M04 Q23 What are the examples of @Conditional annotations? How are they used?

Spring Boot supports following Conditional Annotations for AutoConfiguration classes:

• ConditionalOnBean – presence of Spring Bean
• ConditionalOnMissingBean – absence of Spring Bean
• ConditionalOnClass – presence of class on classpath

• ConditionalOnMissingClass – absence of class on classpath
• ConditionalOnCloudPlatform – if specified cloud platform is active – for example Cloud Foundry
• ConditionalOnExpression – if SpEL expression is true
• ConditionalOnJava – presence of Java in specified version

• ConditionalOnJndi – if JNDI location exists
• ConditionalOnWebApplication – if a web application that uses WebApplicationContext or StandardServletEnvironment
• ConditionalOnNotWebApplication – application that is not a web application
• ConditionalOnProperty – presence of spring property

• ConditionalOnResource – presence of resource
• ConditionalOnSingleCandidate – only one candidate for the bean found

@Conditional annotations are used together with Auto Configuration Classes, to indicate under which conditions, specific @Configuration class should apply.