因为项目中需要用到微信支付，这里对自己对接的流程做一个记录
一、接入前准备
1.申请应用appId与商户号，配置apiV3秘钥
2.生成商户证书
首先登录微信商家平台，进入"账户中心–>账户设置–>API安全",申请API证书（此证书为商户证书，跟下文的微信平台支付证书不一样），下载安装方式见官方文档
经过上面链接中的教程，你将会在本地得到如下三个文件：
我们将用到apiclient_key.pem文件，为商户私钥
3.生成微信支付平台证书
这一步至关重要，因为很多人接入的时候由于官方文档写的很笼统而忽略此步，再调用API的时候错误的使用的商户证书，导致签名验证微信返回的内容时不成功，而爆出如下的错误：应答的微信支付签名验证失败
关于这个错误，其实只需要按照本文的此步生成微信支付平台证书即可。
3.1下载微信支付平台证书生成工具
下载jar包
3.2.执行命令生成微信支付平台证书
执行:“java -jar CertificateDownloader-1.2.0-jar-with-dependencies.jar -f 商户私钥文件路径 -k 证书解密的密钥 -m 商户号 -o 证书保存路径 -s 商户证书序列号”就行了。
这条命令的参数搞清楚3点：
a）“商户私钥文件路径”是账号中心->API安全->API证书中设置并下载的证书（就是其中的apiclient_key.pem，下载还会获得apiclient_cert.pem，我之前把这个当做支付证书了，其实不是，apiclient_cert.pem这用不着）
b)“商户证书序列号”这个东西也是设置API证书那里知道；
c)“证书解密的密钥”在账号中心->API安全->APIv3密钥中设置的（注意api密钥和apiv3密钥是2个东西）。
执行完了是个类似wechatpay_525846BC3402533386FD3D9DF7C13AA9D3CBBBC4.pem的文件，这个就是微信支付平台证书
**
二、java后台接入微信支付
**
1.引入微信支付服务端sdk
<dependency>
<groupId>com.github.wechatpay-apiv3</groupId>
<artifactId>wechatpay-apache-httpclient</artifactId>
<version>0.4.4</version>
</dependency>
2.创建一个微信支付工具类（我这里是用流的方式加载商户私钥与平台证书文件）
import com.alibaba.fastjson.JSONObject;
import com.wechat.pay.contrib.apache.httpclient.WechatPayHttpClientBuilder;
import com.wechat.pay.contrib.apache.httpclient.util.PemUtil;
import lombok.Data;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.util.EntityUtils;
import org.springframework.stereotype.Component;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Base64;
@Component
@Data
public class WxPayUtil {
public static final String mchId = ""; // 商户号
public static final String appId = ""; // appId
public static final String apiV3Key = ""; // apiV3秘钥
//商户私钥路径
public static final String privateKeyUrl = "";
//平台证书路径
public static final String wechatPayCertificateUrl = "";
//第一步申请完证书后，在API证书哪里点击管理证书就能看到
public static final String mchSerialNo = ""; // 商户证书序列号
private CloseableHttpClient httpClient;
public void setup() {
// PrivateKey merchantPrivateKey = PemUtil.loadPrivateKey(privateKey);
PrivateKey merchantPrivateKey = null;
X509Certificate wechatPayCertificate = null;
try {
merchantPrivateKey = PemUtil.loadPrivateKey(
new FileInputStream(privateKeyUrl));
wechatPayCertificate = PemUtil.loadCertificate(
new FileInputStream(wechatPayCertificateUrl));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
ArrayList<X509Certificate> listCertificates = new ArrayList<>();
listCertificates.add(wechatPayCertificate);
WechatPayHttpClientBuilder builder = WechatPayHttpClientBuilder.create()
.withMerchant(mchId, mchSerialNo, merchantPrivateKey)
.withWechatPay(listCertificates);
httpClient = builder.build();
}
/**
* wxMchid商户号
* wxCertno证书编号
* wxCertPath证书地址
* wxPaternerKey v3秘钥
* url 下单地址
* body 构造好的消息体
*/
public JSONObject doPostWexinV3(String url, String body) {
if (httpClient == null) {
setup();
}
HttpPost httpPost = new HttpPost(url);
httpPost.addHeader("Content-Type", "application/json;chartset=utf-8");
httpPost.addHeader("Accept", "application/json");
try {
if (body == null) {
throw new IllegalArgumentException("data参数不能为空");
}
StringEntity stringEntity = new StringEntity(body, "utf-8");
httpPost.setEntity(stringEntity);
// 直接执行execute方法，官方会自动处理签名和验签，并进行证书自动更新
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
if (httpResponse.getStatusLine().getStatusCode() == 200) {
String jsonResult = EntityUtils.toString(httpEntity);
return JSONObject.parseObject(jsonResult);
} else {
System.err.println("微信支付错误信息" + EntityUtils.toString(httpEntity));
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
//获取签名
public String getSign(String appId, long timestamp, String nonceStr, String pack){
String message = buildMessage(appId, timestamp, nonceStr, pack);
String paySign= null;
try {
paySign = sign(message.getBytes("utf-8"));
} catch (Exception e) {
e.printStackTrace();
}
return paySign;
}
private String buildMessage(String appId, long timestamp, String nonceStr, String pack) {
return appId + "\n"
+ timestamp + "\n"
+ nonceStr + "\n"
+ pack + "\n";
}
private String sign(byte[] message) throws Exception{
PrivateKey merchantPrivateKey = null;
X509Certificate wechatPayCertificate = null;
try {
merchantPrivateKey = PemUtil.loadPrivateKey(
new FileInputStream(privateKeyUrl));
