PdfStamper.CreateSignature和空的MemoryStream

Question

使用iTextSharp 5.3.4.0，我很難與PdfStamper和MemoryStream一起工作。

MemoryStream始終爲空。

PdfReader pdfReader = new PdfReader(Server.MapPath(@"Document.pdf")); 

    MemoryStream memoryStream = new MemoryStream(); 

    PdfStamper pdfStamper = PdfStamper.CreateSignature(pdfReader, memoryStream, '\0'); 

    //... 

    pdfStamper.Writer.CloseStream = false; 
    pdfStamper.Close(); 

    byte[] bt = memoryStream.GetBuffer(); //.ToArray() 
    pdfReader.Close(); 

Download Project (full source code)

我怎樣才能解決這個問題？謝謝！

Answer 1

在Default.aspx.cs你做相關的事情，你在你的問題的代碼塊冷落：

PdfStamper pdfStamper = PdfStamper.CreateSignature(pdfReader, memoryStream, '\0'); 

PdfSignatureAppearance pdfSignatureAppearance = pdfStamper.SignatureAppearance; 
//... 
pdfSignatureAppearance.PreClose(exc); 
//... 

pdfStamper.Writer.CloseStream = false; 
pdfStamper.Close(); 

每當你叫PdfSignatureAppearance.PreClose,還必須使用PdfSignatureAppearance.Close,不PdfStamper.Close,比照該方法單證：

/** 
* This is the first method to be called when using external signatures. The general sequence is: 
* preClose(), getDocumentBytes() and close(). 
* <p> 
* If calling preClose() <B>dont't</B> call PdfStamper.close(). 
* <p> 
* <CODE>exclusionSizes</CODE> must contain at least 
* the <CODE>PdfName.CONTENTS</CODE> key with the size that it will take in the 
* document. Note that due to the hex string coding this size should be 
* byte_size*2+2. 
* @param exclusionSizes a <CODE>HashMap</CODE> with names and sizes to be excluded in the signature 
* calculation. The key is a <CODE>PdfName</CODE> and the value an 
* <CODE>Integer</CODE>. At least the <CODE>PdfName.CONTENTS</CODE> must be present 
* @throws IOException on error 
* @throws DocumentException on error 
*/ 
public void PreClose(Dictionary<PdfName, int> exclusionSizes) { 

（從PdfSignatureAppearance.cs）

/** 
* Closes the document. No more content can be written after the 
* document is closed. 
* <p> 
* If closing a signed document with an external signature the closing must be done 
* in the <CODE>PdfSignatureAppearance</CODE> instance. 
* @throws DocumentException on error 
* @throws IOException on error 
*/ 
public void Close() { 

（從PdfStamper.cs）

原因是，當您使用CreateSignature(pdfReader, memoryStream, '\0'),創建PdfStamper時，壓模本身不會寫入內存流，而是寫入內部ByteBuffer（這是最終簽名創建和集成所必需的）。只要在PdfSignatureAppearance.Close期間將該ByteBuffer的內容寫入存儲器流。

而且我看你使用

byte[] bt = memoryStream.GetBuffer(); 

請不要！除非您確定正確解釋緩衝區內容（可能包含其他垃圾數據），否則請使用

byte[] bt = memoryStream.ToArray(); 

改爲。