[an error occurred while processing this directive]

JSP Alert


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. 

Understand with Example

The Tutorial illustrate an elaborative example to create alert box in a JSP page. Before applying validation 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". 


Here is the code of AlertMessage.jsp

function validLogin(){
if (document.form.userName.value == ""){
alert ( "Please enter Login Name." );
return false;
if (document.form.password.value == ""){
alert ( "Please enter password." );
return false;
alert ( "Welcome User" );
return true;
<form name="form" method="post" onsubmit="return validLogin();">
<table width="250px" border=0 style="background-color:ffeeff;">
<tr><td colspan=2 align="center" style="font-weight:bold;font-size:20pt;" align="center">User Login</td>
<tr><td colspan=2>&nbsp;</td>
<tr><td style="font-size:12pt;" align="center">Login Name:</td>
<td><input type="text" name="userName" value=""></td>
<tr><td style="font-size:12pt;" align="center">Password:</td>
<td><input type="password" name="password" value=""></td>
<td><input type="submit" name="Submit" value="Login"></td>

Following output will be displayed on the browser:

If you will not enter the Login Name, an alert box displays showing error message:

If you will not enter the Password, an alert box displays showing error message:

If you will enter the username and password, an alert box displays the welcome message:


[an error occurred while processing this directive]