支付宝沙箱调用参数就三个APPID，用户私钥，支付宝公钥，


发送请求需要的配置
alipay:
app_id: 2021000122636644
merchant_private_key: 用户私钥
alipay_public_key: 支付宝公钥
sign_type: RSA2
charset: utf-8
gatewayUrl: https://openapi-sandbox.dl.alipaydev.com/gateway.do

@Setter
@Getter
@Component
@ConfigurationProperties(prefix = "alipay")
public class AlipayProperties {
    //商品应用ID
    private String appId;
    // 商户私钥，您的PKCS8格式RSA2私钥
    private String merchantPrivateKey;
    // 支付宝公钥,查看地址：https://openhome.alipay.com/platform/keyManage.htm 对应APPID下的支付宝公钥。
    private String alipayPublicKey;
    // 签名方式
    private String signType ;
    // 字符编码格式
    private String charset;
    // 支付宝网关
    private String gatewayUrl ;
}

@Configuration
public class AlipayConfig {
    @Bean
    public AlipayClient alipayClient(AlipayProperties alipayProperties){
        return new DefaultAlipayClient(alipayProperties.getGatewayUrl(),
                alipayProperties.getAppId(),
                alipayProperties.getMerchantPrivateKey(),
                "json", alipayProperties.getCharset(),
                alipayProperties.getAlipayPublicKey(),
                alipayProperties.getSignType());
    }
}

@RestController
@RequestMapping("/alipay")
@Slf4j
public class AlipayController {

    @Autowired
    private AlipayProperties alipayProperties;
    @Autowired
    private AlipayClient alipayClient;

    @RequestMapping("/payOnline")
    public Result<String> payOnline(@RequestBody PayVo vo) throws AlipayApiException {
        log.info("支付宝支付页面开始创建");
        //设置请求参数
        AlipayTradePagePayRequest alipayRequest = new AlipayTradePagePayRequest();
        alipayRequest.setReturnUrl(vo.getReturnUrl());
        alipayRequest.setNotifyUrl(vo.getNotifyUrl());

        alipayRequest.setBizContent("{\"out_trade_no\":\""+ vo.getOutTradeNo() +"\","
                + "\"total_amount\":\""+ vo.getTotalAmount() +"\","
                + "\"subject\":\""+ vo.getSubject() +"\","
                + "\"body\":\""+ vo.getBody() +"\","
                + "\"product_code\":\"FAST_INSTANT_TRADE_PAY\"}");

        //post请求
        String html = alipayClient.pageExecute(alipayRequest).getBody();
        log.info(html);
        return Result.success(html);
    }
}

如果你的 gatewayUrl和支付宝网关地址配置不一样
会报错
错误代码 missing-signature-config 错误原因: 应用未配置对应签名算法的公钥或者证书

密钥和公钥不对，注意要首格空格，所有都在一行
调试错误，请回到请求来源地，重新发起请求。
错误代码 invalid-signature 错误原因: 验签出错，建议检查签名字符串或签名私钥与应用公钥是否匹配，网关生成的验签字符串为：alipay_sdk=alipay-sdk-java-4.10.170.ALL&app_id=2021000122636644&charset=utf-8&format=json&method=alipay.trade.page.pay&notify_url=http://8sesy6.natappfree.cc/seckill/orderPay/notify_url&return_url=http://8sesy6.natappfree.cc/seckill/orderPay/return_url&sign_type=RSA2&timestamp=2023-09-09 21:40:02&version=1.0