In Spring Boot's reactive programming model, you can efficiently handle streaming of large result sets from a database by using the Flux API provided by Project Reactor. The Flux API allows you to work with reactive streams, which are ideal for handling asynchronous and potentially large datasets. It provides methods for transforming, filtering, and processing data in a non-blocking manner, making it suitable for scenarios where traditional synchronous JDBC calls may not perform efficiently.

The @DataJpaTest annotation is used to test JPA repositories in Spring Boot. It disables full auto-configuration and sets up only the configuration relevant to JPA tests, making it ideal for repository testing.

You can customize the conditions under which a bean is created within a custom Auto Configuration by using the @Conditional annotation and specifying a custom condition class. This condition class can determine when the bean should be created based on your criteria. While @ConditionalOnProperty is a valid annotation for conditional bean creation, it is primarily used at the class level to conditionally enable the entire configuration class, not for individual bean conditions. The other options do not provide a standard way to customize bean creation conditions.

In Spring Security, you can restrict access to specific HTTP methods by configuring the httpMethod attribute within security rules. This allows you to specify which HTTP methods are allowed or denied for a particular URL pattern. The other options are not used to restrict access to HTTP methods in Spring Security, but rather for other purposes, such as defining mappings or custom headers.

CSRF protection customization or disabling is done by modifying the csrf() method in the HttpSecurity configuration, typically by calling disable() or csrfTokenRepository(). While Option 1 is partially correct, it doesn't encompass all customization options. Options 3 and 4 are incorrect.

To optimize the loading of a large dataset, you should implement pagination using the appropriate method in Spring Data JPA. This allows you to retrieve data in smaller chunks, improving performance. Using a non-relational database or increasing memory allocation may not be the best solutions, and optimistic locking is typically used for handling concurrent access but may not directly address performance issues related to large datasets.

In Spring Boot, the application.yaml file is used to define configuration properties in YAML format. YAML is a human-readable data format often preferred for configuration in Spring Boot. While Spring Boot also supports .properties files, they use a different format. Options 3 and 4 are variations of option 1 and do not represent valid Spring Boot configuration file names.

Spring Cloud primarily facilitates building microservices by providing essential tools for service discovery, load balancing, configuration management, and more. It simplifies the development of microservices-based applications.

The Refresh Token's purpose in OAuth2 is to enable the client to obtain a new access token without requiring the user to reauthenticate. It helps maintain the session's continuity by ensuring that the client can access protected resources even after the initial access token expires. The other options are not the primary purposes of the Refresh Token.

The @WebMvcTest annotation in Spring Boot includes, by default, only the beans annotated with @Controller, @ControllerAdvice, @JsonComponent, and Converter beans. It does not include @Component, @Service, and @Repository beans.