由于 spring 上下文的双重加载，SpringBoot 无法将 bean 注入 kafkaConumser 即在 spring 托管类之外的类中

Question

I am using spring boot starter 2.2.0.RELEASE for my application. I have one kafka consumer. Now I want to inject my spring entities into my kafka consumer (kafka consumer is not managed by spring container).

I tried ApplicationContextAware but it didn't helped me. I am getting applicationContext as null in my kafka consumer and hence I am not able to get bean from spring container. First time applicationContext is getting set properly but when context loads second time it set to null. Below are the details of my application in short

@SpringBootApplication
@ComponentScan({"com.xyz.config_assign.service"})
public class ConfigAssignServer {

    private static Logger log = LoggerFactory.getLogger(ConfigAssignServer.class);

    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(ConfigAssignServer.class, args);

        log.info("Started ConfigAssign Server!!! AppName= {} ", applicationContext.getApplicationName());

       QkafkaClient.loadConfiguration();


    }

}

All my application classes are present in com.xyz.config_assign.service so no issue of bean scanning problem. It worked well before I add Kafka consumer

My ApplicationContextProvider which is using famous ApplicationContextAware

@Component
public class ApplicationContextProvider implements ApplicationContextAware{

    public static ApplicationContext applicationContext;


    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        ApplicationContextProvider.applicationContext = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }
}

And now my kafkaconsumer

    public class ConfigAssignmentAssetTagChangeKafkaTopicProcessor implements BatchTopicProcessor<String, String> {

    private Logger log = LoggerFactory.getLogger(ConfigAssignmentAssetTagChangeKafkaTopicProcessor.class);


    private AssignConfigServiceImpl assignConfigServiceImpl;

    public  ConfigAssignmentAssetTagChangeKafkaTopicProcessor(){
        ApplicationContext applicationContext = ApplicationContextProvider.getApplicationContext();
        assignConfigServiceImpl = applicationContext.getBean(AssignConfigServiceImpl.class);
    }

    @Override
    public void handleError(ConsumerRecords<String, String> arg0, Exception arg1) {
        // TODO Auto-generated method stub

    }

    @Override
    public void process(ConsumerRecords<String, String> records, long arg1) {}
}

And the service I want to inject into kafka consumer is

   @Service
public class AssignConfigServiceImpl implements AssignConfigService {

    private Logger log = LoggerFactory.getLogger(AssignConfigServiceImpl.class);

    @Autowired
    private ConfigProfileDBService dbService;



    public boolean assignConfigToAgents(List<UUID> agentList, long customerId) {
        List<AgentConfigurationProfile> configProfiles = 
        dbService.getConfigurationProfilesForCustomer(customerId);
        boolean isAssignSuccessful = assignConfigToAgents(agentList, customerId, configProfiles);
        log.info("Config Assignment status ={}", isAssignSuccessful);

        return isAssignSuccessful;

    }

The other service I used is

@Service
public class ConfigProfileDBService implements DBService {

    private static Logger log = LoggerFactory.getLogger(ConfigProfileDBService.class);

    @Autowired
    private JdbcTemplate jdbcTemplate;


    public List<AgentConfigurationProfile> getConfigurationProfilesForCustomer(Long customerId) {
        List<AgentConfigurationProfile> agentConfigList;
}

}

Can someone please let me know what went wrong, I tried multiple online solution but didn't worked for me. Thanks in advance. Note : I haven't initialized any class using new operator.

Answer 1

Based on clarifications in question and comments, and assuming its impossible to move KafkaConsumer to be spring managed (which is I believe the best solution):

@Autowired won't work in KafkaConsumer, so no need to put that annotation.

I assume that you're getting null for Application context in this line:

 ApplicationContext applicationContext = ApplicationContextProvider.getApplicationContext();

This means that ApplicationContextProvider#setApplicationContext has not been called by the time you create Kafka Consumer. Spring in addition to injection also manages lifecyle of the managed objects. Since you're not in spring, you're "on-your-own" and you have to make sure that Application Context gets created first and only after that create other objects (like Kafka Consumer for example).

When application context starts it adds beans one by one at some point, among other beans it also gets to the ApplicationContextProvider and calls its setter.

Answer 2

My main problem was my spring context was being loaded twice. As I printed every class's class loader I found that my Application was running twice. (ie when I debug in intellij after pressing F9 I was again landing up on same line ie

ConfigurableApplicationContext applicationContext = SpringApplication.run(ConfigAssignServer.class, args);

My problem was in pom.xml. I removed below dependency from my pom and it worked.

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <scope>runtime</scope>
    </dependency>

Please check for your dependencies. Hope it will help someone. Enjoy coding :)