Java producer client in Kafka - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Kafka producer with the correct property for the bootstrap servers.

Kafka

Properties props = new Properties();
props.put("bootstrap.servers", [1]);

Drag options to blanks, or click blank then click option'

A"localhost"

B"9092"

C"localhost:9092"

D"kafka:9092"

Attempts:

3 left

💡 Hint

Common Mistakes

Using only the host name without port.

Using only the port number.

Using an incorrect format without colon.

The bootstrap.servers property requires the host and port, like "localhost:9092".

2fill in blank

medium

Complete the code to set the key serializer class for the Kafka producer.

Kafka

props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, [1]);

Drag options to blanks, or click blank then click option'

A"org.apache.kafka.common.serialization.StringSerializer"

B"org.apache.kafka.common.serialization.IntegerSerializer"

C"org.apache.kafka.common.serialization.StringDeserializer"

D"org.apache.kafka.common.serialization.ByteArraySerializer"

Attempts:

3 left

💡 Hint

Common Mistakes

Using deserializer instead of serializer.

Using serializer for wrong data type.

The producer needs a serializer, so use StringSerializer for keys of type String.

3fill in blank

hard

Fix the error in the code to send a message to the Kafka topic.

Kafka

ProducerRecord<String, String> record = new ProducerRecord<>("my-topic", [1]);
producer.send(record);

Drag options to blanks, or click blank then click option'

A12345

Bnew String()

Cnull

D"Hello Kafka"

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an integer instead of a string.

Passing null which causes NullPointerException.

The message value must be a String, so "Hello Kafka" is correct.

4fill in blank

hard

Fill both blanks to create a Kafka producer and send a message with a key.

Kafka

Properties props = new Properties();
props.put("bootstrap.servers", [1]);
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, [2]);
KafkaProducer<String, String> producer = new KafkaProducer<>(props);

Drag options to blanks, or click blank then click option'

A"localhost:9092"

B"org.apache.kafka.common.serialization.StringDeserializer"

C"org.apache.kafka.common.serialization.StringSerializer"

D"localhost"

Attempts:

3 left

💡 Hint

Common Mistakes

Using deserializer instead of serializer.

Using incomplete bootstrap server address.

Use "localhost:9092" for bootstrap.servers and StringSerializer for key serializer.

5fill in blank

hard

Fill all three blanks to create a producer, send a keyed message, and close the producer.

Kafka

Properties props = new Properties();
props.put("bootstrap.servers", [1]);
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, [2]);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, [3]);
KafkaProducer<String, String> producer = new KafkaProducer<>(props);
ProducerRecord<String, String> record = new ProducerRecord<>("my-topic", "key1", "value1");
producer.send(record);
producer.close();

Drag options to blanks, or click blank then click option'

A"localhost:9092"

B"org.apache.kafka.common.serialization.StringSerializer"

D"org.apache.kafka.common.serialization.StringDeserializer"

Attempts:

3 left

💡 Hint

Common Mistakes

Using deserializer instead of serializer for producer.

Forgetting to close the producer.

Use "localhost:9092" for bootstrap.servers and StringSerializer for both key and value serializers.

Practice

1. What is the primary role of a Java producer client in Kafka?

easy

A. To send messages to Kafka topics

B. To consume messages from Kafka topics

C. To manage Kafka brokers

D. To monitor Kafka cluster health

Solution

1. Step 1: Understand Kafka client roles

   Kafka has producers that send messages and consumers that receive messages.

2. Step 2: Identify the producer's function

   A Java producer client specifically sends messages to Kafka topics.

3. Final Answer:

   To send messages to Kafka topics -> Option A

4. Quick Check:

   Producer = send messages [OK]

Hint: Producer sends, consumer receives messages [OK]

Common Mistakes:

• Confusing producer with consumer
• Thinking producer manages brokers
• Assuming producer monitors cluster

2. Which of the following is the correct way to set the serializer for the key in a Java Kafka producer?

easy

A. props.add("key.serializer", "StringSerializer");

B. props.set("key.serializer", "StringSerializer");

C. props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");

D. props.put("key.serializer", String.class);

Solution

1. Step 1: Recall how to set properties in Kafka producer

   Kafka producer uses Properties object with put(key, value) method.

