[Java]微信支付apiv3接入demo 复制可用(jsapi 小程序)

若干年前接过微信和支付宝，当时微信还是xml，接完以后当时就觉着微信的接口弄的烂的一批，，，。最近又有接入微信支付，相比之前好了一点吧，但是感觉微信还是弄的太散乱了。

以下内容仅为减少代码的重复劳动，并不提供接入流程、字段、配置说明，开始前请明确已经阅读过微信支付文档，了解接入流程，并获取了秘钥证书相关内容

包含的接口有，jsapi下单、小程序调起支付加签、回调数据处理、微信支付平台证书更新。功能包括数据加验签，加解密

代码中注意使用官方类库，以保证资金安全。当前为2021年8月，时间久远内容可能出现差异，注意识别

maven引入微信支付sdk

<dependency>
    <groupId>com.github.wechatpay-apiv3</groupId>
    <artifactId>wechatpay-apache-httpclient</artifactId>
    <version>0.2.2</version>
</dependency>

aes解密方法(AesUtil)直接复制官方示例

import java.io.IOException;
import java.security.GeneralSecurityException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AesUtil {
   
   

	static final int KEY_LENGTH_BYTE = 32;
	static final int TAG_LENGTH_BIT = 128;
	private final byte[] aesKey;

	public AesUtil(byte[] key) {
   
   
		if (key.length != KEY_LENGTH_BYTE) {
   
   
			throw new IllegalArgumentException("无效的ApiV3Key，长度必须为32个字节");
		}
		this.aesKey = key;
	}

	public String decryptToString(byte[] associatedData, byte[] nonce, String ciphertext)
	throws GeneralSecurityException, IOException {
   
   
		try {
   
   
			Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");

			SecretKeySpec key = new SecretKeySpec(aesKey, "AES");
			GCMParameterSpec spec = new GCMParameterSpec(TAG_LENGTH_BIT, nonce);

			cipher.init(Cipher.DECRYPT_MODE, key, spec);
			cipher.updateAAD(associatedData);

			return new String(cipher.doFinal(Base64.getDecoder().decode(ciphertext)), "utf-8");
		} catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
   
   
			throw new IllegalStateException(e);
		} catch (InvalidKeyException | InvalidAlgorithmParameterException e) {
   
   
			throw new IllegalArgumentException(e);
		}
	}
}

参数配置类

public class WeiXinProties {
   
   
    @Getter
    private static final String APP_ID = "微信小程序APPID";
    @Getter
    private static final String MERC_ID = "微信支付商户号";
    @Getter
    private static final String SECRET = "微信小程序安全码";
    @Getter
    private static final String SERIAL_NO = "微信支付证书编号";
    @Getter
    private static final String PRIVATE_KEY = "微信支付证书私钥，就是下载的apiclient_key.pem内容，去掉头尾换行";
    @Getter
    private static final String NOTIFY_URL = "支付结果回调地址";
    @Getter
    private static final String WEIXINPAY_URL = "https://api.mch.weixin.qq.com/v3/pay/transactions/jsapi";//微信jsapi下单地址
    @Getter
    private static final String APIV3_KEY = "apiv3秘钥";
    @Getter
    private static final String API_KEY = "api秘钥，新版本v3接口好像没用";