Sample Spring Boot application

• Application overview
• How to start the application
• How to test the application
• How to build and push the docker image

Application overview

This sample spring boot application uses Kafka APIs to send/receive JSON messages to/from IBM Event Streams (Kafka) topic. It saves the JSON message in IBM Databases for MongoDB.

How to start the application

1. Set the following environment variables to connect to IBM Databases for MongoDB.

export MONGO_DB_URL=<database_url starting with mongodb://>
export MONGO_DB_NAME=<database_name>

2. Download the certificate from IBM Databases for MongoDB instance dashboard, generate the JKS or use JDK cacerts and import the MongoDB certificate in JKS.

keytool -genkey -alias <fully_qualified_domain_name> -keyalg RSA -keystore <key_store_name>.jks -keysize 2048
or
cp <JDK_Cert_Path>/cacerts <key_store_name>.jks     # Use the existing JDK cacerts as JKS.
keytool -storepasswd -keystore keystore.jks     # change the JKS password.
keytool -importcert -trustcacerts -file <certificate_file_full_path> -keystore <key_store_name>.jks -storepass <key_store_password> \
-alias <certificate_specific_unique_name>

3. From the Event Streams for IBM Cloud instance dashboard, click Service Credentials and select or create a new one.

4. Copy the above created credentials content to the environment variable ES_KAFKA_SERVICE to connect to IBM Event Streams (Kafka). Set environment variable ES_KAFKA_TOPIC_NAME.

export ES_KAFKA_SERVICE='{
  "api_key": "...",
  "apikey": "...",
  "iam_apikey_description": "...",
  "iam_apikey_name": "...",
  "iam_role_crn": "...",
  "iam_serviceid_crn": "...",
  "instance_id": "...",
  "kafka_admin_url": "...",
  "kafka_brokers_sasl": [
    "...",
    "...",
  ],
  "kafka_http_url": "...",
  "password": "...",
  "user": "..."
}'

export ES_KAFKA_TOPIC_NAME=es-kafka-sample-topic

5. Install event-stream cli and initialize it to connect to event stream instance.

ibmcloud plugin install event-streams
ibmcloud es init

6. Build .jar file and start the application by passing JVM parameters as in below.

mvn clean install
java -Djavax.net.ssl.trustStore=<key_store_full_path>.jks -Djavax.net.ssl.trustStorePassword=<key_store_password> \
-jar <generated_jar_file_full_path>.jar

How to test the application

The application saves and retrieves employee data and can be accessed through the endpoint localhost:8080/employee.

1. Send a POST request with following JSON to save employee data. The POST request sends the data to Kafka topic. Kafka consumer listens to the message and save it into MongoDB.

{
	"name": "..",
	"address": "...",
	"deptName": "..."
}

2. Send a GET request to retrieve all the employees.

How to build and push the docker image

docker -t <registry_url>/<repo_name>/<image_name>:<image_version> build .
docker push <registry_url>/<repo_name>/<image_name>:<image_version>