二维码生成和显示and下载-优快云博客

本文介绍了一种通过Java后台生成二维码的方法，并详细解释了如何将指定URL和参数编码到二维码中，以及如何从前端请求这些二维码并下载。此外，还提供了具体的代码实现，包括生成二维码的后台逻辑和下载功能。

1.生成二维码方法

@RequiresPermissions("cfm:wCorporateinformationmanagement:edit")
@RequestMapping(value = "produce")
@ResponseBody
public Map<String, String> produce(String id,Model model,HttpServletRequest request) throws Exception{
WCorporateinformationmanagement cfm =wCorporateinformationmanagementService.findByid(id);
String cpn = cfm.getCompanyname();
String dpg =cfm.getDutyparagraph();
name = id;
MultiFormatWriter writer = new MultiFormatWriter();
InetAddress address =InetAddress.getLocalHost();
String localIp = address.getHostAddress();
System.out.println("http://"+localIp+":"+request.getLocalPort() + request.getContextPath());
String ip = "http://"+localIp+":"+request.getLocalPort()+ request.getContextPath()+"/f"+"/user/wUser/login"+"?companyname="+cpn+"&dutyparagraph="+dpg;
String contents = id;
int w = 200;
int h = 200;
HashMap<EncodeHintType, Object> Hints = new HashMap<EncodeHintType, Object>();
Hints.put(EncodeHintType.CHARACTER_SET, "utf-8");
//二进制矩阵数据
BitMatrix bitMatrix = writer.encode(contents, BarcodeFormat.QR_CODE, w, h,Hints);
//本身提提供的类
//MatrixToImageWriter.writeToPath(bitMatrix, "png", new File("F:/1.png").toPath());
BufferedImage qr = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
for(int x=0;x<w;x++) {
for(int y = 0;y<h;y++) {
if(bitMatrix.get(x, y)) {
qr.setRGB(x, y, 0x000000);
}else {
qr.setRGB(x, y, 0xFFFFFF);
}
}
}
String url = request.getSession().
getServletContext().getRealPath("/")+"uploadFile\\"+new Date().getTime()+".png";
File file = new File(url);
if(!file.exists()){
file.mkdirs();
}
String top = request.getContextPath();
String top1 = top.substring(1,top.length());
String top2 = "";
top2 ="\\" + top1.substring(0,top1.length());
ImageIO.write(qr, "png", new File(url));
String newurl = url.substring(url.indexOf(top2),url.length());
Map<String, String> map = new HashMap<String, String>();
map.put("image", newurl);
map.put("url", url);

return map;
}

1.1

动态的显示url，和把需要的参数保存到二维码。

1.2

用url保存二维码的路径

1.3

这是生成二维码的方法。

2.1前台用js接受生成二维码按键

2.2用Ajax写好要传的参数和路径

3.1 接收生成二维码方法返回的值。

用键值对分别把显示图片路径和下载路径传到前台

data就表示接收到的map。

3.2用jbox弹框显示图片

然后把用a标签跳转到download方法上并把下载图片需要的动态名字和下载路径两个参数带过去

4.1 download方法

@RequestMapping(value = "/download")
public String download(@RequestParam String name,@RequestParam String url, HttpServletResponse response, HttpServletRequest request) throws Exception{
System.out.println("==========================");
System.out.println("开始下载");
InputStream in = null ;
OutputStream out = null ;
try
{
in = new FileInputStream(url); //获取文件的流
int len = 0;
byte buf[] = new byte[1024];//缓存作用
response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(name + ".png", "UTF-8"));
out = response.getOutputStream();//输出流
while( (len = in.read(buf)) > 0 ) //切忌这后面不能加分号 ”;“
{
out.write(buf, 0, len);//向客户端输出，实际是把数据存放在response中，然后web服务器再去response中读取
}

in.close();
out.close();

}finally{
//TODO
}
return null;
}