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Tips for optimizing your stack operations.

Optimizing Stack Operations: Tips for Efficient and Secure Management

If you're brand new to Kafka, be sure to check out this <a id=0 href='https://www.stackchief.com/blog/Kafka%20Architecture%20Explained'>intro to Kafka architecture</a> first.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-parent</artifactId>

<description>Demo project for Spring Boot</description>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter</artifactId>

<groupId>org.springframework.kafka</groupId>

<groupId>com.fasterxml.jackson.core</groupId>

<artifactId>jackson-databind</artifactId>

<artifactId>spring-boot-starter-test</artifactId>

<artifactId>spring-kafka-test</artifactId>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-maven-plugin</artifactId>

The pom.xml defines the dependencies we need for our Maven build. Notice how we include the dependencies needed for Spring Boot along with those needed for running and testing Kafka.

Note that the jackson-databind dependency is included to account for bugs in older versions of the Spring Kafka library. You may not need to include this depending on which version of Kafka you're using..

	public static void main(String[] args) {

		SpringApplication.run(DemoApplication.class, args);

The DemoApplication.java class runs our Spring Boot application.

Spring Boot automatically configures Kafka via @SpringBootApplication. With this annotation, Spring provides/configures a KafkaAutoConfiguration class for you.

import org.springframework.kafka.annotation.KafkaListener;

import org.springframework.stereotype.Component;

    public void processMessage(String content){

        System.out.println("Message received: " + content);

The Consumer.java class is what actually listens for messages. Notice how we specify the topics to listen to within the @KafkaListener annotation.

By simply using the annotations provided by the Spring Boot Kafka library, we are able to easily set up a consumer for a given topic.

spring.kafka.bootstrap-servers=localhost:9092

Thanks to auto-configuration, you only need to define a few things in application.properties to configure the consumer. Notice how our app is configured to use Kafka locally.

This example is configured to consume from a local Kafka topic.  You'll need to have Kafka installed and running locally to see messages being consumed from the Spring Boot app.

To start Kafka locally, you need to start both the Zookeeper and Kafka servers locally...

./zookeeper-server-start /usr/local/etc/kafka/zookeeper.properties

This will start the zookeeper server with the default configurations.  Please note the path to your local Kafka install may vary.

./kafka-server-start /usr/local/etc/kafka/server.properties 

This will start the Kafka server with the default configurations.  Please note the path to your local Kafka install may vary.

To test the application consumer, you'll need to produce some messages for the test topic.  To start a Kafka console producer:

./kafka-console-producer --bootstrap-server=localhost:9092 --topic test

This starts a Kafka producer for the test topic. Notice how both the bootstrap-server and topic arguments match what we've defined in our application.properties file.

Once the producer is up and running, you can send a message to the test topic like this:

If everything is working correctly, you should see the message being logged through the Spring application like this:

Spring Boot Kafka Consumer example including consumer offsets and multiple consumer examples.

Spring Boot Kafka Consumer

An introduction to parsing command line arguments with the getopts command including parameters, multiple arguments, and error handling with examples.

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What is identity and access management?

How does OAuth work in REST API?

Why is Kafka important?

What is difference between event driven and REST API?

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Before jumping into @OneToOne examples, be sure to understand the basics of <a id=0 href='https://www.stackchief.com/blog/Spring%20Data%20JPA'>Spring Data JPA</a>.

1) @OneToOne Example Using Shared Primary Key (Best Approach)

    @GeneratedValue(strategy = GenerationType.AUTO)

    @OneToOne(mappedBy = "author", cascade = CascadeType.ALL)

This creates a one-to-one relationship between an author and book table. A book has one author and an author has one book.

Using the @OneToOne annotation, Hibernate knows to create a one-to-one relationship between the two entities.

The mappedBy="author" option tells Hibernate that the owning side of the relationship is the book table. This means the book table will hold the foreign key reference to the author table.

The cascade = CascadeType.ALL tells Hibernate to propagate changes to all associated entities. If you delete an instance of Author it will delete the associated Book entity automatically.

The @PrimaryKeyJoinColumn tells Hibernate that the primary key for the author table will be used as the foreign key in the owning book table.

The @MapsId tells Hibernate that the primary key on the author table will be used as the primary key for the book table. Since the primary key is being reused, we don't need a to specify @GenderatedValue on the book table.

This generates the following in the database...

When retrieving entities from the database, associations will be eagerly loaded by default:

Author author = authorRepo.findById(24) //returns both the author and its associated book in single DB call

By utilizing the primary key of the author as both the primary key and foreign key of the book table, you achieve the same result with fewer keys. This saves operating costs as primary/foreign keys are typically indexed and loaded into memory for efficient lookups. You're achieving the same result with fewer keys via a unidirectional relationship.

With this approach, the author table is the owning side of the relationship. This means the author table will have the foreign key book_id. For these reasons, the mappedBy = is moved to the Book entity definition.

Since the primary key is no longer being reused in both tables, the Book entity must now generate its own id values. For these reasons, the @GeneratedValue annotation exists on both entity classes.

Note: Unlike the last example, we now save the author entity to create the associations in the database. Whichever side owns the relationship must be saved to create entries in both tables.. Otherwise, you will run into issues with transient objects not being saved and exceptions being thrown.

Notice how the author table now has 2 columns.  This is because a foreign key is being used to create a bidirectional relationship between books and authors.

This example clearly demonstrates the advantage of the first approach as an extra book_id is needed to achieve the relationship.

                    { @JoinColumn(name = "author_id", referencedColumnName = "id") },

                    { @JoinColumn(name = "book_id", referencedColumnName = "id") })

One to One Example using Spring Data JPA and Hibernate including shared primary key, unidirectional, and bidirectional examples.

One To One Example | Spring Data JPA

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blazingSaddles

What is an algorithm?

Optimizing Stack Operations: Tips for Efficient and Secure Management

Spring Boot Kafka Consumer

Spring Boot Kafka Consumer

Bash Tutorial: getopts

What is identity and access management?

How does OAuth work in REST API?

Why is Kafka important?

What is difference between event driven and REST API?

What is a microservice?

One To One Example | Spring Data JPA

How much do software engineers make?

Is Java 17 worth it?

How to Implement User Authentication in Java Web Apps

What are KafkaListener Annotation Properties?

KafkaMessageListenerContainer vs ConcurrentMessageListenerContainer?

What is Kafka consumer poll?

Does anyone have issues with JSON Serializer in Kafka?

blazingSaddles

What is an algorithm?

Optimizing Stack Operations: Tips for Efficient and Secure Management

Spring Boot Kafka Consumer

Spring Boot Kafka Consumer

Bash Tutorial: getopts

What is identity and access management?

How does OAuth work in REST API?

Why is Kafka important?

What is difference between event driven and REST API?

What is a microservice?

One To One Example | Spring Data JPA

How much do software engineers make?

Is Java 17 worth it?

How to Implement User Authentication in Java Web Apps

What are KafkaListener Annotation Properties?

KafkaMessageListenerContainer vs ConcurrentMessageListenerContainer?

What is Kafka consumer poll?

Does anyone have issues with JSON Serializer in Kafka?

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