js

function _es_preDownload(id, fileName) {
	$.ajax({
		url: ‘${ctx}/fdAttach/download‘,
		type: ‘get‘,
		async: false,
		mimeType: ‘text/plain; charset=x-user-defined‘,//jq ajax请求文件流的方式  （起作用的重点）
		data: {id: id},
		success: function (data) {
			if (data.code && data.code != Ajax.statusCode.ok) {
				Dialog.error(data.message);
				return;
			}

			Dialog.success("下载成功！");
			var rawLength = data.length;
			var array = new Uint8Array(new ArrayBuffer(rawLength));
			for (i = 0; i < rawLength; i++) {
				array[i] = data.charCodeAt(i) & 0xff;
			}
			//上面是把后台请求到的文件流进行转化为符合的流
			var blob = new Blob([array]);
			var fileName = ‘PDF‘+new Date().getTime()+‘.pdf‘;
			if(‘download‘ in document.createElement(‘a‘)){
				//非IE下载
				const elink = document.createElement(‘a‘);
				elink.download=fileName;
				elink.style.display=‘none‘;
				elink.href = URL.createObjectURL(blob);
				document.body.appendChild(elink);
				elink.click();
				URL.revokeObjectURL(elink.href);
				document.body.removeChild(elink);
			}else {
				navigator.msSaveBlob(blob,fileName);
			}

		}
	});
	return false;
}

java

@RequestMapping("/download")
public void download(String id, HttpServletResponse response)
    throws Exception {
    FileInfo fileInfo = fdAttachService.download(id);
    InputStream is = fileInfo.getInputStream();
    response.setContentType("application/force-download");
    IOUtils.copy(is, response.getOutputStream());
}

ajax文件下载