如何使用itext删除PDF的附件 [英] How to delete attachment of PDF using itext

问题描述

我是pdf的新手，我使用以下代码将文件嵌入到pdf中。但是，我想编写另一个程序来删除嵌入文件。我可以知道怎么办吗？非常感谢！

  public void addAttachments（String src，String dest，String [] attachments）抛出IOException，DocumentException {
 PdfReader reader = new PdfReader（src）; 
 PdfStamper stamper = new PdfStamper（reader，new FileOutputStream（dest））; 
 for（int i = 0; i< attachments.length; i ++）{
 addAttachment（stamper.getWriter（），new File（attachments [i]））; 
} 
 stamper.close（）; 
} 
 
 protected void addAttachment（PdfWriter writer，File src）抛出IOException {
 PdfFileSpecification fs = 
 PdfFileSpecification.fileEmbedded（writer，src.getAbsolutePath（），src .getName（），null）; 
 writer.addFileAttachment（src.getName（）。substring（0，src.getName（）。indexOf（'。'）），fs）; 
} 
  

解决方案

让我先重写你的用于添加嵌入文件的代码。

  public void manipulatePdf（String src，String dest）抛出IOException，DocumentException {
 PdfReader reader = new PdfReader（src）; 
 PdfStamper stamper = new PdfStamper（reader，new FileOutputStream（dest））; 
 PdfFileSpecification fs = PdfFileSpecification.fileEmbedded（
 stamper.getWriter（），null，test.txt，Some test.getBytes（））; 
 stamper.addFileAttachment（some test file，fs）; 
 stamper.close（）; 
} 
  

您可以在此处找到完整的代码示例：示例的代码，看看我们如何在面向对象的情况下进行导航PDF格式的文件格式：

  public void manipulatePdf（String src，String dest）抛出IOException，DocumentException {
 PdfReader reader = new PdfReader（src）; 
 PdfDictionary root = reader.getCatalog（）; 
 PdfDictionary names = root.getAsDict（PdfName.NAMES）; 
 PdfDictionary embeddedFiles = names.getAsDict（PdfName.EMBEDDEDFILES）; 
 PdfArray namesArray = embeddedFiles.getAsArray（PdfName.NAMES）; 
 namesArray.remove（0）; 
 namesArray.remove（0）; 
 PdfStamper stamper = new PdfStamper（reader，new FileOutputStream（dest））; 
 stamper.close（）; 
} 
  

如您所见，我们从文档的根目录开始（又名目录）我们通过名称和 EmbeddedFiles 走到名称数组。我知道我要删除的嵌入文件是数组中的第一个，我通过删除索引为0的元素两次删除名称和值。这首先删除描述，然后删除对文件的引用。附件现已消失：

由于我的示例中只有一个嵌入文件，所以当我查看PDF时，我现在看到一个空数组：

如果要一次删除所有嵌入文件，代码就更容易了。这显示在 RemoveEmbeddedFiles 示例中：

  public void manipulatePdf（String src，String dest）抛出IOException，DocumentException {
 PdfReader reader = new PdfReader（src）; 
 PdfDictionary root = reader.getCatalog（）; 
 PdfDictionary names = root.getAsDict（PdfName.NAMES）; 
 names.remove（PdfName.EMBEDDEDFILES）; 
 PdfStamper stamper = new PdfStamper（reader，new FileOutputStream（dest））; 
 stamper.close（）; 
} 
  

现在我们甚至不查看<$ c $的条目c> EmbeddedFiles 字典。 名称词典中不再有这样的条目：

I am new to pdf and i use the following code to embed the file to pdf. However, I want to write another program to delete the embeded files. May I know how can I do it? Really Thanks!

public void addAttachments(String src, String dest, String[] attachments) throws IOException,DocumentException {
PdfReader reader = new PdfReader(src);
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
for (int i = 0; i < attachments.length; i++) {
        addAttachment(stamper.getWriter(), new File(attachments[i]));
                                  }
                                  stamper.close();
                                }

                                protected void addAttachment(PdfWriter writer, File src) throws IOException {
                                  PdfFileSpecification fs =
                                    PdfFileSpecification.fileEmbedded(writer, src.getAbsolutePath(), src.getName(), null);
                                  writer.addFileAttachment(src.getName().substring(0, src.getName().indexOf('.')), fs);
                                }

解决方案

Let me start by rewriting your code to add an embedded file.

public void manipulatePdf(String src, String dest) throws IOException, DocumentException {
    PdfReader reader = new PdfReader(src);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    PdfFileSpecification fs = PdfFileSpecification.fileEmbedded(
            stamper.getWriter(), null, "test.txt", "Some test".getBytes());
    stamper.addFileAttachment("some test file", fs);
    stamper.close();
}

You can find the full code sample here: AddEmbeddedFile

Now when we look at the Attachments panel of the resulting PDF, we see an attachment test.txt with description "some test file":

After you have added this file, you now want to remove it. To do this, please use RUPS and take a look inside:

This gives us a hint on where to find the embedded file. Take a look at the code of the RemoveEmbeddedFile example to see how we navigate through the object-oriented file format that PDF is:

public void manipulatePdf(String src, String dest) throws IOException, DocumentException {
    PdfReader reader = new PdfReader(src);
    PdfDictionary root = reader.getCatalog();
    PdfDictionary names = root.getAsDict(PdfName.NAMES);
    PdfDictionary embeddedFiles = names.getAsDict(PdfName.EMBEDDEDFILES);
    PdfArray namesArray = embeddedFiles.getAsArray(PdfName.NAMES);
    namesArray.remove(0);
    namesArray.remove(0);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.close();
}

As you can see, we start at the root of the document (aka the catalog) and we walk via Names and EmbeddedFiles to the Names array. As I know that the embedded file I want to remove is the first in the array, I remove the name and value by removing the element with index 0 twice. This first removes the description, then the reference to the file. The attachment is now gone:

As there was only one embedded file in my example, I now see an empty array when I look inside the PDF:

If you want to remove all the embedded files at once, the code is even easier. That is shown in the RemoveEmbeddedFiles example:

public void manipulatePdf(String src, String dest) throws IOException, DocumentException {
    PdfReader reader = new PdfReader(src);
    PdfDictionary root = reader.getCatalog();
    PdfDictionary names = root.getAsDict(PdfName.NAMES);
    names.remove(PdfName.EMBEDDEDFILES);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.close();
}

Now we don't even look at the entries of the EmbeddedFiles dictionary. There is no longer such an entry in the Names dictionary:

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