使用 StreamProvider 将 Html 加载到 Excel

在加载包含外部资源的html时，我们经常面临以下两个问题：

1. 加载html流时，无法通过相对路径获取html文件引用的图片和外部资源。
2. 需要映射html文件中引用的外部资源路径。

这篇文章解释了如何实现IStreamProvider用于设置的界面HtmlLoadOptions.StreamProvider财产。通过实现这个接口，你将能够在加载Html流时加载外部资源或者这些外部资源是相对的。

这是显示用法的主要代码HtmlLoadOptions.StreamProvider

	class HtmlAttachedStreamProvider implements IStreamProvider
{
    static boolean IsHRef(String picPath)
    {
        //This handles http://,https:// file:// and probably ftp://.
        if (picPath.startsWith("http://")
            || picPath.startsWith("https://")
            || picPath.startsWith("file://")
            || picPath.startsWith("ftp://"))
        {
            return true;
        }
        return false;
    }
    static InputStream GetInputStream(String fileName)
    {
    	java.io.File f = new java.io.File(fileName);
        if(!f.exists() || !f.isFile())
        {
            return null;
        }
        FileInputStream fis = null;
        try
        {
           return fis = new FileInputStream(f);
        }catch(Exception e)
        {
        	return null;
        }
    }
    public void initStream(StreamProviderOptions options)
    {
    	try
    	{ 
    		
    		String absolutePath = null;
    		String oldPath = options.getDefaultPath();
    		if(oldPath.equals("/Files/Image1.png"))
        		 { 
                absolutePath = "G1.png";
        		 }
    		else if(oldPath.equals("/Files/image2.png"))
                absolutePath = "E1.png";
            else if(oldPath.equals(https://www.aspose.com/templates/aspose/img/products/cells/aspose_cells-for-net.svg"))
                absolutePath = "F1.png";
             

       
        if(absolutePath == null)
        {
            if(IsHRef(options.getDefaultPath()))
            {
               //get stream from path.
            }
            else 
            {
                options.setInputStream(GetInputStream(options.getDefaultPath()));
            }
            return;
        }
        options.setInputStream(GetInputStream(absolutePath));
    		
    	}catch(Exception e)
    	{
    		
    	}
      

    }

    public void closeStream(StreamProviderOptions options)
    {
    	try
    	{
    		 if(options.getStream() != null)
    	        {

    	            options.getStream().close();
    	        }
    	}catch(Exception e)
    	{
    		
    	}
       

    }
}
	public static void main(String[] args)throws Exception{
		
		// For complete examples and data files, please go to https://github.com/aspose-cells/Aspose.Cells-for-.NET
		  HtmlAttachedStreamProvider attachedStreamProvider = new HtmlAttachedStreamProvider();
          HtmlLoadOptions options = new HtmlLoadOptions();
          options.setStreamProvider(attachedStreamProvider);
          Workbook workbook = new Workbook( "html1.html", options);

          workbook.save("book1.xlsx");
		
	}