前台请求的是文件数组，需要下载多个文件 ，java spring boot 从s3下载zip返给前台浏览器，直接浏览器下载

在Spring Boot项目中，如果你需要从Amazon S3下载多个文件并返回给前台浏览器直接下载，你可以这样做：

1. **添加依赖**:
首先，在`pom.xml`中引入AWS SDK for Java (S3客户端) 和 Spring Web相关的依赖：

   <dependency>
       <groupId>com.amazonaws</groupId>
       <artifactId>aws-java-sdk-s3</artifactId>
   </dependency>
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
   </dependency>

2. **配置AWS客户端**:
在`application.properties`或`application.yml`中添加AWS的凭证信息：

   aws.accessKeyId=your_access_key
   aws.secretKey=your_secret_key
   s3.bucketName=your_s3_bucket_name

3. **创建服务类**:
创建一个`S3Service`类，用于获取S3文件并触发下载：

   @Service
   public class S3ServiceImpl implements S3Service {
       private AmazonS3 s3Client;

       @Autowired
       public void setS3Client(AmazonS3 amazonS3) {
           this.s3Client = amazonS3;
       }

       @Override
       public ResponseEntity<byte[]> downloadZip(String[] fileKeys) throws IOException {
           List<S3Object> objects = s3Client.listObjects(BucketRequestBuilder.bucketName(bucketName()).build())
                   .getObjectSummaries()
                   .stream()
                   .filter(obj -> Arrays.asList(fileKeys).contains(obj.getKey()))
                   .collect(Collectors.toList());

           if (objects.isEmpty()) {
               throw new FileNotFoundException("No files found with the given keys.");
           }

           S3Object object = objects.get(0); // Assuming single file per request
           byte[] data = getObjectContent(object);
           HttpHeaders headers = new HttpHeaders();
           headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
           return new ResponseEntity<>(data, headers, HttpStatus.OK);
       }

       private byte[] getObjectContent(S3Object obj) {
           try {
               return obj.getObjectContent().array();
           } catch (IOException e) {
               throw new RuntimeException("Error downloading file from S3.", e);
           }
       }
   }

4. **暴露API**:
在Controller中，通过`@GetMapping`处理GET请求，接收文件键数组，并调用`downloadZip`方法：

   @RestController
   public class FileDownloadController {
       private final S3Service s3Service;

       @Autowired
       public FileDownloadController(S3Service s3Service) {
           this.s3Service = s3Service;
       }

       @GetMapping("/download-zip")
       public ResponseEntity<byte[]> downloadFiles(@RequestParam String[] fileKeys) {
           try {
               return s3Service.downloadZip(fileKeys);
           } catch (Exception e) {
               log.error("Error while downloading zip.", e);
               return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
                       .contentType(MediaType.TEXT_PLAIN)
                       .body(e.getMessage());
           }
       }
   }

5. **浏览器端处理**:
后端返回的响应会被自动设置为`Content-Disposition: attachment`头，浏览器会感知到这是下载内容而不是浏览，所以可以直接下载。