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();
      }
    }
}
}