SpringBoot+fileUpload获取文件上传进度

时间:2021-12-10 00:10:06

我本人在网上找了很多关于文件上传进度获取的文章,普遍基于spring mvc 框架通过 fileupload 实现,对于spring boot 通过 fileupload 实现的帖子非常少,由于小弟学艺不精,虽然 spring boot 和 spring mvc 相差不大,只是配置方式的差别,还是搞了很久,上传此文章的目的是希望自己作为文本保留,以便日后查看备忘,并且希望通过我的例子可以帮助到其他人而已,如果各位大佬发现小弟对于某些知识有误解,还请不吝赐教,先谢谢各位前辈了!

写此篇文章之前我查了很多关于spring mvc 框架通过 fileupload 实现进度条的帖子和文章,在此对各位作者表示感谢!

本功能基于commons fileupload 组件实现

1.首先,不能在程序中直接使用 fileupload.parserequest(request)的方式来获取 request 请求中的 multipartfile 文件对象,原因是因为在 spring 默认的文件上传处理器 multipartresolver 指向的类commonsmultipartresolver 中就是通过 commons fileupload 组件实现的文件获取,因此,在代码中再次使用该方法,是获取不到文件对象的,因为此时的 request 对象是不包含文件的,它已经被commonsmultipartresolver 类解析处理并转型。

commonsmultipartresolver 类中相关源码片段:

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protected multipartparsingresult parserequest(httpservletrequest request) throws multipartexception {
    string encoding = determineencoding(request);
    fileupload fileupload = preparefileupload(encoding);
    try {
      list<fileitem> fileitems = ((servletfileupload) fileupload).parserequest(request);
      return parsefileitems(fileitems, encoding);
    }
    catch (fileuploadbase.sizelimitexceededexception ex) {
      throw new maxuploadsizeexceededexception(fileupload.getsizemax(), ex);
    }
    catch (fileuploadbase.filesizelimitexceededexception ex) {
      throw new maxuploadsizeexceededexception(fileupload.getfilesizemax(), ex);
    }
    catch (fileuploadexception ex) {
      throw new multipartexception("failed to parse multipart servlet request", ex);
    }
}

2.由于spring 中的 commonsmultipartresolver 类中并没有加入 processlistener 文件上传进度监听器,所以,直接使用 commonsmultipartresolver 类是无法监听文件上传进度的,如果我们需要获取文件上传进度,就需要继承 commonsmultipartresolver 类并重写 parserequest 方法,在此之前,我们需要创建一个实现了 processlistener 接口的实现类用于监听文件上传进度。

processlistener接口实现类:

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import javax.servlet.http.httpsession;
import org.apache.commons.fileupload.progresslistener;
import org.springframework.stereotype.component;
 
@component
public class uploadprogresslistener implements progresslistener{
 
  private httpsession session;
 
  public void setsession(httpsession session){
    this.session=session;
    progressentity status = new progressentity();
    session.setattribute("status", status);
  }
 
  /*
   * pbytesread 到目前为止读取文件的比特数 pcontentlength 文件总大小 pitems 目前正在读取第几个文件
   */
  @override
  public void update(long pbytesread, long pcontentlength, int pitems) {
    progressentity status = (progressentity) session.getattribute("status");
    status.setpbytesread(pbytesread);
    status.setpcontentlength(pcontentlength);
    status.setpitems(pitems);
  }
}

progressentity 实体类:

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import org.springframework.stereotype.component;
 
@component
public class progressentity {
  private long pbytesread = 0l;  //到目前为止读取文件的比特数 
  private long pcontentlength = 0l;  //文件总大小 
  private int pitems;        //目前正在读取第几个文件
 
  public long getpbytesread() {
    return pbytesread;
  }
  public void setpbytesread(long pbytesread) {
    this.pbytesread = pbytesread;
  }
  public long getpcontentlength() {
    return pcontentlength;
  }
  public void setpcontentlength(long pcontentlength) {
    this.pcontentlength = pcontentlength;
  }
  public int getpitems() {
    return pitems;
  }
  public void setpitems(int pitems) {
    this.pitems = pitems;
  }
  @override
  public string tostring() {
    float tmp = (float)pbytesread;
    float result = tmp/pcontentlength*100;
    return "progressentity [pbytesread=" + pbytesread + ", pcontentlength="
        + pcontentlength + ", percentage=" + result + "% , pitems=" + pitems + "]";
  }
}

最后,是继承 commonsmultipartresolver 类的自定义文件上传处理类:

 

