SpringContext @AliasFor Anotasyonu

Giriş

Şu satırı dahil ederiz

import org.springframework.core.annotation.AliasFor;

Bir açıklama burada

SpringScheduling Shedlock KeepAliveLockProvider Sınıfı

Giriş

Şu satırı dahil ederiz

import net.javacrumbs.shedlock.support..KeepAliveLockProvider;

Açıklaması şöyle

KeepAliveLockProvider extends the lock in the middle of the lockAtMostFor interval. For example, if the lockAtMostFor is 10 minutes the lock is extended every 5 minutes for 10 minutes until the lock is released. Please note that the minimal lockAtMostFor time supported by this provider is 30s. The scheduler is used only for the lock extension, single thread should be enough.

Örnek

Şöyle yaparız

@Configuration
public class ShedlockConfiguration {

  @Bean
  public LockProvider lockProvider(DataSource dataSource) {
    return new KeepAliveLockProvider(
      getJdbcTemplateLockProvider(dataSource),
      Executors.newSingleThreadScheduledExecutor()
    );
  }

  private JdbcTemplateLockProvider getJdbcTemplateLockProvider(DataSource dataSource) {
    return new JdbcTemplateLockProvider(
      JdbcTemplateLockProvider.Configuration.builder()
        .withJdbcTemplate(new JdbcTemplate(dataSource))
        .withDbUpperCase(true)
        .usingDbTime()
        .build()
      );
  }
}

SpringData ElasticSearch ReactiveElasticsearchClient Arayüzü

Giriş

Şu satırı dahil ederiz 

import org.springframework.data.elasticsearch.client.reactive.ReactiveElasticsearchClient;

Örnek

Şöyle yaparız

@Configuration
public class ReactiveRestClientConfig extends AbstractReactiveElasticsearchConfiguration {
  @Override
  public ReactiveElasticsearchClient reactiveElasticsearchClient() {
    ClientConfiguration clientConfiguration = ClientConfiguration.builder()
      .connectedTo("localhost:9200")
      .build();
    return ReactiveRestClients.create(clientConfiguration);
  }
}

SpringWebFlux Mono.thenReturn metodu

Giriş

İş bittikten sonra farklı bir sonuç dönmek içindir

Örnek

Şöyle yaparız

@Override
public Mono<String> deleteStudent(String id) {
  return studentRepository.deleteById(id)
    .thenReturn("Student deleted successfully!");
}

Spring Amqp RabbitMQ Dead Letter Queue

Örnek

Şöyle yaparız

@Configuration
public class RabbitMQConfig {
  public static final String QUEUE_NAME = "queue-name";
  public static final String DLQ_NAME = "dlq-name";
  public static final String DLX_NAME = "dlx-name";

  @Bean
  public DirectExchange directExchange() {
    return new DirectExchange(DIRECT_EXCHANGE);
  }
  @Bean
  public Queue queue() {
    return new Queue(QUEUE_NAME, true); // Declare the queue as durable
  }
  @Bean
  public Binding binding() {
    return BindingBuilder.bind(queue()).to(directExchange()).with(QUEUE_NAME);
  }

  // DLQ create
  @Bean
  public Queue deadLetterQueue() {
    return new Queue(DLQ_NAME, true); // Declare the DLQ as durable
  }
  @Bean
  public DirectExchange deadLetterExchange() {
    return new DirectExchange(DLX_NAME);
  }
  @Bean
  public Binding deadLetterBinding() {
    return BindingBuilder.bind(deadLetterQueue())
      .to(deadLetterExchange()).with(DLQ_NAME);
  }
  @Bean
  public Binding queueToDeadLetterExchangeBinding() {
    return BindingBuilder.bind(queue())
      .to(deadLetterExchange()).with(QUEUE_NAME);
  }
}

Şöyle yaparız. Burada DLQ'ya kodla gönderiliyor.

@RabbitListener(queues = "queue-name")
public void handleMessage(String message) {
  try {
    // Process the incoming message
    if (someCondition) {
      throw new Exception("Simulated exception");
    }
    // Message processing succeeded
  } catch (Exception e) {
    // Handle the exception or log it
    System.err.println("Error processing message: " + e.getMessage());
            
    // Send the message to the DLQ
    rabbitTemplate.send("direct.exchange", "dlq-name", new Message(message.getBytes()));
  }
}

SpringData JPA ScrollAPI

Giriş

ScrollAPI aslında Spring Data Commons ile geliyor. SpringData JPA bu bağımlılığı getirdiği için bir şey yapmaya gerek yok

Offset-based scrolling

OffsetScrollPosition  veya WindowIterator sınıfı ile kullanılır. Açıklaması şöyle

Offset scrolling works like pagination, which returns expected results by skipping a certain number of records from a large result. While we only see a portion of the requested results, the server needs to build the full result, which causes additional load.

