RestTemplate实现文件上传和下载接口

0 背景

项目中需要调用第三方导入文件和导出文件接口，本文采用RestTemplate调用接口

1 导入文件

// 导入文件
RestTemplate restTemplate = new RestTemplate();
String file = "d:\\test.zip";     //或者File类型文件
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.MULTIPART_FORM_DATA);
MultiValueMap map = new LinkedMultiValueMap<>(2);   //需要MultiValueMap数据结构
map.add("key","value");
map.add("file",new FileSystemResource(file));   //需要FileSystemResource将路径转为文件
HttpEntity> request = new HttpEntity<>(map,headers);
ResponseEntity response = restTemplate.postForEntity(url,request,String.class);

2 导出文件

// 导出文件
String var1 = "";   //url包含的路径参数
File file1 = restTemplate.execute(url,HttpMethod.GET,clientHttpRequest ->{
    HttpHeaders headers1 = new HttpHeaders();
    headers1.add("content-type","application/zip");
    headers1.add("content-disposition","attachment; filename=export-single.zip");   //添加头文件
},clientHttpResponse -> {
    File ret = File.createTempFile("export",".zip");  //生成导出文件的命名（"export"+"随机字符"+".zip"）
    StreamUtils.copy(clientHttpResponse.getBody(), new FileOutputStream(ret));
    return ret;
},var1);


// 导出文件之后到浏览器直接下载
 HttpHeaders httpHeaders = new HttpHeaders();
 httpHeaders.setContentDispositionFormData("attachment",file1.getName());
 return new ResponseEntity(new FileSystemResource(file),httpHeaders,HttpStatus.OK);

3 将一个java对象转化为json字符串并下载

// 使用工具 fastjson
//已有对象 user
InputStream inputStream = new ByteArrayInputStream(JSONArray.toJSONString(user).getBytes());   //fastjson将java对象转化为json字符串
//需要处理异常
File ret = File.createTempFile("export",".json");  //生成导出文件的命名（"export"+"随机字符"+".json"）
StreamUtils.copy(inputStream , new FileOutputStream(ret));
// 浏览器直接下载
 HttpHeaders httpHeaders = new HttpHeaders();
 httpHeaders.setContentDispositionFormData("attachment",ret.getName());
 return new ResponseEntity(new FileSystemResource(file),httpHeaders,HttpStatus.OK);