备忘！！

获取文件源
Thread.currentThread().getContextClassLoader()  .getResource("").getFile();

• mongodb的删除GridFS文件

if(isUseGridFS){
    GridFS gridFiles = new GridFS(mongoTemplate.getDb());
    gridFiles.remove(new Query().addCriteria(where("filename").regex("^"+fileInfo.getFileId())).getQueryObject());
}else{
    mongoTemplate.remove(new Query().addCriteria(where("id").is(fileInfo.getFileId())), FileExt.class);
}

• 保存GridFS

    GridFS gfs = new GridFS(mongoTemplate.getDb());

    GridFSInputFile gfsFile = gfs.createFile(inputStream);
    gfsFile.setFilename(fileInfo.getFileId() + fileInfo.getExtension());
    gfsFile.setMetaData(new BasicDBObject("aliases", fileInfo.getFileName() + fileInfo.getExtension()));
    gfsFile.save();

• 查找文件

InputStream inputStream = null;
    if(fileInfo.getUseGridFS()){
        GridFS gfsPhoto = new GridFS(mongoTemplate.getDb());
        GridFSDBFile gridFSDBFile = gfsPhoto.findOne(fileInfo.getFileId() + fileInfo.getExtension());
        if(gridFSDBFile != null){
            inputStream = gridFSDBFile.getInputStream();
        } else {
            log.warn("文件不存在 ");
            response.sendError(HttpServletResponse.SC_NOT_FOUND, "文件不存在");
            return false;
        }
    }