> For the complete documentation index, see [llms.txt](https://docs.digit.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.digit.org/platform/guides/developer-guide/backend-developer-guide/section-1-create-project/implement-service-layer.md).

# Implement Service Layer

## **Overview**

The service layer performs business logic on the RequestData and prepares the Response to be returned back to the client.

## **Steps**

Follow the steps below to create the service layer.

1. Create a new package called Service.
2. Create a new class in this folder by the name BirthRegistrationService.
3. Annotate the class with @Service annotation.
4. Add the following content to the class -

   ```java
   package digit.service;


   import digit.enrichment.BirthApplicationEnrichment;
   import digit.kafka.Producer;
   import digit.repository.BirthRegistrationRepository;
   import digit.validators.BirthApplicationValidator;
   import digit.web.models.BirthApplicationSearchCriteria;
   import digit.web.models.BirthRegistrationApplication;
   import digit.web.models.BirthRegistrationRequest;
   import lombok.extern.slf4j.Slf4j;
   import org.egov.common.contract.request.RequestInfo;
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.stereotype.Service;
   import org.springframework.util.CollectionUtils;

   import java.util.ArrayList;
   import java.util.Collections;
   import java.util.List;

   @Service
   @Slf4j
   public class BirthRegistrationService {

       @Autowired
       private BirthApplicationValidator validator;

       @Autowired
       private BirthApplicationEnrichment enrichmentUtil;

       @Autowired
       private UserService userService;

       @Autowired
       private WorkflowService workflowService;

       @Autowired
       private BirthRegistrationRepository birthRegistrationRepository;

       @Autowired
       private Producer producer;

       public List<BirthRegistrationApplication> registerBtRequest(BirthRegistrationRequest birthRegistrationRequest) {
           // Validate applications
           validator.validateBirthApplication(birthRegistrationRequest);

           // Enrich applications
           enrichmentUtil.enrichBirthApplication(birthRegistrationRequest);

   //         Enrich/Upsert user in upon birth registration
           userService.callUserService(birthRegistrationRequest);
   //
           // Initiate workflow for the new application
           workflowService.updateWorkflowStatus(birthRegistrationRequest);

           // Push the application to the topic for persister to listen and persist
           producer.push("save-bt-application", birthRegistrationRequest);

           // Return the response back to user
           return birthRegistrationRequest.getBirthRegistrationApplications();
       }

       public List<BirthRegistrationApplication> searchBtApplications(RequestInfo requestInfo, BirthApplicationSearchCriteria birthApplicationSearchCriteria) {
           // Fetch applications from database according to the given search criteria
           List<BirthRegistrationApplication> applications = birthRegistrationRepository.getApplications(birthApplicationSearchCriteria);

           // If no applications are found matching the given criteria, return an empty list
           if(CollectionUtils.isEmpty(applications))
               return new ArrayList<>();

           // Enrich mother and father of applicant objects
           applications.forEach(application -> {
               enrichmentUtil.enrichFatherApplicantOnSearch(application);
               enrichmentUtil.enrichMotherApplicantOnSearch(application);
           });

           // Otherwise return the found applications
           return applications;
       }

       public BirthRegistrationApplication updateBtApplication(BirthRegistrationRequest birthRegistrationRequest) {
           // Validate whether the application that is being requested for update indeed exists
           BirthRegistrationApplication existingApplication = validator.validateApplicationExistence(birthRegistrationRequest.getBirthRegistrationApplications().get(0));
           existingApplication.setWorkflow(birthRegistrationRequest.getBirthRegistrationApplications().get(0).getWorkflow());
           log.info(existingApplication.toString());
           birthRegistrationRequest.setBirthRegistrationApplications(Collections.singletonList(existingApplication));

           // Enrich application upon update
           enrichmentUtil.enrichBirthApplicationUponUpdate(birthRegistrationRequest);

           workflowService.updateWorkflowStatus(birthRegistrationRequest);

           // Just like create request, update request will be handled asynchronously by the persister
           producer.push("update-bt-application", birthRegistrationRequest);

           return birthRegistrationRequest.getBirthRegistrationApplications().get(0);
       }
   }
   ```

```java
```

{% hint style="info" %}
**NOTE:** At this point, your IDE must be showing a lot of errors but do not worry we will add all dependent layers as we progress through this guide and the errors will go away.
{% endhint %}


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