Spring Boot中4种文件下载方法的实现
大约 5 分钟
本篇文章介绍Spring Boot中分别返回ResponseEntity<InputStreamResource>、ResponseEntity<Resource>、ResponseEntity<StreamingResponseBody>、HttpServletResponse.getOutputStream()4种文件下载方法的实现。
先看看Controller比较直观的展示效果：
@RestController
@RequestMapping("v1/api/file")
public class FileController {
// spring 注入泛型接口实现
private final DownLoadFileService<InputStreamResource> isrDownLoadFileService;
private final DownLoadFileService<Resource> rDownLoadFileService;
private final DownLoadFileService<StreamingResponseBody> srbDownLoadFileService;
private final DownLoadFileService srDownLoadFileService;
public FileController(DownLoadFileService<InputStreamResource> isrDownLoadFileService, DownLoadFileService<Resource> rDownLoadFileService, DownLoadFileService<StreamingResponseBody> srbDownLoadFileService, DownLoadFileService srDownLoadFileService) {
this.isrDownLoadFileService = isrDownLoadFileService;
this.rDownLoadFileService = rDownLoadFileService;
this.srbDownLoadFileService = srbDownLoadFileService;
this.srDownLoadFileService = srDownLoadFileService;
}
@RequestMapping(value = "/download1", method = RequestMethod.GET,produces = {MediaType.APPLICATION_OCTET_STREAM_VALUE})
@SneakyThrows
public ResponseEntity<InputStreamResource> downloadFile1(String id){
return isrDownLoadFileService.downloadFile(id);
}
@RequestMapping(value = "/download2", method = RequestMethod.GET, produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
@SneakyThrows
public ResponseEntity<Resource> downloadFile2(String id) {
return rDownLoadFileService.downloadFile(id);
}
@GetMapping(value = "/download3", produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
public ResponseEntity<StreamingResponseBody> downloadFile3(@RequestParam(name = "id") String id) {
return srbDownLoadFileService.downloadFile(id);
}
@GetMapping(value = "/download4")
public void downloadFile4(@RequestParam(name = "id") String id) {
srDownLoadFileService.downloadFile(id);
}
}
前言
springboot：2.3.9.RELEASE
mybatis-plus: 3.5.2
本文的文件访问依赖使用minioClient，所有的InputStream都来自minioTemplate.get(thirdFile.getName());，篇幅有限，访问minio具体实现也比较简单就不在本文中介绍，也可以使用其它方式比如本地文件获取文件输入流InputStream。
其实本文介绍的这几种方式原理都是一样的，最终都是往HttpServletResponse输出流，由此还可以做出更多的变通，比如还可以返回ResponseEntity<ByteArrayResource> 、ResponseEntity<byte[]>等，这里可以去看看ResponseEntity的原理：
ResponseEntity对应一个http请求或者响应，可以用在controller的返回值里，方便处理header及status。而通常使用的@ResponseBody注解，只能处理body部分。这也是为什么通常在下载场景中会使用ResponseEntity，因为下载需要设置header里的content-type以及特殊的status（比如206）。
ResponseEntity类型的返回值由一个特殊的HttpEntityMethodProcessor类型的returnTypeHandler来处理，主要是将ResponseEntity里设置的header和status写入到httpResponse中，body部分调用的是父类的模板方法。
必需的配置
添加HttpMessageConverter转换器配置
不添加会报错：
springboot no converter for [class org.springframework.core.io.inputstreamresource] with preset content-type '.....']报这个错误的原因大概就是我们在Controller层使用
@RestController注解，这个注解包含@ResponseBody注解，AbstractMessageConverterMethodProcessor类的子类RequestResponseBodyMethodProcessor是用来处理@Responsebody注解的，而HttpEntityMethodProcessor是AbstractMessageConverterMethodProcessor的另一个子类，该processor专门处理返回值类型是ResponseEntity类型的controller返回值。所以按照原理来说，不使用
@RestController和@Responsebody注解就可以不用添加这个HttpMessageConverter转换器配置，但是我这里不知道为啥即使不使用@RestController注解还是要必须添加这个转换器配置才行。有懂的老铁欢迎评论。@Configuration public class WebMVCConfig implements WebMvcConfigurer { public void configureMessageConverters(List<HttpMessageConverter<?>> converters) { ResourceHttpMessageConverter resHttpMessageConverter = new ResourceHttpMessageConverter(); final List<MediaType> list = new ArrayList<>(); list.add(MediaType.IMAGE_JPEG); list.add(MediaType.IMAGE_PNG); list.add(MediaType.APPLICATION_OCTET_STREAM); resHttpMessageConverter.setSupportedMediaTypes(list); converters.add(resHttpMessageConverter); } }使用到的实体和Mapper
