Java-Business-Application/C2/Database-and-validation/English-timed

Time	Narration
00:01	Welcome to the spoken-tutorial on Database and validation.
00:06	In this tutorial, we will learn to:
00:08	* Interact with database and
00:10	* Validate the fields.
00:12	Here we are using:
00:13	* Ubuntu Version 12.04
00:15	* Netbeans IDE 7.3
00:19	* JDK 1.7
00:21	* Firefox web-browser 21.0
00:24	You can use any web-browser of your choice.
00:28	To follow this tutorial, you must have knowledge of-
00:31	* Basics of Java Servlets and JSPs
00:35	* Connecting to MySQL Database from Netbeans IDE
00:39	* Creating database and tables
00:42	If not, for relevant tutorials please visit our website.
00:47	Now, let us go to Netbeans IDE.
00:52	I have started the MySQL server.
00:55	I have created a database in it named library.
01:00	I have created a table in it named Users.
01:04	I have already inserted some values into this table.
01:08	I will show them now.
01:10	For that, right click on Users and click on View Data.
01:15	Click on the Output button at the bottom.
01:19	We can see that there are 15 users here.
01:23	We can see the FirstName, Surname, Age, Gender, Email, Username and Password.
01:31	Now, let us load the JDBC driver that is Java Database Connectivity Driver.
01:39	For that, click on the Projects tab.
01:42	Right click on Libraries and click on Add Library.
01:46	Then click on MySQL JDBC Driver.
01:50	And click on AddLibrary.
01:53	This will load the JDBC Driver.
01:56	Let us run the Projectas we had done earlier.
02:00	Now, type the username as arya and password as arya*123.
02:06	Then click on Sign In.
02:08	We can see the success Greeting page.
02:12	Click on here to logout.
02:15	Now, let us switch back to the IDE.
02:17	We will go to GreetingServlet dot java.
02:21	Come to the doPost method.
02:23	First, we get the username and Password from the request using getParameter() method.
02:31	Next, we will see the code for JDBC connection.
02:35	First, we have initialized the Connection object, PreparedStatement object and Resultset object to null.
02:44	Then we register the driver in our program.
02:48	Then we create a connection to the database.
02:52	Then, we execute the prepareStatement method on the Connection object.
02:58	We give the query to get the user details from Users table.
03:03	We check if username and password are same as that which are entered in the form.
03:09	Here, the question mark denotes each field in the database.
03:15	To supply values in place of question mark, we execute the setString() method.
03:22	We do this using the PreparedStatement object.
03:26	Then we execute the executeQuery method on the Prepared statement object.
03:33	We store the result in ResultSet object.
03:37	For successful login, we display the successGreeting page.
03:43	For this, we use the RequestDispatcher interface.
03:48	We use the getRequestDispatcher() method on the request to obtain the RequestDispatcher object.
03:56	We then invoke the forward() method on RequestDispatcher. object.
04:02	In this way, we forward to successGreeting dot jsp.
04:07	Now switch back to the slides.
04:10	Let us learn something about RequestDispatcher interface.
04:15	* This interface provides the facility of dispatching the request to another resource.
04:22	* The resource can be html, servlet or jsp.
04:26	Now, let us come back to the IDE.
04:29	Let us come to successGreeting dot'jsp.'
04:33	Here, we are displaying the success message You have successfully logged in.
04:38	Now, come back to the browser.
04:41	Type a username and password that we have not included in the database.
04:47	So, let me type abc as the username and abc123* as the password.
04:56	Then click on Sign In.
04:59	We can see that we get the error message on the same page itself.
05:03	"Please correct the following error!!! Invalid username or password" .
05:09	Now, let us see the code for this.
05:12	So, switch back to the IDE.
05:14	Go to GreetingServlet dot java.
05:17	If the validation fails then we should display the error message.
05:22	First, we have initialized a List of errorMsgs.
05:27	We set the variable errorMsgs into the request scope using setAttribute method.
05:35	Here, errorMsgs is the attribute name.
05:39	We have initialized a String variable id to null.
05:44	Then, we check if the user exists in the database.
05:48	If yes, we store the value in the variable id.
05:53	Else, we add the error "Invalid username or password" to errorMsgs list.
06:00	If the errorMsgs list is not empty then we display the error messages on index dot jsp.
06:09	So, we have to redirect to index dot jsp.
06:13	We have already seen how to redirect to another page using RequestDispatcher.
06:20	Note that we have included this code inside the try catch block to handle exception scenarios.
06:27	Now, we will see how to fetch errorMsgs variable in index dot jsp.
06:34	First, we obtain the value of the attribute "errorMsgs".
06:38	This is done using getAttribute method on the request.
06:44	Note that we have included the Java code within the opening tag which is less than sign percentage sign and the closing tag percentage sign and greater than sign.
06:57	This block of code is known as scriptlet.
07:02	It contains Java code which is executed every time JSP is invoked.
07:08	If the value of errorMsgs is not null then we display this message.
07:15	"Please correct the following errors".
07:18	Then we iterate through the list of errorMsgs.
07:23	We then display the error messages as a list.
07:27	This is how we display the error messages on index dot jsp.
07:32	Now, let us see how to add a user into the database.
07:37	Before adding a user into the database, we have to create a model for the User table.
07:44	Now, let us see what a model is.
07:48	A model :
07:49	* Represents the underlying logical structure of data in a software application.
07:55	* A Java class with attributes and setters and getters for them.
