今天需要将FTP某个文件夹下的图片做批量的展示，准备使用BASE64进行编码在前台直接显示
在使用ftpClient.listFiles()方法将所有的文件名取出后准备在循环中得到inputstream流，但是再操作中发现，一个图片正常显示，但是多个的话就只有第一个可以取到流，其他的均为空。试了网上的很多方法然并卵。
最后发现要将每一个循环都当做一个FTP通讯要将所有的IO，FTPClient均在循环中进行关闭
下边是涉事的代码

InputStream inputStream=null;
        BufferedInputStream bufferedInputStream=null;
        ByteArrayOutputStream byteArrayOutputStream=null;
        BufferedOutputStream bufferedOutputStream=null;
        List<Object> list=new ArrayList<Object>();
        Map<String, String> map=null;
        try {
            String diretory=FTPDIR+rightId;
            List<FTPFile> ftpFiles=fileCenFTPService.achieveFolderListByDir(diretory);
            String fileName=null;
            if(ftpFiles!=null && ftpFiles.size()>0){
                for(int i=0;i<ftpFiles.size();i++){
                    FTPFile ftpFile = ftpFiles.get(i);
                    map=new HashMap<String, String>();
                    fileName = ftpFile.getName();
                    inputStream=fileCenFTPService.fileInputStreamDownload(diretory+"/"+fileName);
                    bufferedInputStream = new BufferedInputStream(inputStream);
                    byteArrayOutputStream =new ByteArrayOutputStream();
                    bufferedOutputStream = new BufferedOutputStream(byteArrayOutputStream);
                    byte[] buffer=new byte[1024];
                    int len=bufferedInputStream.read(buffer);
                    while(len!=-1){
                        bufferedOutputStream.write(buffer, 0, len);
                        len=bufferedInputStream.read(buffer);
                    }
                    bufferedOutputStream.flush();
                    byte[] bytes=byteArrayOutputStream.toByteArray();
                    BASE64Encoder encoder = new BASE64Encoder();
                    String base64String=encoder.encode(bytes).trim();
                    map.put("fileName", fileName);
                    map.put("content", base64String);
                    list.add(map);
                    bufferedOutputStream.close();
                    byteArrayOutputStream.close();
                    inputStream.close();
                    fileCenFTPService.disconnect();
                    
                }

里边主要的两个方法是封装好的

@Override
    public List<FTPFile> achieveFolderListByDir(String directory) throws IOException {
        try {
            FTPClient ftpClient = achieveFTPClient();
            ftpClient.setControlEncoding("GBK");//设置编码,否则中文名是乱码
//          System.out.println(directory);
//          if(!ftpClient.changeWorkingDirectory(directory)){
//              ftpClient.makeDirectory(directory);
//          }
            
            //解决中文路径的问题
            if(ftpClient.changeWorkingDirectory(new String(directory.getBytes("GBK"),"ISO-8859-1"))) {
                
                FTPFile[] ftpFileArr = ftpClient.listFiles();
//              System.out.println(ftpFileArr.length);
                List<FTPFile> folderList = new ArrayList<FTPFile>();
                for(FTPFile file : ftpFileArr){
//                  System.out.println(file.getName());
                    folderList.add(file);
                }
                return folderList;
            } else {
                return null;
            }
            
        } catch (Exception er) {
            throw new IOException("获取文件列表失败 : " + er.getMessage());
        } finally {
            disconnect();
        }
    }
@Override
    public InputStream fileInputStreamDownload(String remoteName) throws IOException {
        InputStream is = null;
        try {
            FTPClient ftpClient = achieveFTPClient();
            is = ftpClient.retrieveFileStream(new String(remoteName.getBytes("GBK"),"ISO-8859-1"));
        } catch (IOException er) {
            throw new IOException("下载文件流失败 : " + er.getMessage());
        }
        return is;
    }

public void disconnect() throws IOException {  
        try {  
            FTPClient ftpClient = achieveFTPClient(); 
            if (ftpClient.isConnected()) {  
                ftpClient.disconnect();  
                ftpClient = null;  
            }  
        } catch (IOException e) {  
            throw new IOException("Could not disconnect from server.", e);  
        }  
    }