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import java.util.list;
import javax.servlet.http.httpservletrequest;
import org.apache.commons.fileupload.fileitem;
import org.apache.commons.fileupload.fileupload;
import org.apache.commons.fileupload.fileuploadbase;
import org.apache.commons.fileupload.fileuploadexception;
import org.apache.commons.fileupload.servlet.servletfileupload;
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.web.multipart.maxuploadsizeexceededexception;
import org.springframework.web.multipart.multipartexception;
import org.springframework.web.multipart.commons.commonsmultipartresolver;
 
public class custommultipartresolver extends commonsmultipartresolver{
 
  @autowired
  private uploadprogresslistener uploadprogresslistener;
 
  @override
  protected multipartparsingresult parserequest(httpservletrequest request) throws multipartexception {
    string encoding = determineencoding(request);
    fileupload fileupload = preparefileupload(encoding);
    uploadprogresslistener.setsession(request.getsession());//问文件上传进度监听器设置session用于存储上传进度
    fileupload.setprogresslistener(uploadprogresslistener);//将文件上传进度监听器加入到 fileupload 中
    try {
      list<fileitem> fileitems = ((servletfileupload) fileupload).parserequest(request);
      return parsefileitems(fileitems, encoding);
    }
    catch (fileuploadbase.sizelimitexceededexception ex) {
      throw new maxuploadsizeexceededexception(fileupload.getsizemax(), ex);
    }
    catch (fileuploadbase.filesizelimitexceededexception ex) {
      throw new maxuploadsizeexceededexception(fileupload.getfilesizemax(), ex);
    }
    catch (fileuploadexception ex) {
      throw new multipartexception("failed to parse multipart servlet request", ex);
    }
  }
 
}

3.此时,所有需要的类已经准备好,接下来我们需要将 spring 默认的文件上传处理类取消自动配置,并将 multipartresolver 指向我们刚刚创建好的继承 commonsmultipartresolver 类的自定义文件上传处理类。

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import org.springframework.boot.springapplication;
import org.springframework.boot.autoconfigure.enableautoconfiguration;
import org.springframework.boot.autoconfigure.web.multipartautoconfiguration;
import org.springframework.boot.web.servlet.servletcomponentscan;
import org.springframework.context.annotation.bean;
import org.springframework.context.annotation.componentscan;
import org.springframework.context.annotation.configuration;
import org.springframework.web.multipart.multipartresolver;
 
import com.example.listener.custommultipartresolver;
 
/*
 * 将 spring 默认的文件上传处理类取消自动配置,这一步很重要,没有这一步,当multipartresolver重新指向了我们定义好
 * 的新的文件上传处理类后,前台传回的 file 文件在后台获取会是空,加上这句话就好了,推测不加这句话,spring 依然
 * 会先走默认的文件处理流程并修改request对象,再执行我们定义的文件处理类。(这只是个人推测)
 * exclude表示自动配置时不包括multipart配置
 */
@enableautoconfiguration(exclude = {multipartautoconfiguration.class})
 
@configuration
@componentscan(basepackages = {"com.example"})
@servletcomponentscan(basepackages = {"com.example"})
public class uploadprogressapplication {
 
/*
 * 将 multipartresolver 指向我们刚刚创建好的继承 commonsmultipartresolver 类的自定义文件上传处理类
 */
@bean(name = "multipartresolver")
public multipartresolver multipartresolver() {
  custommultipartresolver custommultipartresolver = new custommultipartresolver();
  return custommultipartresolver;
}
 
public static void main(string[] args) {
  springapplication.run(uploadprogressapplication.class, args);
}
}

至此,准备工作完成,我们再创建一个测试用的 controller 和 html 页面用于文件上传。

controller:

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import org.springframework.stereotype.controller;
import org.springframework.web.bind.annotation.requestmapping;
import org.springframework.web.bind.annotation.requestmethod;
import org.springframework.web.bind.annotation.responsebody;
import org.springframework.web.multipart.multipartfile;
import org.springframework.web.servlet.modelandview;
 
@controller
@requestmapping("/uploadprogress")
public class uploadcontroller {
 
  @requestmapping(value = "/showupload", method = requestmethod.get)
  public modelandview showupload() {
    return new modelandview("/uploadprogressdemo");
  }
 
  @requestmapping("/upload")
  @responsebody
  public void uploadfile(multipartfile file) {
    system.out.println(file.getoriginalfilename());
  }
 
}

html:

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<!doctype html>
<html>
<head>
  <meta charset="utf-8"></meta>
  <title>测试</title>这里写代码片
</head>
<body>
  这是文件上传页面
  <form action="/uploadprogress/upload" method="post" enctype="multipart/form-data">
    <input type="file" name="file"/>
    <br/>
    <input type="submit" value="提交"/>
  </form>
</body>
</html>

经本人测试,确实可以获取文件上传进度,前台页面修改进度条进度可以采用前台页面轮询的方式访问后台,在相应action中通过存储在session中的对象 status 来获取最新的上传进度并返回展示即可。

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:https://blog.csdn.net/qq_27607579/article/details/77914958