Capstone

JSP Alert Example
Everything is fine. One fine day, you do some changes in your webapp and restart tomcat. Then you get this error. LifecycleException: service.getName(): "Catalina"; Protocol handler start failed: `java.net.BindException: Permission denied :80. What does this mean??? (The complete error is given below for your reference)
This is simply because of some permission issues. In linux, ports 1-1023 are privileged. Only root is allowed to bind to them. But in your startup script for tomcat, you will normally use the tomcat user to start tomcat. That is why you get this error. To resolve this and to start tomcat as root you can do this.
1. Open the file /etc/rc.d/init.d/tomcat6
2. Look for this line # $SU - $TOMCAT_USER -c "${TOMCAT_SCRIPT} start-security" and replace it with $SU - root -c "${TOMCAT_SCRIPT} start-security"
3. Look for this line as well just below the above line. $SU - $TOMCAT_USER -c "${TOMCAT_SCRIPT} start" >> $TOMCAT_LOG 2>&1 and replace it with $SU - root -c "${TOMCAT_SCRIPT} start" >> $TOMCAT_LOG 2>&1
4. Save the file and restart tomcat service
That't it. You're done. what you did is to start tomcat as root user and the root user has the privilege to open port 80. Everything should work now. java.net.BindException: Permission denied :80 at org.apache.tomcat.util.net.JIoEndpoint.init(JIoEndpoint.java:549) at org.apache.tomcat.util.net.JIoEndpoint.start(JIoEndpoint.java:565) at org.apache.coyote.http11.Http11Protocol.start(Http11Protocol.java:203) at org.apache.catalina.connector.Connector.start(Connector.java:1087) at org.apache.catalina.core.StandardService.start(StandardService.java:534) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:581) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
Caused by: java.net.BindException: Permission denied at java.net.PlainSocketImpl.socketBind(Native Method) at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:365) at java.net.ServerSocket.bind(ServerSocket.java:319) at java.net.ServerSocket.(ServerSocket.java:185) at java.net.ServerSocket.(ServerSocket.java:141) at org.apache.tomcat.util.net.DefaultServerSocketFactory.createSocket(DefaultServerSocketFactory.java:50) at org.apache.tomcat.util.net.JIoEndpoint.init(JIoEndpoint.java:538) ... 12 more
0:11:56 org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start:
LifecycleException: service.getName(): "Catalina"; Protocol handler start failed: `java.net.BindException: Permission denied :80 at org.apache.catalina.connector.Connector.start(Connector.java:1094) at org.apache.catalina.core.StandardService.start(StandardService.java:534) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:581) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
0:11:56 org.apache.catalina.startup.Catalina start`
JSP Alert is used to put the validation on login page for the users. The example in this Tutorial provides you to create the validation on the login form using Javascript method in JSP page.
The Tutorial illustrate an elaborative example to create alert box in a JSP page. We create a JSP file "AlertMessage.jsp". The Alert Message contains the code for User Login page that include the 'LoginName' and 'Password'. To apply validation we make use of javascript method in AlertMessage.jsp to validate the LoginName and password. The on submit button in JSP calls a JavaScript's function validLogin( ). The function validlogin ( ) is used to validate the username and password in JSP. If the username and password field is not inserted by the user then this will display error message using "alert()". The function also ensures that the field username and password must not be empty. Otherwise it will displays the message "Welcome User".
reference:http://www.pageresource.com/jscript/jalert.htm