java调用微信小程序统一下单接口

asfx站长

2020.10.11 09:41:51 阅读 910

这是对接微信支付的开发文档地址
https://pay.weixin.qq.com/wiki/doc/api/wxa/wxa_api.php?chapter=7_4&index=3

小程序支付的交互图如下：
[![小程序支付交互图](https://pay.weixin.qq.com/wiki/doc/api/img/wxa-7-2.jpg "小程序支付交互图")](https://pay.weixin.qq.com/wiki/doc/api/img/wxa-7-2.jpg "小程序支付交互图")

##### 流程分析：
我们可以看到，前端人员只用给我们一个code，我们通过code去获取用户openId，然后生成订单，再调用微信支付统一下单API，微信返回给我们一个prepay_id,我们封装起来一起返给前端即可，前端支付成功了，微信会发送通知给我们的回调地址，我们更新订单状态即可，大致流程就是这样，这里主要讲的就是调用统一下单API返回prepay_id的过程

代码：
```java
/**
     * 支付接口
     *
     * @param code     前端传的只能用一次的code
     * @param oderInfo 订单信息接口
     * @param response 响应
     * @return ResultInfo 统一结果集
     */
    @RequestMapping(value = "/weChat/getPrePayId/{code}")
    @ResponseBody
    @ApiOperation(value = "调用微信支付统一下单接口", notes = "调用微信支付统一下单接口", httpMethod = "POST")
    public ResultInfo getPrePayId(@PathVariable(value = "code") String code,
                                          @ApiParam(name = "oderInfo", value = "订单详细信息", required = true)
                                          @RequestBody OrderBO oderInfo,
                                          HttpServletResponse response) {
        response.addHeader("Access-Control-Allow-Origin", "*");
        ResultInfo resultInfo = new ResultInfo();
        //通过code获取openId
        JSONObject openIdResult;
        try {
            openIdResult = (JSONObject) WechatUtil.getMpAccessToken(code);
            if (null == openIdResult) {
                resultInfo.setMsg("结果解析为空！");
                resultInfo.setCode(15115);
                return resultInfo;
            }
        } catch (JSONException e) {
            resultInfo.setMsg("结果解析不正确！");
            resultInfo.setCode(15114);
            return resultInfo;
        }
        String openId = openIdResult.getString("openid");
        if (StringUtil.isEmpty(openId)) {
            resultInfo.setMsg("获取用户openId出错，获得空的openId！");
            resultInfo.setCode(15114);
            return resultInfo;
        }
        // TODO 生成订单的业务代码...

SortedMap<String, String> params = new TreeMap<>();
        //生成32位随机数
        String nonce_str = create_nonce_str().replace("-", "");
        String timestamp = create_timestamp();
        //商户的秘钥，在https://pay.weixin.qq.com 中获取
        String apiKey = ConstantWeChat.API_KEY;
        //小程序ID
        params.put("appid", ConstantWeChat.APPID);
        //商户号
        params.put("mch_id", ConstantWeChat.MCH_ID);
        //openId
        params.put("openid", openId);
        //商品描述
        params.put("body", "APP body");
        //随机字符串，要求在32位以内
        params.put("nonce_str", nonce_str);
        //回调地址
        params.put("notify_url","http://");
        //订单号
        params.put("out_trade_no", oderInfo.getOrderId());
        //终端ip,调用微信支付API的机器IP，即本机的ip
        params.put("spbill_create_ip", "");
        //支付金额,total_fee传的单位是分，不能有小数点
        int totalFee = (int) (oderInfo.getPayAmount() * 100);
        params.put("total_fee", String.valueOf(totalFee));
        //交易类型，小程序取值如下：JSAPI
        params.put("trade_type", "JSAPI");
        //生成签名
        String sign = WechatUtil.createSign(params, apiKey);
        params.put("sign", sign);
        String prepayId = null;
        String wxResult = null;
        try {
            // 将post的数据转换从xml格式
            String xmlObj = WechatUtil.parseXML(params);
            wxResult = WechatUtil.sendPost(HttpClients.createDefault(),
                    "https://api.mch.weixin.qq.com/pay/unifiedorder", xmlObj);
            // 解析xml获取prepayId
            // 记得引入dom4j的依赖
            Document doc = DocumentHelper.parseText(wxResult);
            //objMap 的大小为10的时候就是调用成功了
            Map<String, Object> objMap = WechatUtil.dom2Map(doc);
            String returnCode = (String) objMap.get("return_code");
            String resultCode = (String) objMap.get("result_code");
            if ("SUCCESS".equals(returnCode) && "SUCCESS".equals(resultCode)) {
                prepayId = (String) objMap.get("prepay_id");
            }
            params.put("package", "prepay_id=" + prepayId);
            params.put("timestamp", timestamp);
        } catch (Exception e) {
            resultInfo.setMsg("解析错误！");
            resultInfo.setCode(15114);
            return resultInfo;
        }
        if (null == prepayId) {
            resultInfo.setMsg("解析有误！");
            resultInfo.setCode(15114);
            return resultInfo;
        }
        SortedMap<String, String> params2 = new TreeMap<>();
        params2.put("appId", params.get("appid"));
        params2.put("timeStamp", params.get("timestamp"));
        params2.put("nonceStr", params.get("nonce_str"));
        params2.put("package", "prepay_id=" + prepayId);
        params2.put("signType", "MD5");
        String sign2 = WechatUtil.createSign(params2, apiKey);
        params2.put("paySign", sign2);
        resultInfo.setData(params2);
        resultInfo.setMsg("获取准备ID成功！");
        return resultInfo;
    }

private static String create_nonce_str() {
        return UUID.randomUUID().toString();
    }

private static String create_timestamp() {
        return Long.toString(System.currentTimeMillis() / 1000);
    }
```

