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

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Revision as of 12:49, 12 July 2015

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 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 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 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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