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May 24, 2022

Scalable classes using Spring @Component and @Autowired

In this article, we will show you how to write a scalable abstract class using Spring @Component and @Autowired.

Overview

1. Abstract PaymentProcessor using @Component
2. Country-specific Payment Processors using @Component
3. Use @Autowired HashMap to store and retrieve country-specific PaymentProcessors
4. Payment RestController

Abstract PaymentProcessor using @Component

@Component
public abstract class PaymentProcessor {

    public Payment process(PaymentMessage message) {
        Payment payment = new Payment();
        payment.setCurrency(message.getCurrency());
        payment.setAmount(message.getAmount());
        payment.setUsdAmount(getUsdAmount(message.getAmount()));
        return payment;
    }

    public abstract BigDecimal getUsdAmount(BigDecimal amount);

}

Country-specific PaymentProcessors using @Component

/* SgpPaymentProcessor.java */
@Component("sgpPaymentProcessor")
public class SgpPaymentProcessor extends PaymentProcessor {

    private static final BigDecimal USD_CONVERSION_RATE = '1.4';

    @Override
    public BigDecimal getUsdAmount(BigDecimal amount) {
        return amount * USD_CONVERSION_RATE;
    }
}

/* MyPaymentProcessor.java */
@Component("myPaymentProcessor")
public class MyPaymentProcessor extends PaymentProcessor {

    private static final BigDecimal USD_CONVERSION_RATE = '4.39';

    @Override
    public BigDecimal getUsdAmount(BigDecimal amount) {
        return amount * USD_CONVERSION_RATE;
    }
}

Use @Autowired HashMap to store and retrieve country-specific PaymentProcessors

/* ProcessPaymentAction.java */
@Component
public class ProcessPaymentAction {

    private static final String PAYMENT_PROCESSOR = 'PaymentProcessor';

    @Autowired
    HashMap<String, PaymentProcessor> paymentProcessorMap;

    @Autowired
    PaymentServiceImpl paymentService;

    public boolean execute(PaymentMessage paymentMessage) {
        // Get country-specific payment processor from hashmap
        String country = paymentMessage.getCountry().toLowerCase();
        PaymentProcessor paymentProcessor = paymentProcessorMap.get(country + PAYMENT_PROCESSOR);

        // Process payment
        Payment payment = paymentProcessor.process(paymentMessage);

        // Save payment
        paymentService.save(payment);

        return true;
    }

}

Payment RestController

@RestController
public class PaymentController {

    @Autowired
    ProcessPaymentAction processPaymentAction;

    @PostMapping("/payment")
    boolean postPayment(@RequestBody PaymentMessage paymentMessage) {
        log.info("Request to initiate payment: {}", paymentMessage);
        boolean result = processPaymentAction.execute(paymentMessage);
        return result;
    }

}