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IoC CONTAINER is a framework for implementing automatic DEPENDENCY INJECTION. It manages OBJECT creation and its life-time and also injects dependencies into the class.

You can define both application and Spring boot-related PROPERTIES into a file called application.properties. You can create this file manually or USE Spring Initializer to create this file. You don’t need to do any SPECIAL configuration to instruct Spring Boot to load this file, If it exists in classpath then spring boot automatically loads it and configure itself and the application code ACCORDINGLY.

Debugging logs can be enabled in three ways -

• We can start the APPLICATION with --DEBUG switch.
• We can set the LOGGING.level.ROOT=debug property in application.property file.
• We can set the logging level of the root logger to debug in the SUPPLIED logging configuration file.

Spring BOOT actuator “/ENV” RETURNS the list of all the environment PROPERTIES of RUNNING the spring boot application.

SPRING BOOT actuator “/Beans” is used to GET the LIST of all the spring beans in your application.

ACTUATORS PROVIDE below pre-defined ENDPOINTS to MONITOR our APPLICATION -

• Health
• Info
• Beans
• Mappings
• Configprops
• Httptrace
• Heapdump
• Threaddump
• Shutdown

To ENABLE the spring actuator feature, we NEED to add the DEPENDENCY of “spring-boot-starter-actuator” in pom.xml.

An actuator is an additional feature of Spring that helps you to monitor and manage your APPLICATION when you PUSH it to production. These actuators include auditing, HEALTH, CPU usage, HTTP hits, and metric GATHERING, and many more that are automatically applied to your application.

While developing the application we deal with multiple environments such as dev, QA, PROD, and each ENVIRONMENT requires a different CONFIGURATION. For eg., we might be using an embedded H2 database for dev but for prod, we might have proprietary Oracle or DB2. Even if DBMS is the same across the environment, the URLS will be different.

To make this EASY and clean, Spring has the provision of Profiles to keep the separate configuration of environments.

RequestMapping can be used with GET, POST, PUT, and many other request methods using the method attribute on the ANNOTATION. Whereas getMapping is only an EXTENSION of RequestMapping which helps you to improve on CLARITY on request.

On a high-level spring BOOT APPLICATION follow the MVC pattern which is depicted in the below flow diagram.

@Controller MAP of the model object to VIEW or template and make it human READABLE but @RestController simply returns the object and object data is DIRECTLY WRITTEN in HTTP response as JSON or XML.

It is a combination of @CONTROLLER and @ResponseBody, used for CREATING a restful controller. It converts the response to JSON or XML. It ENSURES that data RETURNED by each method will be written straight into the response body instead of returning a template.

You can USE EXCLUDE ATTRIBUTE of @EnableAutoConfiguration if you WANT auto-configuration not to apply to any specific class.

YES, we can use application.properties to CONFIGURE the WEB application TYPE i.e spring.main.web-application-type=none.

YES, we can replace the Embedded Tomcat server with any server by using the Starter DEPENDENCY in the pom.xml file. LIKE you can use spring-boot-starter-JETTY as a dependency for using a jetty server in your PROJECT.

The DEFAULT PORT of the TOMCAT server-id 8080. It can be CHANGED by adding sever.port properties in the application.property file.

YES, it is POSSIBLE. By USING the server.port in the application.properties.

Yes, we can create a non-web application by removing the web dependencies from the classpath along with CHANGING the WAY SPRING BOOT creates the application context.

Spring Boot dependency MANAGEMENT is used to MANAGE DEPENDENCIES and configuration automatically WITHOUT you SPECIFYING the version for any of that dependencies.

The primary annotations that Spring BOOT offers reside in its org.springframework.boot.autoconfigure and its sub-packages. Here are a couple of basic ones:

@EnableAutoConfiguration – to MAKE Spring Boot LOOK for auto-configuration beans on its classpath and automatically APPLY them.

@SpringBootApplication – USED to denote the main class of a Boot Application. This annotation combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations with their default attributes.