无需FileInputStream，用Java打印iText生成的PDF文档

Great question! You don't need to save your generated PDF to a file just to print it—you can handle everything entirely in memory, skipping the filesystem step altogether. Here's how to do it using a ByteArrayOutputStream to capture the PDF content from iText, then converting that to a ByteArrayInputStream for the printing API:

Step-by-Step Explanation #

1. Capture PDF in Memory: Instead of writing the PDF to a file with FileOutputStream, use a ByteArrayOutputStream to store the generated PDF content directly in memory.
2. Convert to Input Stream: Turn the ByteArrayOutputStream into a ByteArrayInputStream—this gives you the InputStream the printing API needs without reading from a local file.
3. Set Up and Submit Print Job: Use the standard Java Print Service API with your in-memory input stream to print the PDF.

Full Code Example #

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Phrase;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPTable;
import com.itextpdf.text.pdf.PdfWriter;

import javax.print.*;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class InMemoryPdfPrinter {
    public static void main(String[] args) throws DocumentException, IOException, PrintException {
        // 1. Generate your PDF directly into memory
        ByteArrayOutputStream pdfOutputStream = new ByteArrayOutputStream();
        Document document = new Document();
        PdfWriter.getInstance(document, pdfOutputStream);

        document.open();

        // Add your existing table and data here (example table included)
        PdfPTable housingTable = new PdfPTable(3);
        housingTable.addCell(new PdfPCell(new Phrase("Property ID")));
        housingTable.addCell(new PdfPCell(new Phrase("Address")));
        housingTable.addCell(new PdfPCell(new Phrase("Status")));
        housingTable.addCell("H-001");
        housingTable.addCell("123 Main St");
        housingTable.addCell("Occupied");
        housingTable.addCell("H-002");
        housingTable.addCell("456 Oak Ave");
        housingTable.addCell("Vacant");

        document.add(housingTable);
        document.close();

        // 2. Convert the in-memory PDF to an InputStream
        ByteArrayInputStream pdfInputStream = new ByteArrayInputStream(pdfOutputStream.toByteArray());

        // 3. Configure and submit the print job
        DocFlavor printFlavor = DocFlavor.INPUT_STREAM.AUTOSENSE;
        PrintService[] availablePrinters = PrintServiceLookup.lookupPrintServices(printFlavor, null);

        if (availablePrinters.length == 0) {
            System.err.println("No printers detected on the system.");
            return;
        }

        // Use the first available printer (you can let users select one if needed)
        PrintService selectedPrinter = availablePrinters[0];
        Doc printDoc = new SimpleDoc(pdfInputStream, printFlavor, null);
        DocPrintJob printJob = selectedPrinter.createPrintJob();

        printJob.print(printDoc, null);
        System.out.println("Print job sent to " + selectedPrinter.getName());
    }
}

Key Notes #

• No File I/O: This approach avoids writing the PDF to disk and reading it back, which is faster and cleaner for temporary documents.
• Memory Considerations: If your PDF is extremely large, keep an eye on memory usage—but for most standard reports (like your housing report), this won't be an issue.
• Printer Selection: The example uses the first available printer, but you can extend it to let users choose from the list of availablePrinters if needed.

内容的提问来源于stack exchange，提问作者Mohammed Amer