenarios.

Use qualifiers to distinguish multiple beans of the same type by naming each one and injecting by that name. Learn how @Qualifier and by-name injection resolve conflicts, with @Primary for a default.

Designate a default bean with the @Primary annotation for autowiring by type, and learn how qualifiers override it to safely add new beans without breaking references.

Understand how Spring creates beans in dependency order, ensuring message precedes greeter, while independent beans like Hello world and Hey world have no defined order unless you enforce one.

Learn to control Spring beans initialization order with the depends on annotation, illustrated by two task beans where task B initializes before task A.

Learn how depends on controls the bean initialization order, while the order annotation governs the order of beans in a collection, demonstrated with a list of task beans.

Explore the Spring bean lifecycle from creation to destruction, including scope variations and lifecycle callbacks with post construct and pre destroy to initialize resources and clean up.

Explore life cycle callbacks in spring by using post construct to initialize after dependency injection, compare constructors versus initialization, and understand pre destroy before a bean is destroyed.