Monitoring battery or power supply of laptop from java

Question

I am developing an application which monitors the presence of the power supply of the laptop. If there is a power cut or restoration it will intimate me over email. It will also application monitoring and controlling over email (Basically to control my laptop from my office over email). I am done with email interfacing but I have no idea on how to monitor the power supply / battery supply from java.

If any can give some pointer on this it will be of great help.

Thanks in advance ....

Tanaka

It would help to know the platform (OS) since this is likely platform specific. – Caliche

just curious why u use the verb intimate there? It sounds odd. did you mean to use another word or is that some sort of email api? – Promote

I am using windows vista and for the "intimate" was a typo should have been "inform" :$. – Tanaka

Answer 1

You have probably already solved this problem but for the others - you can do it the way Adam Crume suggests, using an already written script battstat.bat for Windows XP and higher. Here is an example of the resulting function:

private Boolean runsOnBattery() {
    try {
        Process proc = Runtime.getRuntime().exec("cmd.exe /c battstat.bat");

        BufferedReader stdInput = new BufferedReader(
            new InputStreamReader(proc.getInputStream()));

        String s;
        while ((s = stdInput.readLine()) != null) {
            if (s.contains("mains power")) {
                return false;
            } else if (s.contains("Discharging")) {
                return true;
            }
        }
    } catch (IOException ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
    }

    return false;
}

Or you can simplify the script to return directly True/False or whatever fits.

Parhe

This is quite interesting, although it is not giving battery's current status properly this is exactly what I was looking for back then. – Tanaka

Answer 2

On linux, you can use /proc/acpi/battery/

Selfconfessed

Answer 3

A quick google search turns up a java acpi library on sourceforge. Hasn't been updated since 2004 though.

Sayyid

Answer 4

Here's code that works on Windows by using the SYSTEM_POWER_STATUS structure.

Note that you need to add jna to your (Maven) dependencies for this to work.

import java.util.ArrayList;
import java.util.List;

import com.sun.jna.Native;
import com.sun.jna.Structure;
import com.sun.jna.win32.StdCallLibrary;

public interface Kernel32 extends StdCallLibrary
{
    public Kernel32 INSTANCE = (Kernel32) Native.loadLibrary("Kernel32",
            Kernel32.class);

    public class SYSTEM_POWER_STATUS extends Structure
    {
        public byte ACLineStatus;

        @Override
        protected List<String> getFieldOrder()
        {
            ArrayList<String> fields = new ArrayList<String>();
            fields.add("ACLineStatus");

            return fields;
        }

        public boolean isPlugged()
        {
            return ACLineStatus == 1;
        }
    }

    public int GetSystemPowerStatus(SYSTEM_POWER_STATUS result);
}

In your code call it like this:

Kernel32.SYSTEM_POWER_STATUS batteryStatus = new Kernel32.SYSTEM_POWER_STATUS();
Kernel32.INSTANCE.GetSystemPowerStatus(batteryStatus);

System.out.println(batteryStatus.isPlugged());

Result:

true if charger is plugged in false otherwise

This has been derived off BalsusC's answer.

Gasteropod

Answer 5

A quick and dirty way to handle this is call a native program (via Runtime.exec(...)) and parse the output. On Windows, the native program might be VBScript that uses WMI.

Basswood