Click the button for file downloads

First, use the background

Generally speaking, when we upload a file, the file will be provided to download entrance. And in fact, is to get the file download the file, the file contents are written to process returns HTTP response.

Second, the implementation of the front end

• Form submission form structure

1, related to the introduction js

<script src="${basepath}/jquery-3.3.1/jquery-3.3.1.js" type="text/javascript"></script>
<script src="${basepath}/downLoadFile.js" type="text/javascript" ></script>

jquery-3.3.1 download link address

downLoadFile.js download link address

2, binding on the download button click event

<button οnclick=downLoadFile('"+fileId+"') class='btn btn-info btn-sm pull-right'>下 载</button>

3, downLoadFile.js source

function downLoadFile(id){
	var form=$("<form>");    // 定义一个form表单
	form.attr("style","display:none");
	form.attr("target","_blank");
	form.attr("method","post");
	form.attr("action","/download");    // 此处填写文件下载提交路径
	var input1=$("<input>");
	input1.attr("type","hidden");
	input1.attr("name","id");    // 后台接收参数名
	input1.attr("value",id);
	$("body").append(form);    // 将表单放置在web中
	form.append(input1);
	form.submit();    // 表单提交
}

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Third, the Java implementation of the background section of code

/**
  * 附件下载
  */
@RequestMapping(value = "download")
public String downloadFile( HttpServletRequest request, Model model,HttpServletResponse response, RedirectAttributes redirectAttributes,String id) {
    shareFile = fileService.get(id);
    if(shareFile != null){
        String fileName = shareFile.getFilename().replace(" ", "");
        response.reset();
        response.setContentType("application/octet-stream; charset=utf-8");
        String agent = request.getHeader("USER-AGENT");    // 获取浏览器类型
        String downLoadName = null;  
        try {
            // Edge
            if (null != agent && -1 != agent.indexOf("Edge")) {    
                downLoadName = java.net.URLEncoder.encode(fileName, "UTF-8");
            // Firefox
            } else if (null != agent && -1 != agent.indexOf("Firefox")) {        
                downLoadName = new String(fileName.getBytes("UTF-8"), "iso-8859-1");
            // Chrome或360  
            } else if (null != agent && -1 != agent.indexOf("Chrome")) {        
                downLoadName = new String(fileName.getBytes("UTF-8"), "iso-8859-1");     
            } else {  
                downLoadName = java.net.URLEncoder.encode(fileName, "UTF-8");   
            }   
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } 
        response.setHeader("Content-Disposition", "attachment; filename="+downLoadName);
		
        InputStream in = fileService.downloadFile(shareFile);    // 此处是获取文件输入流 
        OutputStream out;
        try {
            out = response.getOutputStream();
            //写文件  
            int b;  
            while((b = in.read()) != -1) {  
                out.write(b);  
            }
            in.close();  
            out.close();  
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return null;
}

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