要使用DNS而不是IP地址来限制AWS API网关的IP流量，可以通过将IP地址转换为域名进行限制。下面是一个示例代码，使用Java编写：

import com.amazonaws.services.apigateway.AmazonApiGateway;
import com.amazonaws.services.apigateway.model.CreateUsagePlanRequest;
import com.amazonaws.services.apigateway.model.CreateUsagePlanResult;
import com.amazonaws.services.apigateway.model.GetUsagePlanRequest;
import com.amazonaws.services.apigateway.model.GetUsagePlanResult;
import com.amazonaws.services.apigateway.model.UpdateUsagePlanRequest;
import com.amazonaws.services.apigateway.model.UpdateUsagePlanResult;
import com.amazonaws.services.apigateway.model.UsagePlan;
import com.amazonaws.services.apigateway.model.UsagePlanKey;

public class Main {

    public static void main(String[] args) {
        String apiGatewayId = "your-api-gateway-id";
        String usagePlanName = "your-usage-plan-name";
        String domainName = "your.domain.name";

        // 创建Usage Plan
        CreateUsagePlanResult createUsagePlanResult = createUsagePlan(apiGatewayId, usagePlanName);
        String usagePlanId = createUsagePlanResult.getId();

        // 更新Usage Plan的API Stage
        updateUsagePlan(apiGatewayId, usagePlanId, domainName);
    }

    private static CreateUsagePlanResult createUsagePlan(String apiGatewayId, String usagePlanName) {
        AmazonApiGateway apiGatewayClient = AmazonApiGatewayClientBuilder.defaultClient();

        CreateUsagePlanRequest createUsagePlanRequest = new CreateUsagePlanRequest()
                .withName(usagePlanName)
                .withDescription("Usage plan for IP traffic limit")
                .withApiStages(new ApiStage().withApiId(apiGatewayId).withStage("prod"));

        return apiGatewayClient.createUsagePlan(createUsagePlanRequest);
    }

    private static void updateUsagePlan(String apiGatewayId, String usagePlanId, String domainName) {
        AmazonApiGateway apiGatewayClient = AmazonApiGatewayClientBuilder.defaultClient();

        GetUsagePlanRequest getUsagePlanRequest = new GetUsagePlanRequest()
                .withUsagePlanId(usagePlanId);

        GetUsagePlanResult getUsagePlanResult = apiGatewayClient.getUsagePlan(getUsagePlanRequest);
        UsagePlan usagePlan = getUsagePlanResult.getItem();

        UsagePlanKey usagePlanKey = new UsagePlanKey()
                .withId(usagePlan.getId())
                .withType("API_KEY")
                .withValue(domainName);

        UpdateUsagePlanRequest updateUsagePlanRequest = new UpdateUsagePlanRequest()
                .withUsagePlanId(usagePlan.getId())
                .withPatchOperations(new PatchOperation().withOp("replace").withPath("/keys").withValue(usagePlanKey));

        UpdateUsagePlanResult updateUsagePlanResult = apiGatewayClient.updateUsagePlan(updateUsagePlanRequest);
    }
}

在上述示例中，首先创建了一个Usage Plan，然后更新了该Usage Plan的API Stage，将其绑定到指定的域名上。这样就可以使用域名来限制API网关的IP流量。注意替换代码中的your-api-gateway-id、your-usage-plan-name和your.domain.name为实际的值。