获取并设置itext pdf文档的元数据

Question

我有一个iText Document对象,我想在其中写入一些元数据或从中读取.
我怎样才能做到这一点？

想象一下,该文档正在传递给以下方法:

public void prePreccess(Object document) {
    Document pdfDocument =   ((Document) document);
    //What to do here with pdfDocument?
}

Answer 1

您想填充PDF的信息词典吗？这在MetadataPdf示例中进行了解释:

// step 1
Document document = new Document();
// step 2
PdfWriter.getInstance(document, new FileOutputStream(filename));
// step 3
document.addTitle("Hello World example");
document.addAuthor("Bruno Lowagie");
document.addSubject("This example shows how to add metadata");
document.addKeywords("Metadata, iText, PDF");
document.addCreator("My program using iText");
document.open();
// step 4
document.add(new Paragraph("Hello World"));
// step 5
document.close();

是否要设置XMP元数据？这在MetadataXmp示例中进行了解释:

// step 1
Document document = new Document();
// step 2
PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(RESULT1));
ByteArrayOutputStream os = new ByteArrayOutputStream();
XmpWriter xmp = new XmpWriter(os);
XmpSchema dc = new com.itextpdf.text.xml.xmp.DublinCoreSchema();
XmpArray subject = new XmpArray(XmpArray.UNORDERED);
subject.add("Hello World");
subject.add("XMP & Metadata");
subject.add("Metadata");
dc.setProperty(DublinCoreSchema.SUBJECT, subject);
xmp.addRdfDescription(dc);
PdfSchema pdf = new PdfSchema();
pdf.setProperty(PdfSchema.KEYWORDS, "Hello World, XMP, Metadata");
pdf.setProperty(PdfSchema.VERSION, "1.4");
xmp.addRdfDescription(pdf);
xmp.close();
writer.setXmpMetadata(os.toByteArray());
// step 3
document.open();
// step 4
document.add(new Paragraph("Hello World"));
// step 5
document.close();

请注意,不推荐使用此方法:我们最近已经替换了XMP功能,但我们仍然需要使用新代码编写一些示例.

也许你想设置填充信息字典并同时创建XMP元数据:

// step 1
Document document = new Document();
// step 2
PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(filename));
document.addTitle("Hello World example");
document.addSubject("This example shows how to add metadata & XMP");
document.addKeywords("Metadata, iText, step 3");
document.addCreator("My program using 'iText'");
document.addAuthor("Bruno Lowagie");
writer.createXmpMetadata();
// step 3
document.open();
// step 4
document.add(new Paragraph("Hello World"));
// step 5
document.close();

如果我是你,我会使用这个选项,因为它是最完整的解决方案.

您不应该从Document对象中读取元数据.

您可以从现有PDF中读取XMP流,如下所示:

public void readXmpMetadata(String src, String dest) throws IOException {
    PdfReader reader = new PdfReader(src);
    FileOutputStream fos = new FileOutputStream(dest);
    byte[] b = reader.getMetadata();
    fos.write(b, 0, b.length);
    fos.flush();
    fos.close();
    reader.close();
}

您可以像这样读取信息字典中的条目:

PdfReader reader = new PdfReader(src);
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
Map<String, String> info = reader.getInfo();

该 info对象将包含一系列键和值,这些键和值作为元数据存储在PDF中.