Spring Boot Configuration Metadata and Properties Quiz

Spring Boot Configuration Metadata

• Spring Boot jars include metadata files that provide details of all supported configuration properties.

• The metadata files are designed to let IDE developers offer contextual help and "code completion" as users are working with application properties or application.yml files.

• The majority of the metadata file is generated automatically at compile time by processing all items annotated with @ConfigurationProperties.

• Configuration metadata files are located inside jars under META-INF/spring-configuration-metadata.json.

• The metadata files use a JSON format with items categorized under either "groups" or "properties" and additional values hints categorized under "hints".

• Each "property" is a configuration item that the user specifies with a given value.

• The "groups" are higher level items that do not themselves specify a value but instead provide a contextual grouping for properties.

• "Hints" are additional information used to assist the user in configuring a given property.

• The metadata can provide additional information such as deprecation notices, valid values, and providers.

• You can easily generate your own configuration metadata file from items annotated with @ConfigurationProperties by using the spring-boot-configuration-processor jar.

• The jar includes a Java annotation processor which is invoked as your project is compiled.

• If you are using AspectJ or Lombok in your project, you need to make sure that the annotation processors run in the correct order.Spring Boot Configuration Properties

• Processor dependency allows for classes and methods annotated with @ConfigurationProperties to be picked up by the processor.

• If a class has a single parameterized constructor, one property is created per constructor parameter, unless the constructor is annotated with @Autowired.

• If the class has a constructor annotated with @ConstructorBinding, one property is created per constructor parameter for that constructor.

• Properties are discovered through the presence of standard getters and setters with special handling for collection and map types.

• The annotation processor also supports the use of the @Data, @Value, @Getter, and @Setter lombok annotations.

• The Javadoc on fields is used to populate the description attribute of properties.

• Default values have to be provided statically and cannot be detected for Enums and Collections.

• Manual metadata should be provided for cases where the default value could not be detected.

• Inner classes are automatically considered as nested properties.

• The @NestedConfigurationProperty annotation can be used on a field to indicate that a regular class should be treated as if it were nested.

• The annotation processor automatically merges items from additional-spring-configuration-metadata.json into the main metadata file to support custom "hints".

• The additional-spring-configuration-metadata.json file has the same format as the regular spring-configuration-metadata.json file and is optional.