import com.baomidou.mybatisplus.core.mapper.BaseMapper; import org.apache.ibatis.annotations.Mapper; @Mapper public interface FileMapper extends BaseMapper<ThirdFile> { }import com.alibaba.fastjson.annotation.JSONField; import com.baomidou.mybatisplus.annotation.IdType; import com.baomidou.mybatisplus.annotation.TableField; import com.baomidou.mybatisplus.annotation.TableId; import com.baomidou.mybatisplus.annotation.TableName; import lombok.Builder; import lombok.Data; @TableName("third_file") @Data @Builder public class ThirdFile { @TableId(value = "id",type = IdType.INPUT) private String id; @TableField("name") private String name; @TableField("size") private Long size; @TableField("version") private Integer version; @TableField("create_time") @JSONField(name = "create_time") private Long createTime; @TableField("update_time") @JSONField(name = "update_time") private Long updateTime; }
定义泛型接口
import org.springframework.http.HttpHeaders;
import org.springframework.http.ResponseEntity;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
public interface DownLoadFileService<T> {
ResponseEntity<T> downloadFile(String id);
default HttpHeaders getHttpHeaders(String filename) throws UnsupportedEncodingException {
HttpHeaders headers = new HttpHeaders();
headers.add(HttpHeaders.CONTENT_DISPOSITION, String.format("attachment; filename=\"%s\"", URLEncoder.encode(filename, StandardCharsets.UTF_8.name())));
headers.add(HttpHeaders.CACHE_CONTROL, "no-cache, no-store, must-revalidate");
headers.add(HttpHeaders.PRAGMA, "no-cache");
headers.add(HttpHeaders.EXPIRES, "0");
return headers;
}
}
具体实现
第一种:返回InputStreamResource
import lombok.SneakyThrows;
import lombok.extern.log4j.Log4j2;
import org.springframework.core.io.InputStreamResource;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import javax.servlet.ServletContext;
import java.io.InputStream;
@Log4j2
@Service
public class InputStreamResourceDownService implements DownLoadFileService<InputStreamResource> {
private final MinioTemplate minioTemplate;
private final FileMapper fileMapper;
private final ServletContext servletContext;
public InputStreamResourceDownService(MinioTemplate minioTemplate, FileMapper fileMapper, ServletContext servletContext) {
this.minioTemplate = minioTemplate;
this.fileMapper = fileMapper;
this.servletContext = servletContext;
}
@SneakyThrows
@Override
public ResponseEntity<InputStreamResource> downloadFile(String id) {
ThirdFile thirdFile = fileMapper.selectById(id);
InputStream inputStream = minioTemplate.get(thirdFile.getName());
InputStreamResource inputStreamResource = new InputStreamResource(inputStream);
String fileName = thirdFile.getName();
MediaType mediaType = MediaTypeUtils.getMediaTypeForFileName(this.servletContext, fileName);
log.info("fileName: " + fileName);
log.info("mediaType: " + mediaType);
return ResponseEntity
.ok()
.headers(getHttpHeaders(fileName))
.contentLength(thirdFile.getSize())
.contentType(mediaType)
.body(inputStreamResource);
}
}
第二种:返回Resource
import lombok.SneakyThrows;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
@Service
public class ResourceDownLoadService implements DownLoadFileService<Resource> {
private final MinioTemplate minioTemplate;
private final FileMapper fileMapper;
public ResourceDownLoadService(MinioTemplate minioTemplate, FileMapper fileMapper) {
this.minioTemplate = minioTemplate;
this.fileMapper = fileMapper;
}
@SneakyThrows
@Override
public ResponseEntity<Resource> downloadFile(String id) {
ThirdFile thirdFile = fileMapper.selectById(id);
InputStream inputStream = minioTemplate.get(thirdFile.getName());
// 读取 InputStream 的数据到字节数组中
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
byte[] fileBytes = outputStream.toByteArray();
return ResponseEntity.ok()
.headers(getHttpHeaders(thirdFile.getName()))
.contentLength(fileBytes.length)
.contentType(MediaType.APPLICATION_OCTET_STREAM)
.body(new ByteArrayResource(fileBytes));
}
}
第三种:返回StreamingResponseBody
import lombok.SneakyThrows;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import org.springframework.util.StreamUtils;
import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;
import java.io.IOException;
import java.io.InputStream;
@Service
public class StreamingResponseBodyDownLoadService implements DownLoadFileService<StreamingResponseBody> {
private final MinioTemplate minioTemplate;
private final FileMapper fileMapper;
public StreamingResponseBodyDownLoadService(MinioTemplate minioTemplate, FileMapper fileMapper) {
