The primary purpose of Auto Configuration in Spring Boot is to reduce application complexity. It achieves this by automatically configuring application components based on dependencies and classpath settings. This simplifies the development process by eliminating much of the manual configuration that would otherwise be required. While security, database access, and network connections are important aspects of an application, they are not the primary focus of Auto Configuration.

The process of supplying an external dependency to an object in Spring is called "Dependency Injection." It involves injecting or providing the required dependencies to an object rather than having the object create them itself, promoting loose coupling and easier testing.

The primary purpose of using TestContainers in Spring Boot is to create lightweight, isolated Docker containers for testing. This allows you to run tests in an environment that closely resembles your production environment and is especially useful for testing database interactions.

In Spring Boot, you can define hierarchical properties in a YAML configuration file using YAML nesting. YAML allows you to structure your configuration data hierarchically, making it easy to organize and manage complex configuration settings for your application. This helps in maintaining a clean and readable configuration.

Optimizing a Spring Boot application for faster startup times involves strategies like minimizing the number of auto-configured beans, using lazy initialization for non-essential components, and optimizing classpath scanning. These approaches reduce the initial overhead and improve startup times. The other options, such as increasing auto-configured beans or increasing thread pool size without consideration, can lead to performance issues or longer startup times.

To customize the response body of a global exception handler method in Spring Boot, the method should return an object of type ResponseEntity. This allows you to create a custom response with specific status codes, headers, and response bodies when an exception is caught globally. It provides flexibility in crafting error responses tailored to your application's needs.

In Spring Boot, to perform integration testing and enable full application context loading, you use the @SpringBootTest annotation. This annotation loads the entire Spring application context, making it suitable for integration testing scenarios.

To conditionally exclude specific Auto Configurations, you can use the spring.autoconfigure.exclude property in your application.properties or application.yml file. This property allows you to specify the fully qualified names of the Auto Configuration classes you want to exclude. The other options do not provide a direct way to conditionally exclude Auto Configurations.

The @WebMvcTest annotation is used to load only the Web layer of the Spring application context, making it suitable for testing controllers and related components.

When configuring an OAuth2 Resource Server in Spring Boot, the public_key_location property is used to specify the location of the public key for verifying JWT signatures. This key is essential for validating the authenticity and integrity of JWT tokens used for authentication and authorization. The other options are not typically used for specifying the public key location.

In Spring Boot, the @ReactiveController annotation is used to denote a reactive programming model in a controller. This annotation is specifically designed for reactive programming, and it's part of the Spring WebFlux framework, which enables reactive and non-blocking programming. It's used to define controllers that handle asynchronous and reactive operations.

The main purpose of JSR-303 Bean Validation in Spring Boot is to validate data input and ensure it meets specified criteria. It helps maintain data integrity by checking that the data conforms to the desired constraints and annotations. While Spring Boot is versatile and can handle other tasks, validation is a key function of JSR-303.