Demo

Here is an example to load and manipulate a LibreOffice document with multiple placeholders. Some of these placeholders stand for simple texts, other represent another document that shall be imported. Images can also represent placeholders that shall be exchanged: This code snipped reads the template document above and replaces the placeholders with data

// Prepare document and engine
    OdtContainer doc = new OdtContainer(is);
    OdtEngine engine = new OdtEngine();
    
    // Alias placeholders
    engine.registerStringReplacement("addHeaderAndFooter", "${Export $resource:\"master\"} ");
    engine.registerStringReplacement("membersTable", "${Import $resource:\"membersTable\"} ");
    
    // Variables / Data
    engine.pushLeafVariable("membersTable", readResource("membertable.odt"));
    engine.pushLeafVariable("master", readResource("master.odt"));
    engine.pushLeafVariable("signatureImage", readResource("signature.png"));
    engine.pushVariable("persons", createPersonsData());
    engine.pushVariable("address", "Mr. Peter Silie\nKochstrasse 42\n38106 Braunschweig");
    engine.pushVariable("contact", "Mr. Silie");
    engine.pushVariable("signature", "Jon Sutton");
    
    // Execute the engine
    engine.run(doc);
    doc.save(os);

And you get a filled document like this one: When LibreOffice is installed and LIBREOFFICE environment variable is set correctly you can also generate a PDF:

doc.writePDF(pos);

You can find the comple JUnit test case of this demo right here:
Github - Underdocx - DemoTest