I'll help implement this feature in Spring Boot. We'll create a service that checks for retry attempts and handles non-billing transactions appropriately. package com.example.billing.service; import com.example.billing.model.Transaction; import com.example.billing.model.TransactionStatus; import com.example.billing.model.BillingSchedule; import com.example.billing.repository.TransactionRepository; import org.springframework.stereotype.Service; import java.util.List; @Service public class TransactionService { private final TransactionRepository transactionRepository; public TransactionService(TransactionRepository transactionRepository) { this.transactionRepository = transactionRepository; } public BillingSchedule processTransaction(Transaction transaction) { // Check for retry List existingTransactions = transactionRepository .findByReferenceId(transaction.getReferenceId()); if (!existingTransactions.isEmpty()) { // Transaction already processed, return existing schedule return existingTransactions.get(0).getBillingSchedule(); } // Check for non-billing transaction types if (isNonBillingTransaction(transaction)) { throw new IllegalArgumentException( "Transaction type " + transaction.getType() + " is not eligible for billing"); } // Process new transaction transaction.setStatus(TransactionStatus.PROCESSING); Transaction savedTransaction = transactionRepository.save(transaction); // Generate billing schedule (implementation depends on your business logic) BillingSchedule schedule = generateBillingSchedule(transaction); savedTransaction.setBillingSchedule(schedule); savedTransaction.setStatus(TransactionStatus.COMPLETED); transactionRepository.save(savedTransaction); return schedule; } private boolean isNonBillingTransaction(Transaction transaction) { String type = transaction.getType(); return "REND".equals(type) || "REX".equals(type) || "NRR".equals(type); } private BillingSchedule generateBillingSchedule(Transaction transaction) { // Implement your billing schedule generation logic here return new BillingSchedule(); // placeholder } } package com.example.billing.model; import jakarta.persistence.*; import lombok.Data; @Entity @Data public class Transaction { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String referenceId; private String type; @Enumerated(EnumType.STRING) private TransactionStatus status; @OneToOne(cascade = CascadeType.ALL) private BillingSchedule billingSchedule; // other fields as needed } package com.example.billing.model; public enum TransactionStatus { NEW, PROCESSING, COMPLETED, FAILED } package com.example.billing.model; import jakarta.persistence.*; import lombok.Data; @Entity @Data public class BillingSchedule { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; // Add your billing schedule fields here // For example: startDate, endDate, frequency, etc. } package com.example.billing.repository; import com.example.billing.model.Transaction; import org.springframework.data.jpa.repository.JpaRepository; import java.util.List; public interface TransactionRepository extends JpaRepository { List findByReferenceId(String referenceId); } package com.example.billing.controller; import com.example.billing.model.Transaction; import com.example.billing.model.BillingSchedule; import com.example.billing.service.TransactionService; import org.springframework.web.bind.annotation.*; @RestController @RequestMapping("/api/transactions") public class TransactionController { private final TransactionService transactionService; public TransactionController(TransactionService transactionService) { this.transactionService = transactionService; } @PostMapping public BillingSchedule processTransaction(@RequestBody Transaction transaction) { return transactionService.processTransaction(transaction); } }