Java接收并上传图片至S3，返回图片URL，并删除本地图片

待我称王封你为后i 2023-01-24 02:25 54阅读 0赞

**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file
            MultipartFile 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
    @PostConstruct
        public 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。**