How to call a function of one CAP Java application from a different CAP Java application locally?

[#1]

I have created a two SAP CAP Java App. Now i want to call a function of 2nd CAP Java application from  the 1st CAP Java application locally to check whether the Correlation IDs are same or not.
Currently I am using RestTemplate to call the function but i have to manually pass the Correlation Id in the header otherwise the Correlation Ids are not same.

1st App (running on port 8080):

package customer.bookstore.handlers;

import java.util.Collections;
import java.util.UUID;

import org.apache.commons.codec.binary.Base64;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;

import com.sap.cds.Result;
import com.sap.cds.ql.Select;
import com.sap.cds.ql.cqn.CqnSelect;
import com.sap.cds.services.handler.EventHandler;
import com.sap.cds.services.handler.annotations.On;
import com.sap.cds.services.handler.annotations.ServiceName;
import com.sap.cds.services.persistence.PersistenceService;
import com.sap.hcp.cf.logging.common.LogContext;

import cds.gen.booksservice.Authors;
import cds.gen.booksservice.Authors_;
import cds.gen.booksservice.GetAuthorContext;

@Component
@ServiceName("BooksService")
public class BooksService implements EventHandler {

    private Logger LOG = LoggerFactory.getLogger(BooksService.class);
    private static final String CORRELATION_ID_HEADER_NAME = "X-CorrelationID";
    
    @Autowired
    PersistenceService db;

    @Autowired
    OrdersService ordersService;

    @Autowired
    RestTemplate restTemplate;

    (event = GetAuthorContext.CDS_NAME)
    private void getAuthor(GetAuthorContext context) {
        LOG.info("***Inside getAuthor()***");

        String correlationId = LogContext.getCorrelationId();
        LOG.info("***Correlation ID***: {}", correlationId);
        if (correlationId == null) {
            correlationId = UUID.randomUUID().toString();
        }
        LOG.info("Using Correlation ID: {}", correlationId);

        CqnSelect selectDynamic = Select.from(Authors_.class).columns("firstname")
                .byId("286ae4b1-b845-4af8-9827-4eb04fe5f380");

        Result getAuthorResult = db.run(selectDynamic);
        LOG.info("***getBookResult***: {}", getAuthorResult);

        Authors author = getAuthorResult.single(Authors.class);
        LOG.info("***book-info***: {}", author);
        LOG.error("***book-error***: {}", author);
        LOG.debug("***book-debug***: {}", author);

        String plainCreds = "authenticated:";
        byte[] plainCredsBytes = plainCreds.getBytes();
        byte[] base64CredsBytes = Base64.encodeBase64(plainCredsBytes);
        String base64Creds = new String(base64CredsBytes);

        HttpHeaders headers = new HttpHeaders();
        headers.add("Authorization", "Basic " + base64Creds);
        headers.add(CORRELATION_ID_HEADER_NAME, correlationId);
        headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));

        // // Call the external CAP Java app using RestTemplate
        String url = "http://localhost:8081/odata/v4/BookService/getBook()";
        HttpEntity<String> request = new HttpEntity<>(headers);

        try {   
            ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.GET, request, String.class);
            if (response.getStatusCode().is2xxSuccessful()) {
                LOG.info("***External API Response - author***: {}", response.getBody());
            } else {
                LOG.error("***Failed to call external API*** Status: {}", response.getStatusCode());
            }
        } catch (Exception e) {
            LOG.error("***Error calling external API***: {}", e);
        }

        context.setResult(author);
    }

}

2nd App (running on port 8081):

package customer.books.handlers;

import java.util.UUID;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.sap.cds.Result;
import com.sap.cds.ql.Select;
import com.sap.cds.ql.cqn.CqnSelect;
import com.sap.cds.services.handler.EventHandler;
import com.sap.cds.services.handler.annotations.On;
import com.sap.cds.services.handler.annotations.ServiceName;
import com.sap.cds.services.persistence.PersistenceService;
import com.sap.cds.services.request.ParameterInfo;
import com.sap.hcp.cf.logging.common.LogContext;

import cds.gen.bookservice.Books;
import cds.gen.bookservice.Books_;
import cds.gen.bookservice.GetBookContext;

@Component
@ServiceName("BookService")
public class BookServiceHandler implements EventHandler {
    
    private Logger LOG = LoggerFactory.getLogger(BookServiceHandler.class);

    @Autowired
    PersistenceService db;

    @Autowired
    ParameterInfo parameterInfo;

    (event = GetBookContext.CDS_NAME)
    private void getBook(GetBookContext context){
        ParameterInfo parameterInfo = context.getParameterInfo();
        LOG.info("***REST - Inside getBook()*** : {}", parameterInfo.getHeaders());
        
        CqnSelect selectDynamic = Select.from(Books_.class).columns("name").byId(1);
        
        Result getBookResult = db.run(selectDynamic);
        LOG.info("***REST - getBookResult***: {}", getBookResult);

        Books book = getBookResult.single(Books.class);
        LOG.info("***REST - book-info***: {}", book);
        LOG.error("***REST - book-error***: {}", book);
        LOG.debug("***REST - book-debug***: {}", book);

        context.setResult(book);
    }

}

  I don't want to use Rest Template instead i want to use the SAP CAP suggested Remote Services
to basically test whether the Correlation Ids are same or not.
Reference: https://cap.cloud.sap/docs/java/operating-applications/observability#correlation-ids 

Please guide me to achieve it? 
It would be of great help.

Thanks,
Abhinav.