【springboot】实现文件上传和下载

news2025/1/4 17:21:02

1. 新建一个springboot项目

新建一个springboot项目，选择web，默认即可.

主要pom配置文件如下：

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.10.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!--web包-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
<!--    maven打包设置-->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <includeSystemScope>true</includeSystemScope>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

2. 配置文件

在配置文件中配置文件上传和下载的根目录，文件大小限制等。

application.properties

file.upload.url=path/to/upload
# 文件大小限制
spring.servlet.multipart.max-file-size=10MB 
# 请求大小限制
spring.servlet.multipart.max-request-size=20MB

application.yml

file.upload.url: path/to/upload
spring:
  servlet:
    multipart:
      # 文件大小限制
      max-file-size: 10MB
      
      max-request-size: 20MB

3. 控制类实现文件上传和下载

在控制类中实现文件上传和下载。其中，文件上传通过MultipartFile实现文件类型限制、文件大小限制、多文件上传等，下载通过文件流实现。

@RestController
@RequestMapping(value = "/file")
@CrossOrigin // 允许跨域
@ControllerAdvice // 全局异常处理
public class FileController {

    //上传的根目录
    @Value("${file.upload.url}")
    private String uploadFilePath;
    @Value("${file.upload.url}")
    private String downloadFilePath;

    //捕获上传文件过大的异常
    //@ExceptionHandler标识方法将处理指定类型的异常
    @ExceptionHandler(MaxUploadSizeExceededException.class)
    public ResponseEntity<String> handleMaxSizeException(MaxUploadSizeExceededException exc) {
        return ResponseEntity.status(HttpStatus.PAYLOAD_TOO_LARGE).body("文件过大，请重新选择上传图片！");
    }
    
    @RequestMapping("/upload")
    public String httpUpload(
            @RequestParam("files")
                     //MultipartFile 是 Spring 框架中用于处理文件上传的接口
                     MultipartFile files[]) {
        StringBuffer urls = new StringBuffer();
        //遍历多个文件
        for (int i = 0; i < files.length; i++) {
            //获取文件类型
            String contentType = files[i].getContentType();
            System.out.println(contentType);
            if (!contentType.contains("image")) {
                return "文件格式不正确，请重新选择图片！";
            }
            //获取上传文件的后缀名
            String postfix = files[i].getOriginalFilename().substring(files[i].getOriginalFilename().lastIndexOf("."));
            //生成文件名 使用时间戳，避免重名
            String fileName = System.currentTimeMillis()+postfix;
            System.out.println(fileName);
//            File dest = new File(uploadFilePath + '/' + fileName);
            File dest = new File(uploadFilePath + '/' + fileName);
            //目录不存在则创建目录
            if (!dest.getParentFile().exists()) {
                dest.getParentFile().mkdirs();
            }
            try {
                //将上传的文件保存到指定的目标位置
                files[i].transferTo(dest);
            } catch (Exception e) {
                return "程序错误，请重新上传\n" + e.toString();
            }
            urls.append("\n"+uploadFilePath + '\\' + fileName);
        }
        return "文件上传成功" + urls.toString();
    }

    @RequestMapping("/download")
    public String fileDownLoad(HttpServletResponse response, @RequestParam("fileName") String fileName) {
//        File file = new File(downloadFilePath + '/' + fileName);
        File file = new File(downloadFilePath + '\\' + fileName);
        if (!file.exists()) {
            return "下载文件不存在";
        }
        //清除之前设置的内容
        response.reset();
        //设置响应内容类型为二进制流
        response.setContentType("application/octet-stream");
        //设置响应字符编码为UTF-8
        response.setCharacterEncoding("utf-8");
        //设置响应文件大小
        response.setContentLength((int) file.length());
        //设置浏览器以附件的形式下载，并设置文件名
        response.setHeader("Content-Disposition", "attachment;filename=" + fileName);
        try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));) {
            byte[] buff = new byte[1024];
            OutputStream os = response.getOutputStream();
            int i = 0;
            while ((i = bis.read(buff)) != -1) {
                os.write(buff, 0, i);
                os.flush();
            }
        } catch (IOException e) {
            return "下载失败";
        }
        return "下载成功";
    }
}