To conditionally process a configuration class based on the presence of a certain bean, you can use the @ConditionalOnBean annotation. This annotation ensures that the configuration class is only processed if the specified bean is present in the ApplicationContext. It's a powerful way to control the activation of configuration based on runtime conditions.

In Spring Boot, you can conditionally enable caching by using the @ConditionalOnProperty annotation with the property name as "spring.cache.enabled." This annotation allows caching to be enabled only when the specified property is set to true. The other annotations do not provide conditional caching based on a property.

Spring Boot provides the MockMvc class, which allows you to simulate HTTP requests and responses for testing controller methods without the need to start a server. It's a crucial tool for integration testing in Spring Boot.

The correct annotation to handle exceptions globally across the entire Spring Boot application is @ControllerAdvice. This annotation allows you to define global exception handlers that can be applied to multiple controllers. It's a powerful tool for managing exceptions consistently throughout your application. The other options are not used for this purpose.

The primary role of the UserDetailsService in Spring Security is to load user details (including username, password, and roles) from a data store, typically a database. It's a fundamental component used for authentication and authorization, as it provides the necessary user information for the security framework to make access control decisions. The other options describe tasks related to authentication and authorization but are not the primary role of UserDetailsService.

The primary responsibility of an OAuth2 Authorization Server in a Spring Boot application is to authenticate users and grant access tokens to authorized clients. It does not store user passwords but rather validates user credentials and authorizes access to protected resources. It also does not manage user profiles and preferences, nor does it control database access; these are typically the tasks of the application's authentication system and database itself.

To optimize the performance of Spring Data JPA when dealing with large datasets, using PagingAndSortingRepository is recommended to read the datasets in chunks. This repository interface extends CrudRepository and provides methods for pagination and sorting, making it suitable for efficiently fetching and processing large datasets by breaking them into manageable chunks.

To customize access-denied behavior, you should implement a custom AccessDeniedHandler, which allows you to define how to handle access-denied situations. You then register this handler with Spring Security to apply it to secured methods.

In Spring Boot reactive programming, the map method is used to transform the items emitted by a Publisher. The map operation allows you to apply a function to each item emitted by a Publisher and produce a new Publisher with the transformed items. This is a common operation when working with reactive streams to perform data transformations.

In Spring Boot, the properties defined in the application.yml file are used to configure the application. While you can also use application.properties, YAML configuration files are a popular choice due to their readability and ease of use for defining properties.