springboot文件下载

Spring Boot中文件下载可以通过以下步骤实现：

1. 通过Spring MVC配置一个处理器映射器和处理器适配器，处理文件下载请求。

@Configuration
@EnableWebMvc
public class MvcConfig implements WebMvcConfigurer {

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/files/**")
                .addResourceLocations("~/files/");
    }

    @Bean
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/");
        resolver.setSuffix(".html");
        return resolver;
    }

    @Bean
    public MappingJackson2HttpMessageConverter jsonConverter() {
        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        converter.setObjectMapper(new ObjectMapper().disable(SerializationFeature.FAIL_ON_EMPTY_BEANS));
        converter.setSupportedMediaTypes(MediaType.APPLICATION_JSON);
        return converter;
    }

    @Bean
    public HttpMessageConverters messageConverters() {
        return new HttpMessageConverters(jsonConverter());
    }

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedMethods("*")
                .allowedHeaders("*")
                .allowedOrigins("*");
    }
}

2. 创建一个Controller类，并为文件下载请求提供一个映射路径。

@RestController
public class FileDownloadController {

    private final static String BASE_PATH = "/files";
    private final static String DEFAULT_FILE_NAME = "example.txt";

    @GetMapping(BASE_PATH + "/{fileName:.+}")
    public void downloadFile(@PathVariable String fileName, HttpServletRequest request, HttpServletResponse response) throws IOException {

        String realPath = request.getServletContext().getRealPath("../" + BASE_PATH + "/" + fileName);

        File file = new File(realPath);

        if (!file.exists()) {
            response.sendError(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        String mimeType = request.getServletContext().getMimeType(file.getAbsolutePath());

        if (mimeType == null) {
            mimeType = "application/octet-stream";
        }

        response.setContentType(mimeType);
        response.setHeader("Content-Disposition", "attachment; filename=\"" + file.getName() + "\"");
        response.setContentLength((int) file.length());

        InputStream inputStream = new BufferedInputStream(new FileInputStream(file));

        FileCopyUtils.copy(inputStream, response.getOutputStream());
    }

    @GetMapping(BASE_PATH)
    public ResponseEntity<Resource> downloadDefaultFile(HttpServletRequest request) throws IOException {

        String realPath = request.getServletContext().getRealPath("../" + BASE_PATH + "/" + DEFAULT_FILE_NAME);

        Path path = Paths.get(realPath);
        Resource resource = new UrlResource(path.toUri());

        HttpHeaders headers = new HttpHeaders();
        headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + DEFAULT_FILE_NAME);

        return ResponseEntity.ok().headers(headers).contentLength(resource.contentLength()).contentType(MediaType.APPLICATION_OCTET_STREAM).body(resource);
    }
}

3. 启动Spring Boot应用程序并测试文件下载功能。使用浏览器或命令行工具尝试下载文件。