==========================================
application.properties vs application.yml
==========================================

In Spring Boot, configuration files are used to define settings like below

		1) port number

		2) database connection 

		3) log levels etc.

==============================
📘 application.properties
==============================

=> Represents data in simple key-value format
=> Each property will be there in new line

✅ Pros:

=> Easy to read and write for simple configurations

=> Widely used in java applications

=> Good for flat configurations

❌ Cons:

=> Gets messy for complex or nested configurations

=> Duplicate keywords

=> Support only for java applications

=> Not ideal for structured data like lists or maps

Ex : 

server.port=8080
spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=pass


Note: application.yml is an alternate for application.properties file

====================
📒 application.yml
====================

=> YAML format

=> Supports hierarchical/nested configuration

✅ Pros:

=> Clean and readable, especially for nested properties

=> Better organization of related settings

=> Preferred for complex configurations (like multiple datasources, profiles, mail settings)

=> Supported by multiple programming languages.


❌ Cons:

=> Indentation errors

=> Might be tricky for beginners who are unfamiliar with YAML

Ex:

server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb
    username: root
    password: pass


===========================================
How to read yml file data into java class
===========================================

=> @Value annotation is used to read the data from a yml or properties file based on key

      @Value("${app.messages.greet}")
      private String greetMsg;

=> If we want to read all yml properties at a time into java class object then we can use @ConfigurationProperties(prefix="app") annotation.

```
spring:
  application:
    name: 16-REST-API
    
app:
  messages:
    greet: Good Mrng..!!
    welcome: Welcome to Ashok IT
    invalidLogin: Invalid Credentials
    regSuccess: Registration Successful
    invalidEmail: Email Invalid

```
@Data
@Component
@ConfigurationProperties(prefix="app")
public class AppProperties {

  private Map<String, String> messages = new HashMap<>();

}
```
@RestController
@RequestMapping("/api")
public class MsgRestController {

  @Value("${app.messages.greet}")
  private String greetMsg;

  @Autowired
  private AppProperties appProps;

  @GetMapping(value = "/greet", produces = "text/plain")
  public String getGreetMsg(@RequestParam("name") String name) {

    String msg = name + ", " + greetMsg;

    return msg;
  }

  @GetMapping(value = "/welcome/{name}", produces = "text/plain")
  public ResponseEntity<String> getWelcomeMsg(@PathVariable String name) {

    Map<String, String> messages = appProps.getMessages();

    String welcomeMsg = messages.get("welcome");

    String msg = name + ", " + welcomeMsg;

    return new ResponseEntity<>(msg, HttpStatus.OK);
  }
}
```