Controller主入口：

[code]
/**
* 创建二维码
*/
@RequestMapping("createQRCode")
public void createQRCode(String orderId, HttpServletResponse response) {

//生成订单
String orderInfo = createOrderInfo(orderId);
//调统一下单API
String code_url = httpOrder(orderInfo);
//将返回预支付交易链接（code_url）生成二维码图片
//这里使用的是zxing <span style="color:#ff0000;"><strong>说明1(见文末)</strong></span>
try {
int width = 200;
int height = 200;
String format = "png";
Hashtable hints = new Hashtable();
hints.put(EncodeHintType.CHARACTER_SET, "utf-8");
BitMatrix bitMatrix = new MultiFormatWriter().encode(code_url, BarcodeFormat.QR_CODE, width, height, hints);
OutputStream out = null;
out = response.getOutputStream();
MatrixToImageWriter.writeToStream(bitMatrix, format, out);
out.flush();
out.close();
} catch (Exception e) {
}

} [/code]

生成订单:分两部分：一部分是业务需求的订单信息，就是发起支付前的订单信息，业务系统自行创建存储；另一部分是满足统一下单API要求的订单信息（也是我们这里要讲的）。“xxxxxx”:是你需要自己填写的对应信息：
[code] /**
* 生成订单
* @param orderId
* @return
*/
private String createOrderInfo(String orderId) {
//生成订单对象
UnifiedOrderRequest unifiedOrderRequest = new UnifiedOrderRequest();
unifiedOrderRequest.setAppid("xxxxxxxxxxxxx");//公众账号ID
unifiedOrderRequest.setMch_id("xxxxxxxxx");//商户号
unifiedOrderRequest.setNonce_str(StringUtil.makeUUID());//随机字符串 <span style="color:#ff0000;"><strong>说明2(见文末)</strong></span>
unifiedOrderRequest.setBody("xxxxxx");//商品描述
unifiedOrderRequest.setOut_trade_no(orderId);//商户订单号
unifiedOrderRequest.setTotal_fee("x"); //金额需要扩大100倍:1代表支付时是0.01
unifiedOrderRequest.setSpbill_create_ip("xxxxxxxxxxxxx");//终端IP
unifiedOrderRequest.setNotify_url("xxxxxxxxxxxxxx");//通知地址
unifiedOrderRequest.setTrade_type("NATIVE");//JSAPI--公众号支付、NATIVE--原生扫码支付、APP--app支付
unifiedOrderRequest.setSign(createSign(unifiedOrderRequest));//签名<span style="color:#ff0000;"><strong>说明5(见文末，签名方法一并给出)</strong></span>
//将订单对象转为xml格式
XStream xStream = new XStream(new XppDriver(new XmlFriendlyNameCoder("_-", "_"))); //<span style="color:#ff0000;"><strong>说明3(见文末)</strong></span>
xStream.alias("xml", UnifiedOrderRequest.class);//根元素名需要是xml
return xStream.toXML(unifiedOrderRequest);
} [/code]