springboot上传文件显示上传进度[通俗易懂]

		<dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.2.2</version>
        </dependency>

@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
public class ProgressEntity { 
   


    /** * 读取的文件的比特数 */
    private long bytesRead = 0L;

    /** * 文件的总大小 */
    private long contentLength = 0L;

    /** * 目前正在读取第几个文件 */
    private int items;

    /** * 开始上传时间，用于计算上传速率 */
    private long startTime = System.currentTimeMillis();

}

/** * * @author Administrator * * 要获得上传文件的实时详细信息，必须继承org.apache.commons.fileupload.ProgressListener类， * 获得信息的时候将进度条对象Progress放在该监听器的session对象中 */
@Component
public class FileUploadProgressListener implements ProgressListener { 
   

    private HttpSession session;

    public void setSession(HttpSession session){ 
   
        this.session=session;
        //保存上传状态
        ProgressEntity progressEntity = new ProgressEntity();
        session.setAttribute("progressEntity", progressEntity);
    }

    @Override
    public void update(long bytesRead, long contentLength, int items) { 
   
        ProgressEntity progressEntity = (ProgressEntity) session.getAttribute("progressEntity");
        //已读取数据长度
        progressEntity.setBytesRead(bytesRead);
        //文件总长度
        progressEntity.setContentLength(contentLength);
        //正在保存第几个文件
        progressEntity.setItems(items);
    }
}

/** * @author Administrator * * SpringMVC默认有一个文件解析器CommonsMultipartResolver用来解析上传的文件，我们需要重写该类， * 自己重写的监听器放到org.apache.commons.fileupload.FileUpload中，还需要将session放到自定义的监听器中 */

public class CustomMultipartResolver extends CommonsMultipartResolver { 
   

    /** * 注入第二步写的FileUploadProgressListener * 此处一定要检查是否注入成功了，不成功的话会报错 */
    @Autowired
    private FileUploadProgressListener progressListener;

    public void setProgressListener(FileUploadProgressListener progressListener) { 
   
        this.progressListener = progressListener;
    }

    @Override
    public MultipartParsingResult parseRequest(HttpServletRequest request) throws MultipartException { 
   
        String encoding = determineEncoding(request);
        FileUpload fileUpload = prepareFileUpload(encoding);
        progressListener.setSession(request.getSession());
        fileUpload.setProgressListener(progressListener);
        try { 
   
            List<FileItem> fileItems = ((ServletFileUpload) fileUpload).parseRequest(request);
            return parseFileItems(fileItems, encoding);
        } catch (FileUploadBase.SizeLimitExceededException ex) { 
   
            throw new MaxUploadSizeExceededException(fileUpload.getSizeMax(), ex);
        } catch (FileUploadException ex) { 
   
            throw new MultipartException("Could not parse multipart servlet request", ex);
        }
    }

}

@Configuration
public class CorsConfig implements WebMvcConfigurer { 
   

    /** * 指定自定义解析器 * 将 multipartResolver 指向我们刚刚创建好的继承 CustomMultipartResolver 类的 自定义文件上传处理类 * * @return */
    @Bean(name = "multipartResolver")
    public MultipartResolver multipartResolver() { 
   
        return new CustomMultipartResolver();
    }
}

 /** * 获取上传进度 * * @return */
    @GetMapping(value = "/uploadStatus")
    @ApiOperation("获取上传进度")
    public Object uploadStatus() { 
   
        HttpServletRequest request = HttpContextUtils.getHttpServletRequest();
        HttpSession session = request.getSession();
        ProgressEntity percent = (ProgressEntity) session.getAttribute("progressEntity");
       // System.out.println("^^^^"+percent.toString());
      //当前时间
        long nowTime = System.currentTimeMillis();
        //已传输的时间
        long time = (nowTime - percent.getStartTime())/1000+1;
        //传输速度 ;单位：byte/秒
        double velocity =((double) percent.getBytesRead())/(double)time;
        //估计总时间
        double totalTime = percent.getContentLength()/velocity;
        //估计剩余时间
        double timeLeft = totalTime - time;
        //已经完成的百分比
        int percent1 = (int)(100 * (double) percent.getBytesRead() / (double) percent.getContentLength());
        //已经完成数单位:m
        double length = ((double) percent.getBytesRead())/1024/1024;
        //总长度 M
        double totalLength = (double) percent.getContentLength()/1024/1024;
        StringBuffer sb = new StringBuffer();
        //拼接上传信息传递到jsp中
        sb.append(percent+":"+length+":"+totalLength+":"+velocity+":"+time+":"+totalTime+":"+timeLeft+":"+percent.getItems());
        System.out.println("百分比====>"+percent1);
        System.out.println("已传输时间====>"+time+"------剩余时间--->"+timeLeft+"======已经完成===="+length);
        return null;
    }