Extras
- parsing json using jackson
  https://mkyong.com/java/jackson-how-to-parse-json/
  [How to parse JSON string with Jackson - Mkyong.com.pdf](../../../../_resources/How%20to%20parse%20JSON%20string%20with%20Jackson%20-%20Mkyong.com.pdf)
  [How to parse JSON string with Jackson - Mkyong.com (22_9_2024 8_29_12 am).html](../../../../_resources/How%20to%20parse%20JSON%20string%20with%20Jackson%20-%20Mkyong.com.html)




  ```java
  
	package com.example.demo;

	import org.springframework.boot.SpringApplication;
	import org.springframework.boot.autoconfigure.SpringBootApplication;
	import org.springframework.boot.json.*;

	import com.fasterxml.jackson.databind.JsonNode;
	import com.fasterxml.jackson.databind.ObjectMapper;


	@SpringBootApplication
	public class DemoApplication {


		public static void main(String[] args) throws Exception{
			SpringApplication.run(DemoApplication.class, args);
			ObjectMapper objectMapper= new ObjectMapper();
			JsonNode obj=objectMapper.readTree("[\"java is oops\", \"java is not oops\", \"java is annoying\"]");
			if(obj.isArray()){
				for(int i=0;i<obj.size();i++){
					System.out.println(obj.get(i).asText());

				}
			}

		}

	}



  ```
 - for json array to `List<String>`
   ```java
	import com.fasterxml.jackson.databind.ObjectMapper;
	List<String> options= objmapper.readValue(q.getOptions(), objmapper.getTypeFactory().constructCollectionType(List.class, String.class));
   ```
 - spring cors
   https://spring.io/guides/gs/rest-service-cors
   ```java
	package com.example.restservicecors;

	import java.util.concurrent.atomic.AtomicLong;

	import org.springframework.web.bind.annotation.CrossOrigin;
	import org.springframework.web.bind.annotation.GetMapping;
	import org.springframework.web.bind.annotation.RequestParam;
	import org.springframework.web.bind.annotation.RestController;

	@RestController
	public class GreetingController {

		private static final String template = "Hello, %s!";

		private final AtomicLong counter = new AtomicLong();
		@CrossOrigin(origins = "http://localhost:9000")
		@GetMapping("/greeting")
		public Greeting greeting(@RequestParam(required = false, defaultValue = "World") String name) {
			System.out.println("==== get greeting ====");
			return new Greeting(counter.incrementAndGet(), String.format(template, name));
		}

	}
   ```
 &nbsp;
 Array.map equivalent in java
 ```java
	 List<Integer> correctOptions = questionsResponses.stream().map(questionsResponse-> questionsResponse.getCorrectOptionNumber()).toList();
```
- converting biginteger into int
 `int questionID = ((BigInteger) questionResponseMap.get("questionID")).intValue();`
 - when using dependency 
   ```xml
	 <dependency>
		    <groupId>org.springframework.boot</groupId>
		    <artifactId>spring-boot-starter-security</artifactId>
   </dependency>
	```
	
 by default it adds authentication layer for accessing rest api, if that is not needed then it can be disabled by adding following bean 
```java
package com.example.demo; // Adjust the package name as needed

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.web.SecurityFilterChain;

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        http
                .authorizeRequests()
                .anyRequest().permitAll() // Allow all requests
                .and()
                .csrf().disable(); // Optionally disable CSRF protection

        return http.build();
    }
}

```
- configure PORT
 https://www.baeldung.com/spring-boot-change-port
 in application.properties
 `server.PORT=8081`