Örnek

Şöyle  yaparız. Ben sadece bazı açıklamalar ekledim. Window sınıfı offsetleri takip ediyor. Kullanım olarak Window sınıfı Iterator gibi. Window.hasNext() çağrısı yapmak lazım

public List<BookReview> getBooksUsingOffset(String rating) {
  // To keep track of the position in the result set.
  OffsetScrollPosition offset = ScrollPosition.offset();

  // Retrieves the first 5 books with the specified rating
  Window<BookReview> bookReviews = bookRepository.findFirst5ByBookRating(rating, offset);
  List<BookReview> bookReviewsResult = new ArrayList<>();
  do {
    // Adds each BookReview to result
    bookReviews.forEach(bookReviewsResult::add);
    // Retrieves the next batch of 5 books with the specified rating
    bookReviews = bookRepository
      .findFirst5ByBookRating(
        rating, 
        (OffsetScrollPosition) bookReviews.positionAt(bookReviews.size() - 1));
  } while (!bookReviews.isEmpty() && bookReviews.hasNext());

   return bookReviewsResult;
}

Örnek

Şöyle  yaparız.   WindowIterator + OffsetScrollPosition  kullanılır. Window.hasNext() çağrısı yapmaya gerek yok

public List<BookReview> getBooksUsingOffSetFilteringAndWindowIterator(String rating) {
  WindowIterator<BookReview> bookReviews = WindowIterator.of(position -> 
    bookRepository
      .findFirst5ByBookRating("3.5", (OffsetScrollPosition) position))
      .startingAt(ScrollPosition.offset());

  List<BookReview> bookReviewsResult = new ArrayList<>();
  bookReviews.forEachRemaining(bookReviewsResult::add);

  return bookReviewsResult;
}

Keyset-Filtering

Açıklaması şöyle. WindowIterator + KeysetScrollPosition  kullanılır

Keyset filtering helps the retrieval of a subset of results using the built-in capabilities of the database aiming to reduce the computation and IO requirements for individual queries.

The database only needs to construct smaller results from the given keyset position without materializing a large full result

Örnek

Şöyle yaparız

public List<BookReview> getBooksUsingKeySetFiltering(String rating) {
  WindowIterator<BookReview> bookReviews = WindowIterator.of(position -> 
    bookRepository
      .findFirst5ByBookRating(rating, (KeysetScrollPosition) position))
      .startingAt(ScrollPosition.keyset());
    
  List<BookReview> bookReviewsResult = new ArrayList<>();
  bookReviews.forEachRemaining(bookReviewsResult::add);

  return bookReviewsResult;
}

Neural Autonomic Transport System (NATS) Kullanımı

Giriş

Açıklaması şöyle

History and Evolution

NATS was originally created by Derek Collison, who, inspired by his experiences with building messaging systems, aimed to craft a messaging solution that embodies simplicity and performance. Over time, as cloud architectures grew in popularity, NATS emerged as a popular choice, primarily because of its inherent characteristics that matched the requirements of cloud-native systems.

Maven

Şu satırı dahil ederiz

<dependency>
    <groupId>io.nats</groupId>
    <artifactId>java-nats</artifactId>
    <version>latest_version</version>
</dependency>

Docker

Şöyle yaparız

docker run -d -p 4222:4222 -p 8222:8222 --name nats-main nats:latest

Go to http://localhost:8222

Connection Sınıfı

constructor

application.properties şöyle olsun

nats.url=nats://localhost:4222

Şöyle yaparız

@Configuration
public class NatsConfig {
    
  @Value("${nats.url}")
  private String natsUrl;

  @Bean
  public Connection natsConnection() throws IOException, InterruptedException {
    Options options = new Options.Builder().server(natsUrl).build();
    return Nats.connect(options);
  }
}

publish metodu

Şöyle yaparız

@Autowired
private Connection natsConnection;

public void sendMessage(String subject, String message) {
  natsConnection.publish(subject, message.getBytes(StandardCharsets.UTF_8));
}

subscribe metodu

Şöyle yaparız

@Autowired
private Connection natsConnection;

public void subscribeToSubject(String subject) {
  natsConnection.subscribe(subject, msg -> {
    String receivedMessage = new String(msg.getData(), StandardCharsets.UTF_8);
    // Handle and process the received message
  });
}

SpringWebFlux Flux NettyServerCustomizer Arayüzü

Giriş
Şu satırı dahil ederiz 

import org.springframework.boot.web.embedded.netty.NettyServerCustomizer;

idleTimeout metodu

Açıklaması şöyle. Eğer bu değer verilmezse bağlantı hiç kapanmayabilir.

Reactor-Netty doesn’t have a default idle connection timeout.

Örnek

Şöyle yaparız

@Configuration
public class NettyServerCustomizerConfig {

  @Bean
  public NettyServerCustomizer nettyServerCustomizer() {
    return httpServer -> httpServer.idleTimeout(Duration.ofMillis(1));
  }
}

aynı şeyi şöyle yaparız

server:
  netty:
    idle-timeout: 1000 # 1 second of idle-timeout