CrashAlerter.java

//POM can be found here http://pastebin.com/raw.php?i=YK3dd3ya
//Credits to https://github.com/Double0negative
package net.awesomepowered.crashalerter;

import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

import org.bukkit.Bukkit;
import org.bukkit.plugin.java.JavaPlugin;

public class CrashAlerter extends JavaPlugin {
	
	
	protected boolean updated = false;
	protected boolean running = true;
	protected boolean shuttingDown = false;
	protected int FreezeTime = 0;
	protected int sinceShutdown = 0;
	public int WaitTime;
	public String prefix = "[Crash] ";
	public String alertMessage;
	public String sendTo;
	
	//todo StringList for sendTo
	public void onEnable() {
		configStuff();
		startPlugin();
		printDebug();
	}
	
	public void configStuff() {
		getConfig().options().copyDefaults(true);
		saveConfig();
		WaitTime = getConfig().getInt("WaitTime");
		sendTo = getConfig().getString("Mail.sendTo");
		alertMessage = getConfig().getString("Mail.AlertMessage");
	}
	
	public void printDebug() {
		System.out.println(prefix + "Wait time until sending " + WaitTime + " seconds");
		System.out.println(prefix + "Sending email to " + sendTo);
		System.out.println(prefix + "Email message is " + alertMessage);
	}
	
	
	public void startPlugin() {
		Bukkit.getScheduler().scheduleSyncRepeatingTask(this, new Runnable() {
			public void run() {
				updated = true;
			}
		}, 1, 1);
		new Checker().start();	
	}
	
	public void onDisable() {
		running = false;
	}
	
	//Checker code by Double0Negative
	class Checker extends Thread {
		public void run() {
			while(running || shuttingDown) {
				if(!updated && !shuttingDown) {
					FreezeTime++;
					System.out.println(prefix + "Server unresponsive for " + FreezeTime + " second(s)...");
				} else {
					updated = false;
					FreezeTime = 0;
				} if(FreezeTime == WaitTime) {
					System.out.println(prefix + "Server was unresponsive for " + WaitTime + " second(s)!");
					System.out.println(prefix + "Sending alert message.");
					sendAlert(sendTo, alertMessage);
					Bukkit.shutdown();
					shuttingDown = true;
				} if(shuttingDown) {
					if(sinceShutdown == 30) {
						System.out.println(prefix + "Killing Server!");
						Runtime.getRuntime().halt(1);
					}
					System.out.println(prefix + "killing server in "+(30-sinceShutdown)+" second(s)...");
					sinceShutdown++;
				} try{ sleep(1000);} catch(Exception e) {}
			}		
		}
	}
	
	public void sendAlert(String To, String AM) {
        Properties props = new Properties();
        Session session = Session.getDefaultInstance(props, null);
        try {
            Message msg = new MimeMessage(session);
            msg.setFrom(new InternetAddress("Alerter@mysongknowwhatyoudidinthedark.org"));
            msg.addRecipient(Message.RecipientType.TO,
                             new InternetAddress(To));
            msg.setSubject("Crash Alert");
            msg.setText(AM);
            Transport.send(msg);
            System.out.println("Message sent!");

        } catch (AddressException e) {
            // ...
        } catch (MessagingException e) {
            // ...
        }
	}
}

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>net.awesomepowered</groupId>
    <artifactId>CrashAlerter</artifactId>
    <version>0.1</version>
    <name>CrashAlerter</name>
    <build>
        <defaultGoal>clean package</defaultGoal>
        <finalName>${project.name}</finalName>
        <sourceDirectory>${basedir}/src/main/java</sourceDirectory>
        <resources>
            <resource>
                <targetPath>.</targetPath>
                <filtering>true</filtering>
                <directory>${basedir}/src/main/resources/</directory>
                <includes>
                    <include>*.yml</include>
                </includes>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>1.4</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <finalName>${project.name}</finalName>
                    <artifactSet>
                        <includes>
                            <include>javax.mail:mail</include>
                        </includes>
                    </artifactSet>
                </configuration>
            </plugin>
        </plugins>
    </build>
    <repositories>
        <repository>
            <id>bukkit-repo</id>
            <url>http://repo.bukkit.org/content/groups/public</url>
        </repository> 
        <repository>
    		<id>snapshot-repository.java.net</id>
    		<name>Java.net Snapshot Repository for Maven</name>
    		<url>https://maven.java.net/content/repositories/snapshots/</url>
    	<layout>default</layout>
		</repository>
    </repositories>
    <dependencies>
        <dependency>
            <groupId>org.bukkit</groupId>
            <artifactId>bukkit</artifactId>
            <version>1.7.2-R0.1-SNAPSHOT</version>
        </dependency>
		<dependency>
			<groupId>javax.mail</groupId>
			<artifactId>mail</artifactId>
			<version>1.4.7</version>
		</dependency>
    </dependencies>
</project>