2. Step 2: Identify correct serializer setting syntax

   The key.serializer must be set to the full class name as a string.

3. Final Answer:

   props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer"); -> Option C

4. Quick Check:

   Use props.put with full serializer class name [OK]

Hint: Use props.put with full serializer class name string [OK]

Common Mistakes:

• Using props.set or props.add instead of put
• Not using full class name string
• Passing class type instead of string

3. What will be the output of the following Java Kafka producer code snippet?

import java.util.Properties;
import org.apache.kafka.clients.producer.*;
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

Producer<String, String> producer = new KafkaProducer<>(props);
ProducerRecord<String, String> record = new ProducerRecord<>("my-topic", "key1", "value1");
producer.send(record);
producer.close();
System.out.println("Message sent");

medium

A. Message sent

B. Compilation error due to missing imports

C. Runtime error due to missing Kafka server

D. No output

Solution

1. Step 1: Analyze the code flow

   The code creates a producer, sends a message, closes the producer, then prints "Message sent".

2. Step 2: Consider output behavior

   Assuming Kafka server is running and imports are correct, the print statement executes after send and close.

3. Final Answer:

   Message sent -> Option A

4. Quick Check:

   Print after send and close = "Message sent" [OK]

Hint: Print statement runs after send, shows "Message sent" [OK]

Common Mistakes:

• Assuming send() blocks until message delivered
• Ignoring that print runs regardless of Kafka server
• Confusing compile errors with runtime issues

4. Identify the error in this Java Kafka producer code snippet:

import java.util.Properties;
import org.apache.kafka.clients.producer.*;
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

KafkaProducer<String, String> producer = new KafkaProducer<>(props);
ProducerRecord<String, String> record = new ProducerRecord<>("my-topic");
producer.send(record);
producer.close();

medium

A. Producer not closed properly

B. Incorrect serializer class name

C. Missing bootstrap.servers property

D. ProducerRecord missing key argument

Solution

1. Step 1: Check ProducerRecord constructor usage

   The constructor used has only topic, but the generic type expects key and value.

2. Step 2: Identify mismatch in arguments

   ProducerRecord<String, String> expects key and value, but no key/value is provided, causing a compile error.

3. Final Answer:

   ProducerRecord missing key argument -> Option D

4. Quick Check:

   ProducerRecord requires key and value [OK]

Hint: ProducerRecord needs key and value if generics specify both [OK]

Common Mistakes:

• Using wrong ProducerRecord constructor
• Ignoring generic type mismatch
• Assuming value-only constructor works with key type

5. You want to send multiple messages to different Kafka topics using a single Java producer instance efficiently. Which approach is best?

hard

A. Create a new KafkaProducer for each message

B. Reuse one KafkaProducer and send ProducerRecords with different topics

C. Use multiple threads each with its own KafkaProducer

D. Send all messages to one topic and then move them to others

Solution

1. Step 1: Understand KafkaProducer resource usage

   Creating a producer is expensive; reusing one instance is efficient.

2. Step 2: Sending to multiple topics

   ProducerRecords can specify different topics; one producer can send to many topics.

3. Step 3: Evaluate other options

   Creating many producers wastes resources; sending all to one topic is incorrect.

4. Final Answer:

   Reuse one KafkaProducer and send ProducerRecords with different topics -> Option B

5. Quick Check:

   One producer, multiple topics via records [OK]

Hint: Reuse one producer; specify topic per ProducerRecord [OK]

Common Mistakes:

• Creating many producers wastes resources
• Sending all messages to one topic incorrectly
• Assuming each thread needs its own producer