joplin-notes/joplin notion extension/Web Development/Java/Spring/Extras.md

Extras

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

  
    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>

   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

   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));
   	}
  
   }
  

  Array.map equivalent in 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

    <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

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