Get XML Metadata

In this guide getting the XML metadata of root catalog for PDF files will be demonstrated.

Before you begin #

You should get your API key from your UniCloud account.

If this is your first time using UniPDF SDK, follow this guide to set up a local development environment.

Project setup #

Clone the project repository #

In your terminal, clone examples repository. It contains the Go code we will be using for this guide.

git clone https://github.com/unidoc/unipdf-examples.git

Navigate to the metadata folder in the unipdf-examples directory.

cd unipdf-examples/metadata

Configure environment variables #

Replace the UNIDOC_LICENSE_API_KEY with your API credentials from your UniCloud account.

Linux/Mac #

export UNIDOC_LICENSE_API_KEY=PUT_YOUR_API_KEY_HERE

Windows #

set UNIDOC_LICENSE_API_KEY=PUT_YOUR_API_KEY_HERE

How it works #

The following example code gets metadata from pdf file.

The import section defined in lines 13-24 imports necessary unipdf packages and other go libraries. The init function in lines 26-33 loads UNIDOC_LICENSE_API_KEY from system environment and authenticates your request.

The main function is defined in lines 35-52 and is used to get the XML pdf metadata. In lines 36-42 the input files is parsed from the command line argument. The loop in lines 43-51 iterates through each input file and prints XML metadata for each pdf document using printXMLMetadataForPdf.

The printXMLMetadataForPdf function defined in lines 54-98 is used to get the XML metadata and print it to standard output. In this function in lines 55-64 a new model.PdfReader is created using the input file given as an argument of the function.

In lines 66-69 the root catalog is obtained using the function getRootCatalog. The code in lines 72-84 gets the XML metadata. Then it is decoded into xmp metadata format in lines 87-92 using xmlDecoder.Decode(&xmp). Finally the metadata is printed using xmp.print() in line 95.

The getRootCatalog function defined in lines 102-123 returns the root catalog PdfObjectDictionary type. In lines 127-138 the function resolve which is used to resolve reference objects is defined. In lines 143-151 the xmpMetadata type is defined which is used to hold the xmp metadata. Two methods of this xmpMetadata type, namely keyValMap() and print() are defined in lines 155-180.

Run the code #

go run pdf_metadata_get_xml.go <input1.pdf> <input2.pdf> ...