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();      }    }}}