Java实现批量下载选中文件功能

 private list<string> downloadpaths = new arraylist<string>();//存储选中文件的下载地址 
 private outputstream res; 
 private zipoutputstream zos; 
 private string outpath; 
 private string lessionidstr;// 选中文件id拼接的字符串 
 private string filename; //浏览器下载弹出框中显示的文件名 

/** 
   * 下载多个文件：压缩成zip 
   * 
   * @return 
   * @throws exception 
   */ 
  public string downloadlessionszip() { 
    downloadpaths.clear(); 
    string firstfilename = "";// 第一个文件的文件名 
    list<downloadfilevo> filevos = new linkedlist<downloadfilevo>(); 
    if (stringutils.isnotempty(lessionidstr)) { 
      int end = lessionidstr.lastindexof(","); 
      if (end > 0) { 
        if (end == lessionidstr.length() - 1) { 
          lessionidstr = lessionidstr.substring(0, end); 
        } 
        string[] ids = lessionidstr.split(","); 
        for (int i = 0; i < ids.length; i++) { 
          if (stringutils.isnumeric(ids[i])) { 
            bkpersonlession lession = bkpersonlessionservice.downloadlession(integer.parseint(ids[i])); 
            if (lession != null) { 
              filevos.add(new downloadfilevo(lession 
                  .getlessionname(), getcontextrealpath() 
                  + lession.getlessionsavepath())); 
              downloadpaths.add(getcontextrealpath() 
                  + lession.getlessionsavepath()); 
            } 
            if (i == 0) {               
                       firstfilename = lession.getlessionname(); 
            } 
          } 
        } 
      } 
    } 
    // 有数据可以下载 
    if (downloadpaths.size() != 0) { 
      // 进行预处理 
      preprocess(firstfilename); 
    } else { 
      // 没有文件可以下载，返回nodata 
      return "nodata"; 
    } 
    // 处理 
    writezip(filevos); 
    // 后处理关闭流 
    afterprocess(); 
    return null; 
  } 
  // 压缩处理 
  public void writezip(list<downloadfilevo> filevos) { 
    byte[] buf = new byte[8192]; 
    int len; 
    for (downloadfilevo filevo : filevos) { 
      file file = new file(filevo.getfilesavepath()); 
      if (!file.isfile()) 
        continue; 
      zipentry ze = new zipentry(filevo.getfilename() 
          + filevo.getfilesavepath().substring( 
              filevo.getfilesavepath().lastindexof(".")));                           
      try { 
        zos.putnextentry(ze); 
        bufferedinputstream bis = new bufferedinputstream( 
            new fileinputstream(file)); 
        while ((len = bis.read(buf)) > 0) { 
          zos.write(buf, 0, len); 
        } 
        bis.close(); 
        zos.closeentry(); 
      } catch (ioexception e) { 
        e.printstacktrace(); 
      } 
    } 
  } 
  // 预处理 
  public void preprocess(string firsefilename) { 
    string zipname = "【批量下载】" + firsefilename + "等.zip"; 
    string filename = ""; 
    try { 
      filename = new string(zipname.getbytes("gbk"), "8859_1"); 
    } catch (unsupportedencodingexception e1) { 
      e1.printstacktrace(); 
    } 
    this.filename = filename; 
    httpservletresponse response = servletactioncontext.getresponse(); 
    try { 
      res = response.getoutputstream(); 
      // 清空输出流(在迅雷下载不会出现一长窜) 
      response.reset(); 
      // 设定输出文件头 
      response.setheader("content-disposition", "attachment;filename=" 
          + filename); 
      response.setcontenttype("application/zip"); 
      zos = new zipoutputstream(res); 
    } catch (ioexception e) { 
      e.printstacktrace(); 
    } 
  } 
  // 后处理 
  public void afterprocess() { 
    try { 
      if (zos != null) { 
        zos.close(); 
      } 
      if (res != null) { 
        res.close(); 
      } 
    } catch (ioexception e) { 
      e.printstacktrace(); 
    } 
  } 

<action name="downloadbkpersonlessionszip" class="bkpersonlessionaction"  
      method="downloadlessionszip">//class值为bean.xml中配置的bean 
  <result name="nodata" type="httpheader"> 
    <param name="status">204</param>//表示响应执行成功，但没有数据返回，浏览器不用刷新，不用导向新页面 
  </result> 
</action>