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

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+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`
+