如何通过Java检查打印机是否已连接到PC？

Question

I am able to get the name of printer which I had installed previously on my PC.But now its not physically connected to my pc. How should I check it first before moving to Print() in Java.

Answer 1

You can use PrinterState attribute if it is supported by your printer.

Something like this:

PrintServiceAttributeSet printServiceAttributes = selectedService.getAttributes();
PrinterState printerState = (PrinterState) printServiceAttributes.get(PrinterState.class);
       if (printerState != null){
          System.out.println(printerName + " is online");
       } 
       else {
          System.out.println(printerName + " is offline");
       }

Answer 2

Take a look at the javax.print API. A good starting point would be PrintServiceLookup .

Answer 3

There is no PrinterState Attribute in Set. But you can load library Winspool.drv and ask it for attributes. There is int Attributes@68=, which has a40 value for online and e40 value for offline printer.

Start there - https://msdn.microsoft.com/cs-cz/library/windows/desktop/dd144911(v=vs.85).aspx .

Use these classes and then get WinspoolUtilExt.getPrinterInfo2(ps.getName()).toString() and there is an attribute.

public interface WinspoolExt extends Winspool {

    WinspoolExt INSTANCE = (WinspoolExt) Native.loadLibrary("Winspool.drv", WinspoolExt.class, W32APIOptions.UNICODE_OPTIONS);

    boolean GetPrinter(HANDLE hPrinter, int Level, Pointer pPrinter, int cbBuf, IntByReference pcbNeeded);

    boolean OpenPrinter(String pPrinterName, HANDLEByReference phPrinter, Pointer pDefault);

    public static class PRINTER_INFO_2 extends Structure {
        public String pServerName;
        public String pPrinterName;
        public String pShareName;
        public String pPortName;
        public String pDriverName;
        public String pComment;
        public String pLocation;
        public INT_PTR pDevMode;
        public String pSepFile;
        public String pPrintProcessor;
        public String pDatatype;
        public String pParameters;
        public INT_PTR pSecurityDescriptor;
        public int Attributes;
        public int Priority;
        public int DefaultPriority;
        public int StartTime;
        public int UntilTime;
        public int Status;
        public int cJobs;
        public int AveragePPM;

        protected List<String> getFieldOrder() {
            return Arrays.asList(new String[] { "pServerName", "pPrinterName", "pShareName", "pPortName", "pDriverName", "pComment", "pLocation", "pDevMode", "pSepFile", "pPrintProcessor", "pDatatype", "pParameters", "pSecurityDescriptor", "Attributes", "Priority", "DefaultPriority", "StartTime", "UntilTime", "Status", "cJobs", "AveragePPM" });
        }

        public PRINTER_INFO_2() {
        }

        public PRINTER_INFO_2(int size) {
            super(new Memory(size));
        }
    }
}

public class WinspoolUtilExt extends WinspoolUtil {
    public static PRINTER_INFO_2 getPrinterInfo2(String printerName) {
        IntByReference pcbNeeded = new IntByReference();
        IntByReference pcReturned = new IntByReference();
        HANDLEByReference pHandle = new HANDLEByReference();

        WinspoolExt.INSTANCE.OpenPrinter(printerName, pHandle, (Pointer) null);

        WinspoolExt.INSTANCE.GetPrinter(pHandle.getValue(), 2, null, 0, pcbNeeded);
        if (pcbNeeded.getValue() <= 0) {
            return new PRINTER_INFO_2();
        }

        PRINTER_INFO_2 pinfo2 = new PRINTER_INFO_2(pcbNeeded.getValue());

        WinspoolExt.INSTANCE.GetPrinter(pHandle.getValue(), 2, pinfo2.getPointer(), pcbNeeded.getValue(), pcReturned);

        pinfo2.read();
        return (PRINTER_INFO_2) pinfo2;
    }
}

Maven dependencies:

        <dependency>
            <groupId>net.java.dev.jna</groupId>
            <artifactId>jna</artifactId>
        </dependency>
        <dependency>
            <groupId>net.java.dev.jna</groupId>
            <artifactId>jna-platform</artifactId>
            <version>${jna.version}</version>
        </dependency>

Answer 4

Another way is to use PowerShell and query:

Get-WmiObject -Query "Select * From Win32_PnPEntity where deviceid like 'USBPRINT\\%' and caption like '%Canon%'"

This way, you get result only if printer is connected.

You can query WMI from Java with many libraries, search "WMI Java library".