wechatPayCertificate = PemUtil.loadCertificate(
new FileInputStream(wechatPayCertificateUrl));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
Signature sign = Signature.getInstance("SHA256withRSA");
//这里需要一个PrivateKey类型的参数，就是商户的私钥。
sign.initSign(merchantPrivateKey);
sign.update(message);
return Base64.getEncoder().encodeToString(sign.sign());
}
}
2.调用微信app支付下单接口，返回返回预交易prepay_id，通过prepay_id，appid,随机字符串，时间戳，计算得到签名，返回给客户端调起支付
public CommonResult WxPayApp(){
com.alibaba.fastjson.JSONObject amountJson = new com.alibaba.fastjson.JSONObject();
amountJson.put("total",Integer.valueOf(1));
amountJson.put("currency","CNY");
//基础信息json
com.alibaba.fastjson.JSONObject json = new com.alibaba.fastjson.JSONObject();
// json.put("appid","wx043e87691cbad09f");
json.put("appid", WxPayUtil.appId);
json.put("mchid",WxPayUtil.mchId);
json.put("description","测试");
json.put("out_trade_no","1111223344456");
json.put("notify_url","https://www.baidu.com");
json.put("amount",amountJson);
com.alibaba.fastjson.JSONObject jsonObject1 = wxPayUtil.doPostWexinV3("https://api.mch.weixin.qq.com/v3/pay/transactions/app", json.toJSONString());
log.info("结果："+jsonObject1.toJSONString());
String prepay_id = jsonObject1.getString("prepay_id");
//时间戳
Long timestamp = System.currentTimeMillis()/1000;
//随机串
String nonceStr = UUID.randomUUID().toString().replace("-","");
String sign = wxPayUtil.getSign(WxPayUtil.appId,timestamp,nonceStr,prepay_id);
log.info("签名:"+sign);
Map payMap = new HashMap();
payMap.put("prepayid",prepay_id);
payMap.put("timestamp",timestamp+"");
payMap.put("noncestr",nonceStr);
payMap.put("sign",sign);
payMap.put("appid",WxPayUtil.appId);
payMap.put("package","Sign=WXPay");
payMap.put("extData","sign");
payMap.put("partnerid",WxPayUtil.mchId);
return CommonResult.success(payMap);
}
3.微信回调处理，微信会向通过基础下单接口中的请求参数“notify_url”设置的接口地址推送支付结果信息
public void wxCallback(HttpServletRequest request, HttpServletResponse response) throws Exception {
log.info("微信支付回调");
//获取报文
String body = getRequestBody(request);
//随机串
String nonce = request.getHeader("Wechatpay-Nonce");
//微信传递过来的签名
String signature = request.getHeader("Wechatpay-Signature");
//证书序列号（微信平台）
String wechatPaySerial = request.getHeader("Wechatpay-Serial");
//时间戳
String timestamp = request.getHeader("Wechatpay-Timestamp");
PrivateKey merchantPrivateKey = PemUtil.loadPrivateKey(new FileInputStream(WxPayUtil.privateKeyUrl));
// 获取证书管理器实例
CertificatesManager certificatesManager = CertificatesManager.getInstance();
// 向证书管理器增加需要自动更新平台证书的商户信息
certificatesManager.putMerchant(WxPayUtil.mchId, new WechatPay2Credentials(WxPayUtil.mchId,
new PrivateKeySigner(WxPayUtil.mchSerialNo, merchantPrivateKey)),
WxPayUtil.apiV3Key.getBytes(StandardCharsets.UTF_8));
// 从证书管理器中获取verifier
Verifier verifier = certificatesManager.getVerifier(WxPayUtil.mchId);
// 构建request，传入必要参数
NotificationRequest notificationRequest = new NotificationRequest.Builder().withSerialNumber(wechatPaySerial)
.withNonce(nonce)
.withTimestamp(timestamp)
.withSignature(signature)
.withBody(body)
.build();
NotificationHandler handler = new NotificationHandler(verifier, WxPayUtil.apiV3Key.getBytes(StandardCharsets.UTF_8));
// 验签和解析请求体
Notification notification = handler.parse(notificationRequest);
Assert.assertNotNull(notification);
String result = notification.getDecryptData();
log.info("解密报文："+result);
com.alibaba.fastjson.JSONObject resultJson = JSON.parseObject(result);
String trade_state = resultJson.getString("trade_state").trim();
String out_trade_no = resultJson.getString("out_trade_no").trim();
String trade_type = resultJson.getString("trade_type").trim();
log.info("微信支付交易状态码:"+trade_state);
log.info("微信支付交易订单号:"+out_trade_no);
log.info("微信支付交易类型:"+trade_type);
if("SUCCESS".equals(trade_state)){
//支付成功，你的业务逻辑
}
}
}
4.getRequestBody方法
private String getRequestBody(HttpServletRequest request) {
StringBuffer sb = new StringBuffer();
try (ServletInputStream inputStream = request.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
) {
String line;
while ((line = reader.readLine()) != null) {
sb.append(line);
}
} catch (IOException e) {
log.error("读取数据流异常:{}", e);
}
return sb.toString();
}
通过上面的步骤，可以完成微信支付了！! 收工。