Java将图片上传至S3，一般前端页面上传过来的图片，在后端接收形式都为MultipartFile，而S3不支持MultipartFile形式的文件，只支持File类型，所以需要先转换类型再上传。注意：由于上传成功后，本地或者代码运行服务器中图片也会存在，为避免这个问题，上传成功需要本地删除图片。完整代码如下：
（只需要将下面Service中开始部分的变量改成你自己的就可以直接使用）
Controller：
//上传图片@PostMapping("/uploadPicture")public String uploadPicture(HttpServletRequest request) {MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;// 前端传过来的图片参数名为fileMultipartFile multipartFileImageFile = multipartRequest.getFile("file");return uploadService.uploadPicture(multipartFileImageFile);}
Service:
// 需要将这些变量改成你自己的，若只放到桶的根目录下，picturePath设为空private String AWS_ACCESS_KEY = "xxxxxxxxxx";private String AWS_SECRET_KEY = "xxxxxxxxxx";private String region = "xxxx";private String bucketName = "myBucket";private String picturePath = "/picture/mypng"// 初始化连接S3@PostConstructpublic void init() {BasicAWSCredentials basicAWSCredentials = new BasicAWSCredentials(AWS_ACCESS_KEY, AWS_SECRET_KEY);s3 = AmazonS3ClientBuilder.standard().withRegion(region).withCredentials(new AWSStaticCredentialsProvider(basicAWSCredentials)).build();}public String uploadPicture(MultipartFile multipartFileTrayImageFile) {// 调用toFile方法将MultipartFile类型转换为File类型File file = toFile(multipartFileTrayImageFile);String fileUrl = "";long nowTime = System.currentTimeMillis();try {// 调用uploadToS3上传S3并获得图片URL,采用时间戳加文件名字命名，防止命名重复fileUrl = uploadToS3(file, nowTime + "_" + file.getName());// 注意！上传成功后删除，不占用本地或者服务器资源file.delete();} catch (IOException e) {e.printStackTrace();}return fileUrl;}private String uploadToS3(File tempFile, String key) throws IOException {try {String bucketPath = bucketName + floderName;//想要通过公网访问到图片，除了将桶的权限更改之外，还需要在代码中设置withCannedAcl(CannedAccessControlList.PublicRead)s3.putObject(new PutObjectRequest(bucketPath, key, tempFile).withCannedAcl(CannedAccessControlList.PublicRead));String url = cdn + key;return url;} catch (AmazonServiceException ase) {ase.printStackTrace();} catch (AmazonClientException ace) {ace.printStackTrace();}return null;}private File toFile(MultipartFile file) {File toFile = null;if ("".equals(file) || file.getSize() <= 0) {return null;} else {InputStream ins = null;try {ins = file.getInputStream();toFile = new File(file.getOriginalFilename());inputStreamToFile(ins, toFile);ins.close();} catch (IOException e) {e.printStackTrace();}}return toFile;}private static void inputStreamToFile(InputStream ins, File file) {try {OutputStream os = new FileOutputStream(file);int bytesRead = 0;byte[] buffer = new byte[8192];while ((bytesRead = ins.read(buffer, 0, 8192)) != -1) {os.write(buffer, 0, bytesRead);}os.close();ins.close();} catch (Exception e) {e.printStackTrace();}}
非常方便，粘贴后，将需要改的变量修改成自己的就可以直接使用！有问题评论，看到第一时间回复。
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