this.minioTemplate = minioTemplate;
this.fileMapper = fileMapper;
}
@SneakyThrows
@Override
public ResponseEntity<StreamingResponseBody> downloadFile(String id) {
ThirdFile thirdFile = fileMapper.selectById(id);
InputStream inputStream = minioTemplate.get(thirdFile.getName());
return ResponseEntity.ok()
.headers(getHttpHeaders(thirdFile.getName()))
.contentType(MediaType.APPLICATION_OCTET_STREAM)
.body(outputStream -> {
try (InputStream inputStream2 = inputStream) {
StreamUtils.copy(inputStream2, outputStream);
} catch (IOException ignored) {
}
});
}
}
第四种:返回HttpServletResponse输出流
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.InputStream;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
@Log4j2
@Service("srDownLoadFileService")
public class ServletResponseDownService implements DownLoadFileService {
private final MinioTemplate minioTemplate;
private final FileMapper fileMapper;
private final ServletContext servletContext;
private final HttpServletResponse response;
public ServletResponseDownService(MinioTemplate minioTemplate, FileMapper fileMapper, ServletContext servletContext, HttpServletResponse response) {
this.minioTemplate = minioTemplate;
this.fileMapper = fileMapper;
this.servletContext = servletContext;
this.response = response;
}
@SneakyThrows
@Override
public ResponseEntity downloadFile(String id) {
ThirdFile thirdFile = fileMapper.selectById(id);
InputStream inputStream = minioTemplate.get(thirdFile.getName());
String fileName = thirdFile.getName();
MediaType mediaType = MediaTypeUtils.getMediaTypeForFileName(this.servletContext, fileName);
log.info("fileName: " + fileName);
log.info("mediaType: " + mediaType);
// Content-Type, eg: application/pdf
response.setContentType(mediaType.getType());
// Content-Disposition
response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=" + URLEncoder.encode(fileName, StandardCharsets.UTF_8.name()));
// Content-Length
response.setContentLength(Math.toIntExact(thirdFile.getSize()));
BufferedInputStream inStream = new BufferedInputStream(inputStream);
BufferedOutputStream outStream = new BufferedOutputStream(response.getOutputStream());
byte[] buffer = new byte[1024];
int bytesRead = 0;
while ((bytesRead = inStream.read(buffer)) != -1) {
outStream.write(buffer, 0, bytesRead);
}
outStream.flush();
inStream.close();
return null;
}
}
Spring注入泛型接口使用
@Log4j2
@RestController
@RequestMapping("v1/api/file")
public class FileController {
// 泛型接口注入
private final DownLoadFileService<InputStreamResource> isrDownLoadFileService;
private final DownLoadFileService<Resource> rDownLoadFileService;
private final DownLoadFileService<StreamingResponseBody> srbDownLoadFileService;
private final DownLoadFileService srDownLoadFileService;
public FileController(DownLoadFileService<InputStreamResource> isrDownLoadFileService, DownLoadFileService<Resource> rDownLoadFileService, DownLoadFileService<StreamingResponseBody> srbDownLoadFileService, DownLoadFileService srDownLoadFileService) {
this.isrDownLoadFileService = isrDownLoadFileService;
this.rDownLoadFileService = rDownLoadFileService;
this.srbDownLoadFileService = srbDownLoadFileService;
this.srDownLoadFileService = srDownLoadFileService;
}
@RequestMapping(value = "/download1", method = RequestMethod.GET,produces = {MediaType.APPLICATION_OCTET_STREAM_VALUE})
@SneakyThrows
public ResponseEntity<InputStreamResource> downloadFile1(String id){
return isrDownLoadFileService.downloadFile(id);
}
@RequestMapping(value = "/download2", method = RequestMethod.GET, produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
@SneakyThrows
public ResponseEntity<Resource> downloadFile2(String id) {
return rDownLoadFileService.downloadFile(id);
}
@GetMapping(value = "/download3", produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
public ResponseEntity<StreamingResponseBody> downloadFile3(@RequestParam(name = "id") String id) {
return srbDownLoadFileService.downloadFile(id);
}
@GetMapping(value = "/download4")
public void downloadFile4(@RequestParam(name = "id") String id) {
srDownLoadFileService.downloadFile(id);
}
}
参考：
some ways for creating the file downloading function