Price provider

By default, the @X402PayUSDC annotation uses a fixed price, defined directly in the amount field:

@X402PayUSDC(amount = "5.00")
@GetMapping("/data")
public ResponseEntity<String> getData() {
    return ResponseEntity.ok("Here is your protected data");
}

In some cases, however, the required payment amount depends on runtime conditions. For example, query parameters, user tiers, or data size. To handle this, you can use a dynamic pricing provider via the amountProvider field.

🧩 Step 1 — Implement an AmountProvider.

An AmountProvider is a simple Java interface:

public interface AmountProvider {
    BigDecimal getAmount(HttpServletRequest request);
}

It receives the current HTTP request and returns the amount.

Example : Simple fixed provider

public final class SimpleAmountProvider implements AmountProvider {
    @Override
    public BigDecimal getAmount(HttpServletRequest request) {
        return new BigDecimal("0.10"); // always 10 cents
    }
}

Example : Provider based on query parameters

public final class TypeBasedProvider implements AmountProvider {
    @Override
    public BigDecimal getAmount(HttpServletRequest request) {
        String type = request.getParameter("type");
        return switch (type) {
            case "image" -> new BigDecimal("0.20");
            case "text" -> new BigDecimal("0.05");
            default -> new BigDecimal("0.01");
        };
    }
}

🧩 Step 2 — Reference your provider in the annotation

Simply reference the class in the annotation:

@X402PayUSDC(amount = "5.00", amountProvider = TypeBasedProvider.class)
@GetMapping("/generate")
public ResponseEntity<String> generate() {
    return ResponseEntity.ok("Generated content");
}

At runtime, Mogami’s resolver automatically:

1. Checks if the provider class is a Spring Bean (@Component, @Service, etc.).

2. Falls back to manual instantiation if it’s a plain Java class.

3. The amount field is ignored if amountProvider is set