08:00	In this way, we can consider model as a whole instead of the individual attributes.
08:07	Now, switch back to Netbeans IDE.
08:11	I have already created the model User dot java.
08:16	Note that we have created this Java class inside the package org dot spokentutorial dot model.
08:24	We have the following attributes- firstName, surname, age, gender, email, username and password.
08:33	We have initialized them to empty values.
08:37	Then we have a parameterized constructor.
08:41	We also have the default constructor.
08:44	We define the getFirstName method.
08:47	We also define the setFirstName method.
08:51	Similarly, we define the set and get methods on each of the attributes.
08:57	Come back to the browser.
08:59	Now, let us click on here link to register.
09:03	Type all the fields in the Registration page.
09:07	Then click on Add User.
09:10	We get Add User Success page.
09:14	We get the message: "Your request to add harshita was successful".
09:20	Here harshita was the username that we have given.
09:24	Now, let us see how this is done.
09:28	So, switch back to the IDE.
09:30	Go to AddUserServlet dot java.
09:35	The steps are similar to that we had followed in GreetingServlet dot java.
09:40	First, we get the form parameters using the getParameter method.
09:46	We initialize variable user as instance of User model with individual attributes.
09:53	We set the variable user into the request scope using setAttribute method.
10:01	If there are no errors while filling the form, we execute the query to insert the values into the Users table.
10:10	Then we forward to successUser page.
10:15	Now, let us come to successUser dot jsp.
10:19	First, we have imported User dot java.
10:24	This line of code is called directive in JSP.
10:28	A JSP directive starts with opening tag- 'less than sign percentage sign and at the rate sign' and ends with closing tag- 'percentage sign and greater than sign'.
10:42	This one is a page directive.
10:45	The page directive contains a list of all imported packages.
10:50	We get the value of the attribute user and store it as the User object.
10:57	Then, we have the success message here.
11:00	Here, we have retrieved the Username.
11:04	We have used the getUsername() method on the request object.
11:09	We have done this using scriptlet tags.
11:12	Now, let us come back to the browser.
11:15	We will try to add a user already present in the database.
11:20	So, I will try to add harshita again.
11:24	We can see that we get the error message "Please correct the following errors!!!! Duplicate entry 'harshita' for key 'UserName'.
11:33	Now, let us register for a user once again.
11:37	Here, I have filled up the form now.
11:40	I have created a mistake in the Age field.
11:44	I have typed ab instead of a valid number.
11:48	Now, click on Add User.
11:51	We see, we get the error message- "The age must be a positive integer".
11:57	Now, let us see how this is done.
12:00	Switch back to the IDE.
12:03	Open AddUserServlet dot java.
12:08	Here also, we have created a list for errorMsgs.
12:11	Then we set the variable errorMsgs into the request scope using setAttribute method.
12:18	Then, we have declared ageUser of type integer and we have initialized it to -1 (minus one).
12:26	Inside the try catch block, we have used parseInt method.
12:31	This will return an integer, given a string representation of number as input.
12:37	So, here we validate that the age field contains a valid positive integer.
12:44	If the validation fails then we add error message to errorMsgs list.
12:51	The age must be a positive integer.
12:54	Similarly, we have to validate all the other fields to have valid data.
13:01	If the errorMsgs list is not empty then we will display the errorMsgs on addUser dot jsp itself.
13:09	We have already seen how to do this using the RequestDispatcher.
13:15	Now, let us come to addUser dot jsp.
13:19	Here also, first we have imported User dot java.
13:24	Inside the scriptlet tags, we have created an object of type User.
13:31	Then we get the value of the attribute errorMsgs using getAttribute method.
13:38	We check if this value is equal to null.
13:43	If it is not equal to null then we display the error message just as we had done for index dot jsp.
13:51	If not, we will get the value of the attribute user from request using 'User' model.
13:59	Then we have the form.
14:01	The form tag has action as AddUserServlet and method as POST.
14:07	The first field is First Name of input type as text , name as firstName and value as user dot getFirstName.
14:18	Here, we are initializing the value of firstName to empty string.
14:24	Similarly, you have to do for other fields.
14:28	We also have a submit button and value as Add User.
14:33	This is how we validate the fields in addUser.jsp.
14:38	You can try out different errors on Add User page.
14:42	Now, let us see if the user harshita has been added to the database.
14:49	So, come back to the Users table. We can see that harshita is added to the database.
14:56	In this tutorial we have learnt:
14:58	Database connectivity and
15:00	Field validation.
15:02	To know more about the spoken tutorial project, watch the video available at the following link.
15:07	It summarizes the Spoken Tutorial Project.
15:11	If you do not have good bandwidth, you can download and watch it.
15:15	The Spoken Tutorial Project team:
15:17	Conducts workshops using spoken tutorials.
15:20	Gives certificates for those who pass an online test.
15:23	For more details, please write to: contact at spoken hyphen tutorial dot org.
15:29	Spoken Tutorial Project is a part of the "Talk to a Teacher Project".
15:32	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
15:38	More information on this mission is available at spoken-tutorial.org/NMEICT-intro
15:48	The Library Management System has been contributed by a leading software MNC through their "Corporate Social Responsibility Programme".
15:57	They have also validated the content for this spoken tutorial.
16:02	This is Arya Ratish from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

Nancyvarkey, PoojaMoolya, Pratik kamble, Sandhya.np14, Shruti arya