> 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 %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.digit.org/platform/guides/developer-guide/backend-developer-guide/section-1-create-project/implement-service-layer.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.