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

| 00:01

| Welcome to the spoken-tutorial on''' Database and validation.'''

| In this tutorial we will learn to:

| '''Interact with database'''

| 00:10

| '''Validate the fields'''

|Here we are using

| 00:13

| '''Ubuntu Version''' 12.04

| 00:15

| '''Netbeans IDE''' 7.3

 

| 00:21

| '''Firefox''' web-browser 21.0

|To follow this tutorial you must have knowledge of

| Basics of '''Java Servlets''' and '''JSPs'''

| 00:35

| Connecting to '''MySQL Database '''  from '''Netbeans IDE'''

| Creating '''database '''and '''tables'''

| 00:47

| I have started the '''MySQL server.'''

| 00:55

| I have created a '''database''' in it named  '''library.'''

| 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.

| For that, right click on '''Users '''and click on '''View Data.'''

| 01:19

| We can see that there are '''15 users '''here.

|   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

| 01:42

| Right click on '''Libraries''' and  Click on '''Add Library.'''

| 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 '''Project'''as 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 '''here''' to logout.

| 02:15

| Now, let us switch back to the '''IDE.'''

| 02:17

| We will go to '''GreetingServlet '''''dot '''''java.'''

| 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.'''

| We have initialized the '''Connection object, PreparedStatement object '''and '''Resultset object '''to '''null.'''

| 02:48

| Then we create a connection to the '''database.'''

| Then, we execute the '''prepareStatement method '''on the '''Connection object.'''

| We give the query to get the '''user details '''from '''Users table.'''

| 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.

| To supply values in place of question mark, we execute the '''setString method.'''

| 03:26

| Then we execute the '''executeQuery method '''on the '''Prepared statement''' object

|We store  the result in '''ResultSet''' object

| 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.'''

|  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

|Let us learn something about '''RequestDispatcher interface'''

| This  interface provides the facility of dispatching  the '''request''' to another resouce

| The resorce can be html, servlet, or jsp

| Now let us come back to the IDE

|  We can see that we get the '''error message '''on the same page itself.

| '''Please correct the following error!!! Invalid username or password'''

| So, Switch back to the '''IDE'''

|  Go to '''GreetingServlet '''''dot '''''java.'''

|  If the '''validation '''fails, then we should display the '''error messages.'''

| First we have  initialized a '''List '''of '''errorMsgs.'''

|  We set the variable '''errorMsgs '''into the '''request scope''' using '''setAttribute '''method'''.'''

|  Here, '''errorMsgs '''is the '''attribute name.'''

|  Else, we add the error '''Invalid username''' or '''password''' to '''errorMsgs list.'''

|  If the '''errorMsgs list '''is not empty, we display the '''error messages '''on '''index '''''dot '''''jsp.'''

| So, we have to redirect to '''index ''' '''dot ''' '''jsp.'''

| We have already seen how to redirect to another page using '''RequestDispatcher.'''

|  Now, we will see how to fetch '''errorMsgs '''variable in '''index '''''dot '''''jsp.'''

|  First, we obtain the value of the '''attribute errorMsgs.'''

| 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.'''

|  If the value of '''errorMsgs '''is not null, then we  display this message.

| '''Please correct the following errors.'''

|  Then we iterate through list of  '''errorMsgs.'''

|  This is how we display the '''error messages''' on  '''index ''' '''dot ''' '''jsp.'''

| Now, Let us see what a '''model '''is.

| A '''model :'''

 

|  Represents the underlying, logical structure of data in a '''software application.'''

| A '''Java class '''with '''attributes '''and '''setters '''and '''getters '''for them.

|  Now, Switch back to '''Netbeans IDE.'''

| I have already created the model '''User '''''dot '''''java.'''

|  Note that we have created this '''Java class '''inside the '''package org ''dot ''spokentutorial ''dot ''model.'''

|  We have the following '''attributes firstName, surname, age, gender, email, username, password.'''

|  Similary we define the '''set '''and '''get methods '''on each of the '''attributes.'''

|  Now, let us click on '''here link '''to '''register.'''

|  Type all the fields in the '''Registration Page.'''

|  We get  '''Add User Success Page.'''

|  We get  the message ''' Your request to add harshita was successful.'''

|  Here '''harshita''' was the '''username''' that we have given  

|  So switch back to the '''IDE.'''

|  The steps are similar to that we had followed in '''GreetingServlet '''''dot '''''java.'''

|  First we get the '''form parameters''' using the '''getParameter method.'''

|  We initialize variable '''user '''as '''instance '''of '''User Model '''with individual '''attributes.'''

|  If there are no errors while filling  the '''form, '''we execute the query to  insert the values into the user tables.

|  Then we forward to '''success user page'''

|  Now, let us come to '''successUser '''''dot '''''jsp.'''

|  First, we have imported '''User '''''dot '''''java.'''

|  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.'''

|  Then,We have the '''success message '''here.

| We have''' '''used the '''getUsername() method '''on the '''request object.'''

|  So, I will add '''harshita '''again.

|  We can see that we get the error message '''Please correct the following errors!!1 Duplicate entry 'harshita' for key username.'''

| Now, Let us register for a user once again.

|  Here, I have filled up the form now.

|  I have created a mistake in the '''Age''' field.

|  We see we get the error message '''The age must be a positive integer.'''

|  Open '''AddUserServlet '''''dot '''''java.'''

|  Here also, we have created a '''list for errorMsgs.'''

|  Then, we have declared '''ageUser '''of type '''integer''' and we have initialize it to -1

|  Inside the '''try catch block '''we have used '''parseInt method.'''

| This will return an integer, given a string representation of number as input.

|  So here we validate that the '''age field''' contains a valid positive integer.

| If the validation fails, then we add error message to '''errorMsgs list'''

|  The age must be a positive integer.

|  Similarly, we have to validate that all the other fields too have valid data.

|  If the errorMsgs list is not empty, then we will display the '''errorMsgs '''on '''addUser '''''dot '''''jsp''' itself

|  Now, let us come to the '''addUser '''''dot '''''jsp.'''

|  Here also, first we have imported '''User '''''dot '''''java.'''

|  Inside the '''scriptlet tags '''we have created an '''object '''of type '''User.'''

|  We check if this value is equal to '''null.'''

|  If it is not equal to null, then  we display the error message just as we had done for '''index ''' '''dot''' '''jsp.'''

|  If not, we will get the value of the '''attribute user from request '''using  '''User model.'''

|  The first field is '''First Name '''of '''input type '''as''' text ''','''name '''as '''firstName '''and '''value '''as '''user '''''dot '''''getFirstName.'''

|  Similarly you have to do for other fields.

|  We also have a  '''submit ''' button and value as  ''' Add User.'''

|  This is how we validate the fields in '''addUser.jsp.'''

|  You can try out different errors on the '''Add User page.'''

|  Now let us see that the user '''harshita''' has been added to the '''database.'''

| So come back to user table. We can see that '''harshita''' is added to the database.

| In this tutorial we have learnt:

|  '''Field validation'''

|  It summarizes the Spoken Tutorial Project

|  If you do not have good bandwidth you can download and watch it

|  The Spoken Tutorial Project Team

|  Conducts workshops using spoken tutorials

|  Gives certificates for those who pass an online test

|  For more details please write to contact at spoken hyphen tutorial dot org

|  Spoken Tutorial Project is a part of the Talk to a Teacher Project

|  It is supported by the National Mission on Education through ICT, MHRD, Government of India

|  The '''Library Management System''' has been contributed by a leading software MNC, through their Corporate Social Responsibility Programme.

| This is Arya Ratish from IIT Bombay signing off.