Java实现小程序微信支付

小程序支付流程交互图：

进入小程序，下单，请求下单支付，调用小程序登录API来获取Openid，生成商户订单

// pages/pay/pay.js 
var app = getApp(); 
Page({ 
    data: {}, 
    onLoad: function (options) { 
        // 页面初始化 options为页面跳转所带来的参数 
    }, 
    /* 微信支付 */ 
    wxpay: function () { 
        var that = this;
        //登陆获取code 
        wx.login({ 
            success: function (res) { 
                //获取openid 
                that.getOpenId(res.code); 
            } 
        }); 
    }, 
    getOpenId: function (code) { 
        var that = this; 
        wx.request({ 
            url: "https://api.weixin.qq.com/sns/jscode2session?appid=小程序appid&secret=小程序Secret&js_code=" + code + "&grant_type=authorization_code", 
            data: {}, 
            method: 'GET', 
            success: function (res) { 
                console.log(res.data); 
                that.generateOrder(res.data.openid); 
            }, 
            fail: function () { 
                // fail 
            }, 
            complete: function () { 
                // complete 
            } 
        }) 
    }, 
    /**生成商户订单 */ 
    generateOrder: function (openid) { 
        var that = this; 
        //统一支付 
        wx.request({ 
            url: 'http://localhost:9090/weixin/payment.do', 
            method: 'GET', 
            data: { 
                total_fee: '666', //金额，注意以分为单位
                body: '茅台', //产品简单描述
                attach:'广州分店' //附加数据
            }, 
            success: function (res) { 
                var pay = res.data 
                //发起支付 
                var timeStamp = pay[0].timeStamp; 
                var packages = pay[0].package; 
                var paySign = pay[0].paySign; 
                var nonceStr = pay[0].nonceStr; 
                var param = { "timeStamp": timeStamp, "package": packages, "paySign": paySign, "signType": "MD5", "nonceStr": nonceStr }; 
                that.pay(param); 
            }, 
        }) 
    }, 
    /* 支付   */ 
    pay: function (param) { 
        wx.requestPayment({ 
            timeStamp: param.timeStamp, 
            nonceStr: param.nonceStr, 
            package: param.package, 
            signType: param.signType, 
            paySign: param.paySign, 
            success: function (res) { 
                wx.navigateBack({ 
                    delta: 1, // 回退前 delta(默认为1) 页面 
                    success: function (res) { 
                        wx.showToast({ 
                            title: '支付成功', 
                            icon: 'success', 
                            duration: 2000 
                        }) 
                    }, 
                    fail: function () { 
                        // fail 
                    }, 
                    complete: function () { 
                        // complete 
                    } 
                }) 
            }, 
            fail: function (res) { 
                // fail 
                console.log("支付失败"); 
            }, 
            complete: function () { 
                // complete 
                console.log("pay complete"); 
            } 
        }) 
    } 
}) 

调用支付统一下单API来获取prepay_id，并将小程序调起支付数据需要签名的字段appId，timeStamp，nonceStr，package再次签名

后台代码

package com.card.mp.controller;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.card.dto.PaymentDto;
import com.card.framework.utils.*;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Controller
public class WeiXinPaymentController extends BaseController {
    private final String mch_id = "填写商户号";//商户号
    private final String spbill_create_ip = "填写终端IP";//终端IP
    private final String notify_url = "域名/weixin/paycallback.do";//通知地址
    private final String trade_type = "JSAPI";//交易类型
    private final String url = "https://api.mch.weixin.qq.com/pay/unifiedorder";//统一下单API接口链接
    private final String key = "&key=填写商户支付密钥"; // 商户支付密钥
    private final String appid = "填写小程序AppId";

    /**
     *
     * @param openId
     * @param total_fee 订单总金额，单位为分。
     * @param body  商品简单