判断tomcat是否宕机，如果宕机，则进行重启。java实现。

Detector.java:

import java.net.URL;import java.net.URLConnection;import java.util.Date;/*** * @author james**/public class Detector { private static void keepTomcatAlive() throws NullPointerException {String s;String t = new String("tomcat6");boolean isTomcatAlive = false;java.io.BufferedReader in; System.setProperty("sun.net.client.defaultConnectTimeout", "8000");   System.setProperty("sun.net.client.defaultReadTimeout", "10000");   try {	URL url = new URL("http://localhost:8080/test.jsp");	URLConnection con = url.openConnection();	in = new java.io.BufferedReader(new java.io.InputStreamReader(con.getInputStream()));	con.setConnectTimeout(1000);	con.setReadTimeout(4000);	while ((s = in.readLine()) != null) {	if (s.length() > 0) {		//accessed page successful.		return;		}	}	in.close();} catch (Exception ex) {          //ex.printStackTrace();	} try {	java.lang.Process p = java.lang.Runtime.getRuntime().exec("ps -aux");	in = new java.io.BufferedReader(new java.io.InputStreamReader(p.getInputStream()));	while ((s = in.readLine()) != null) {	if (s.startsWith(t)) {		isTomcatAlive = true;		break;		}	}	in.close();}catch (Exception e) {	e.printStackTrace();} if (isTomcatAlive) {	System.out.println("<" + new Date() + "> Tomcat is alive but not response!");	stopTomcat();} 	startTomcat();} public static void stopTomcat() {	try {		java.lang.Process p = java.lang.Runtime.getRuntime().exec("/etc/init.d/tomcat6 stop");		java.io.BufferedReader in = new java.io.BufferedReader(new java.io.InputStreamReader(p.getInputStream()));		String s;		String t = "Stopping";		boolean restart = false;		while ((s = in.readLine()) != null) {			if (s.indexOf(t) != -1) {			restart = true;			break;			}		}		System.out.println("<" + new Date() + "> Tomcat is stop " + (restart ? "OK" : "ERROR"));	} catch (Exception e) {  		e.printStackTrace();	}} public static void startTomcat() {	try {		java.lang.Process p = java.lang.Runtime.getRuntime().exec("/etc/init.d/tomcat6 start");		java.io.BufferedReader in = new java.io.BufferedReader(new java.io.InputStreamReader(p.getInputStream()));		String s;		String t = "Starting";		boolean restart = false;		while ((s = in.readLine()) != null) {		if (s.indexOf(t) != -1) {			restart = true;			break;			}		}		System.out.println("<" + new Date() + "> Tomcat is start " + (restart ? "OK" : "ERROR"));	} catch (Exception e) {		e.printStackTrace();	}} private static void debug(String msg){	System.out.println("Debug::: "+msg);} public static void main(String[] args) {	while (true) {			try {                                   debug("Detect agin <"+new Date()+">");				Detector.keepTomcatAlive();                                debug("Sleep...");				Thread.sleep(30000);			} catch (Exception ex) {                           ex.printStackTrace();			}		}} }