Difference between revisions of "Java-Business-Application/C2/Database-and-validation/English-timed"

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Revision as of 16:40, 19 September 2014

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
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 Add Library.
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 arya123*.
02.06 Then click on Sign In.
02.08 We can see the successGreeting page.
02.12 Click on hereto 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 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 is same as that which is 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 resouce
04.22 The resorce 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 messages.
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, 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 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, 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 Similary 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 user tables.
10.10 Then we forward to success user 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 add harshita again.
11.24 We can see that we get the error message Please correct the following errors!!1 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 initialize it to -1
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 that all the other fields too 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 the 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 the Add User page.
14.42 Now let us see that the user harshita has been added to the database.
14.49 So come back to user 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

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