MongoTemplate null pointer exception in class - spring

Question

I have been looking at other answers but none of the seem to work for me, I have a spring boot application where I am using mongo and kafka. In the main class where my run() method is I am able to #Autowired mongoTemplate and it works but then in another class I did the same and I am getting a null pointer exception on the mongoTemplate.
Here are both classes:
Working
#SpringBootApplication
public class ProducerConsumerApplication implements CommandLineRunner {
public static Logger logger = LoggerFactory.getLogger(ProducerConsumerApplication.class);
public static void main(String[] args) {
SpringApplication.run(ProducerConsumerApplication.class, args).close();
}
#Autowired
private Sender sender;
#Autowired
MongoTemplate mongoTemplate;
#Override
public void run(String... strings) throws Exception {
Message msg = new Message();
msg.setCurrentNode("my_node");
msg.setStartTime(System.currentTimeMillis());
String json = "{ \"color\" : \"Orange\", \"type\" : \"BMW\" }";
ObjectMapper objectMapper = new ObjectMapper();
msg.setTest(objectMapper.readValue(json, new TypeReference<Map<String,Object>>(){}));
sender.send(msg);
mongoTemplate.createCollection("test123");
mongoTemplate.dropCollection("test123");
}
Not working
#Component
public class ParentNode extends Node{
#Autowired
public MongoTemplate mongoTemplate;
public void execute(Message message) {
try{
// GET WORKFLOWS COLLECTION
MongoCollection<Document> collection = mongoTemplate.getCollection("workflows");
} catch(Exception e){
e.printStackTrace();
}
}
}
Thank you for the help. It is much appreciated.

Answer 1

can you try to inject dependency with setter or constructor:
Method 1:
#Component
public class ParentNode extends Node{
#Autowired
public ParentNode(MongoTemplate mongoTemplate){
this.mongoTemplate = mongoTemplate;
}
private final MongoTemplate mongoTemplate;
public void execute(Message message) {
try{
// GET WORKFLOWS COLLECTION
MongoCollection<Document> collection = mongoTemplate.getCollection("workflows");
} catch(Exception e){
e.printStackTrace();
}
}
Method 2:
#Component
public class ParentNode extends Node{
#Autowired
public void setMongoTemplate(MongoTemplate mongoTemplate){
ParentNode.mongoTemplate = mongoTemplate;
}
static private MongoTemplate mongoTemplate;
public void execute(Message message) {
try{
// GET WORKFLOWS COLLECTION
MongoCollection<Document> collection = mongoTemplate.getCollection("workflows");
} catch(Exception e){
e.printStackTrace();
}
}