请帮我用java语言实现苹果内购凭证校验

以下是使用 Java 语言实现苹果内购凭证校验的示例代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.Signature;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

public class AppleIAPVerifier {
    private static final String VERIFY_URL_SANDBOX = "https://sandbox.itunes.apple.com/verifyReceipt";
    private static final String VERIFY_URL_PRODUCTION = "https://buy.itunes.apple.com/verifyReceipt";
    private static final String PUBLIC_KEY = "-----BEGIN PUBLIC KEY-----\n" +
            "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwz5s2CZqWZ8XUq9gHmFW\n" +
            "Wmzr1KcEy5OoN6X1F3V0GxJ8Zk7j/3e3GZvZfNQXfI9Bzib+4d3PZx4iYRh9v6a\n" +
            "FqN1rQcH2u6GZ8fJX/5Z0D5JF5VJyE49vG3Mj92g2yZvLc3tNtWvqgDfZK2p+3kR\n" +
            "6wVxXWpdKK9LSqAIQyN+7qY8Z8DZ8x1v8yJ0TtqJ0IbYj5I+U6QHwvquA1qDhZfJ\n" +
            "EJQgjKQ4nO1NcH972WtD2OA8lBJoK4Wwbj7aL7Lw3l5P3iK6u5nJuy7Nt5m+J5j\n" +
            "z0LVD8cLHcJv9FJ8fT0F4KW7ZE2/+XZ5Xe3N5GW8QIe8DpOmDkL4zq+GQaZ5CqJv\n" +
            "owIDAQAB\n" +
            "-----END PUBLIC KEY-----";

    public static void main(String[] args) throws Exception {
        String receiptData = "replace_with_your_receipt_data";
        boolean sandbox = true; // 是否为沙盒环境

        verifyReceipt(receiptData, sandbox);
    }

    public static void verifyReceipt(String receiptData, boolean sandbox) throws Exception {
        String urlString = sandbox ? VERIFY_URL_SANDBOX : VERIFY_URL_PRODUCTION;
        URL url = new URL(urlString);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        connection.setDoOutput(true);

        String payload = String.format("{\"receipt-data\":\"%s\"}", receiptData);
        connection.getOutputStream().write(payload.getBytes());

        BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        StringBuilder response = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            response.append(line);
        }
        reader.close();

        // 解析返回的 JSON 数据
        JsonObject json = new JsonParser().parse(response.toString()).getAsJsonObject();
        int status = json.get("status").getAsInt();
        if (status == 0) {
            // 验证通过
            System.out.println("Receipt verification succeeded!");
        } else {
            // 验证失败
            System.out.println("Receipt verification failed!");
        }
    }

    public static boolean verifySignature(String receiptData, String signature) throws Exception {
        // 解码公钥
        byte[] publicKeyBytes = Base64.getDecoder().decode(PUBLIC_KEY);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKeyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey publicKey = keyFactory.generatePublic(keySpec);

        // 计算签名
        Signature sig = Signature.getInstance("SHA1withRSA");
        sig.initVerify(publicKey);
        sig.update(receiptData.getBytes());
        byte[] signatureBytes = Base64.getDecoder().decode(signature);

        // 验证签名
        return sig.verify(signatureBytes);
    }
}

此处使用了 Java 标准库中的 `java.security` 包来进行数字签名验证，以及 Google 提供的 `gson` 库来解析 JSON 数据。在代码中，`verifyReceipt` 方法会向苹果服务器发送验证请求，并解析返回的 JSON 数据，从中获取验证结果；而 `verifySignature` 方法则用于验证收据的数字签名，以确保它是由苹果签发的。在实际使用时，可以将这些方法集成到自己的应用中，以实现内购凭证的校验。