springboot学习(四十五) springboot下载文件的各种方式

本文主要是介绍springboot学习(四十五) springboot下载文件的各种方式，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

方式一：使用response输出流下载

 	@GetMapping("/t1")public void down1(HttpServletRequest request, HttpServletResponse response) throws Exception {response.reset();response.setContentType("application/octet-stream;charset=utf-8");response.setHeader("Content-disposition","attachment; filename=test.txt");try(BufferedInputStream bis = new BufferedInputStream(new FileInputStream("d:/test.txt"));// 输出流BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream());){
//            bis.transferTo(bos);byte[] buff = new byte[1024];int len = 0;while ((len = is.read(buff)) > 0) {os.write(buff, 0, len);}}}

注意第一种方式返回值必须为void

方式二：使用ResponseEntity

	@GetMapping("/t2")public ResponseEntity<InputStreamResource> down2() throws Exception {InputStreamResource isr = new InputStreamResource(new InputStream("d:/test.txt"));return ResponseEntity.ok().contentType(MediaType.APPLICATION_OCTET_STREAM).header("Content-disposition", "attachment; filename=test.txt").body(isr);}

方式三：使用ResponseEntity

 @GetMapping("/t3")public ResponseEntity<ByteArrayResource> down3() throws Exception {byte[] bytes = Files.readAllBytes(new File("d:/test.csv").toPath());ByteArrayResource bar = new ByteArrayResource(bytes);return ResponseEntity.ok().contentType(MediaType.APPLICATION_OCTET_STREAM).header("Content-disposition", "attachment; filename=test.txt").body(bar);}

方式四：后端使用前三种的一种方式，请求方式使用非GET请求，前端使用Blob类型接收

某些情况下，在下载时需要向后端POST一些参数，这时需要前端做一定配合，将接收类型设定为Blob,并通过JS实现a标签下载
后端代码（这里使用第三种方式为例，前两种也可以）：

@PostMapping("/t4")public ResponseEntity<ByteArrayResource> down4(String fileName, @RequestBody Map data) throws Exception {System.out.println(data);byte[] bytes = Files.readAllBytes(new File("d:/test.csv").toPath());ByteArrayResource bar = new ByteArrayResource(bytes);return ResponseEntity.ok().contentType(MediaType.APPLICATION_OCTET_STREAM).header("Content-disposition", "attachment; filename=test.txt").body(bar);}

前端代码（这里使用了原生的ajax）:

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>function download() {var ajax = new XMLHttpRequest();ajax.withCredentials = true;ajax.responseType = "blob";const fileName = "ttt.txt";ajax.open('post','http://localhost:7901/demo/down/file/t4?fileName=' +  fileName);ajax.setRequestHeader("Content-Type","application/json;charset=utf-8");// ajax.setRequestHeader("Accept","application/json;charset=utf-8");ajax.send(JSON.stringify({firstName:"Bill", lastName:"Gates", age:62, eyeColor:"blue"}));ajax.onreadystatechange = function () {if (ajax.readyState==4 &&ajax.status==200) {console.log(ajax.response);const href = URL.createObjectURL(ajax.response);const a = document.createElement('a');a.setAttribute('href', href);a.setAttribute('download', fileName);a.click();URL.revokeObjectURL(href);}}}</script>
</head>
<body><input type="button" value="下载" onclick="download();"/>
</body>
</html>