使用WorkbookSetting.StreamProvider控制外部资源

可能的使用场景

有时，您的Excel文件包含外部资源，例如链接的图像等。Aspose.Cells允许您使用Workbook.Settings.StreamProvider控制这些外部资源，该方法接受IStreamProvider接口的实现。每当您尝试呈现包含外部资源的工作表时，将调用IStreamProvider接口的方法，这将使您能够针对外部资源采取适当的操作。

使用WorkbookSetting.StreamProvider控制外部资源

以下示例代码解释了如何使用Workbook.Settings.StreamProvider。它加载包含链接图像的样本Excel文件。代码将链接图像替换为Aspose Logo，并使用SheetRender类将整个工作表呈现为单个图像。以下屏幕截图显示了示例Excel文件及其渲染输出图像供参考。正如您所见，损坏的链接图像已替换为Aspose Logo。

示例代码

// For complete examples and data files, please go to https://github.com/aspose-cells/Aspose.Cells-for-Java
//Implementation of IStreamProvider
class SP implements IStreamProvider
{
	public void closeStream(StreamProviderOptions arg0) throws Exception {
	}

	public void initStream(StreamProviderOptions options) throws Exception {

		//Open the filestream of Aspose Logo and assign it to StreamProviderOptions.Stream property
		File imgFile = new File(srcDir + "sampleControlExternalResourcesUsingWorkbookSetting_StreamProvider.png");

		byte[] bts = new byte[(int) imgFile.length()];

		FileInputStream fin = new FileInputStream(imgFile);
		fin.read(bts);
		fin.close();

		ByteArrayOutputStream baout = new ByteArrayOutputStream();
		baout.write(bts);
		baout.close();
		
		options.setStream(baout);
	}
}


public void Run() throws Exception {
	System.out.println("Aspose.Cells for Java Version: " + CellsHelper.getVersion());

	//String srcDir = Utils.Get_SourceDirectory();
	//String outDir = Utils.Get_OutputDirectory();

	//Load sample Excel file containing the external resource e.g. linked image etc.
	Workbook wb = new Workbook(srcDir + "sampleControlExternalResourcesUsingWorkbookSetting_StreamProvider.xlsx");

	//Provide your implementation of IStreamProvider
	wb.getSettings().setStreamProvider(new SP());

	//Access first worksheet
	Worksheet ws = wb.getWorksheets().get(0);

	//Specify image or print options, we need one page per sheet and png output
	ImageOrPrintOptions opts = new ImageOrPrintOptions();
	opts.setOnePagePerSheet(true);
	opts.setImageType(ImageType.PNG);

	//Create sheet render by passing required parameters
	SheetRender sr = new SheetRender(ws, opts);

	//Convert your entire worksheet into png image
	sr.toImage(0, outDir + "outputControlExternalResourcesUsingWorkbookSettingStreamProvider.png");

	// Print the message
	System.out.println("ControlExternalResourcesUsingWorkbookSetting_StreamProvider executed successfully.");
}

public static void main(String[] args) throws Exception {
	new ControlExternalResourcesUsingWorkbookSetting_StreamProvider().Run();
}