用到的公共包：
```java
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONException;
import com.alibaba.fastjson.JSONObject;
import io.swagger.annotations.ApiOperation;
import io.swagger.annotations.ApiParam;
import org.apache.commons.lang.RandomStringUtils;
import org.apache.http.impl.client.HttpClients;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletResponse;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.UUID;
```

maven依赖：
```xml

<dependency>
	<groupId>dom4j</groupId>
	<artifactId>dom4j</artifactId>
	<version>1.6.1</version>
</dependency>
```

WechatUtil工具类：
```java
/**
	 * 生成微信支付签名
	 *
	 * @param parameters 参数
	 * @param apiKey     商户秘钥
	 * @return String
	 */
	public static String createSign(SortedMap<String, String> parameters,
									String apiKey) {

StringBuffer sb = new StringBuffer();
		Set es = parameters.entrySet();
		Iterator it = es.iterator();
		while (it.hasNext()) {
			Map.Entry entry = (Map.Entry) it.next();
			String k = (String) entry.getKey();
			Object v = entry.getValue();
			if (null != v && !"".equals(v) && !"sign".equals(k)
					&& !"key".equals(k)) {
				sb.append(k + "=" + v + "&");
			}
		}
		// 最后加密时添加商户密钥，由于key值放在最后，所以不用添加到SortMap里面去，单独处理，编码方式采用UTF-8
		sb.append("key=" + apiKey);
		try {
			String sign = MD5.encrypt(sb.toString(), "UTF-8").toUpperCase();
			return sign;
		} catch (Exception e) {

}
		return null;
	}

public static String parseXML(SortedMap<String, String> parameters) {
		StringBuffer sb = new StringBuffer();
		sb.append("<xml>");
		Set es = parameters.entrySet();
		Iterator it = es.iterator();
		while (it.hasNext()) {
			Map.Entry entry = (Map.Entry) it.next();
			String k = (String) entry.getKey();
			String v = (String) entry.getValue();
			if (null != v && !"".equals(v) && !"appkey".equals(k)) {
				sb.append("<" + k + ">" + parameters.get(k) + "</" + k + ">\n");
			}
		}
		sb.append("</xml>");
		return sb.toString();
	}
public static String sendPost(CloseableHttpClient httpclient, String url, String xmlObj) throws IOException {
		String result;
		HttpPost httpPost = new HttpPost(url);
		// 得指明使用UTF-8编码，否则到API服务器XML的中文不能被成功识别
		StringEntity postEntity = new StringEntity(xmlObj, "UTF-8");
		httpPost.addHeader("Content-Type", "text/xml");
		httpPost.setEntity(postEntity);
		log.info(xmlObj);
		try {
			CloseableHttpResponse response = httpclient.execute(httpPost);
			try {
				HttpEntity entity = response.getEntity();
				result = EntityUtils.toString(entity, "UTF-8");
			} finally {
				response.close();
			}
		} finally {
			httpclient.close();
		}
		return result;
	}

public static Map<String, Object> dom2Map(Document doc) {
		Map<String, Object> map = new HashMap<>(16);
		if (doc == null) {
			return map;
		}
		Element root = doc.getRootElement();
		for (Iterator iterator = root.elementIterator(); iterator.hasNext(); ) {
			Element e = (Element) iterator.next();
			List list = e.elements();
			if (list.size() > 0) {
				map.put(e.getName(), dom2Map((Document) e));
			} else {
				map.put(e.getName(), e.getText());
			}
		}
		return map;
	}
```

参数校验地址：
```java
//检验发送参数是否规范的地址
https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=20_1
```