Java and J2EE is the most used technologies in enterprise web development. Telecom operators, service providers are using these technlogies; banking and insurance companies are moving to Java from old generation technologies. https://www.udemy.com/java-web-developmen-with-real-world-development-flow If you want to earn much in web development business, you also need to learn Java web technologies. Java has de facto standart frameworks such as EJB 3.0, Spring and others that can be bound to them. But at heart, they all use the similar JSP/Servlet technology and add some layers above them to speed up the development. You will use them in your daily business but before using them, you must learn the basics and what is going on while using them. Otherwise, you will not be able to find a proper solution to common problems. This course will make you understand the basics of JSP / servlet technlogies, designing a relational database, DB operations, design patterns, working with other developers, and let you know the must-do operations in professional projects such as performance increasing, logging errors. If you want to develop a web-site in a couple of hours without understanding what you are doing, you may go ahead and find other resources. But if you really want to understand what you are doing and learn the theory at the same time, this course will be a great oppurtunity for you. You will develop a real working project. Yow will first write quick and dirty code then you will apply professional patterns one by one while investigating the problems. You will walk through a real development flow: 1- Write a quick and dirty code for doing the job. 2- You will design database tables and high performance queries 3 - You will apply design patterns to make the code reusable and high performance. 4 - You will beautify the user interface with Javascript and CSS tweaks 5- You will add exception handling, logging mechanism for production environment 6- AT THIS STEP, YOU WILL BE HIRED FOR MUCH MUCH HIGHER SALARIES. BECAUSE YOU ARE A REAL PROFESSIONAL.

1. JSP and SERVLET
Creating Web Applications
by www.javathlon.com

2. www.javathlon.com
Client - Server Web Applications
CLIENT SERVER HTTP PROTOCOL
HTML PAGE PROCESS DATA AND
RESPOND WITH RESULT

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Client - Server Web Applications
CLIENT SERVER HTTP PROTOCOL
HTML PAGE PROCESS DATA AND
RESPOND WITH RESULT

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HTTP PROTOCOL
STANDART BEHAVIOURS
● GET method
Ask server for a resource via a URI
(HTML page, image, MP3 etc)
● POST method
Sent a web form to server and get a resource
● Other methods
HEAD, PUT, DELETE, TRACE

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Client - Server Web Applications
CLIENT SERVER HTTP PROTOCOL
HTML PAGE PROCESS DATA AND
RESPOND WITH RESULT

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Client - Server Web Applications
CLIENT HTTP PROTOCOL
JSP PAGE
PROCESSING UNIT
(SERVLET)
PROCESSING UNIT
(SERVLET)
SERVER
PROCESSING UNIT
(SERVLET)
DATABASE

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NEED FOR APPLICATION SERVERS
● Dispatch requests
● Thread management
● Session management
● Caching and object pooling
We will use APACHE TOMCAT

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Reminders
How a J2EE project runs?
● Client side consists of JSP pages.
A JSP is an HTML page with special tags to get
or send dynamic data from/to server.
● Servlets carry business code on server side
and redirects the client to proper pages as
result.
● JSPs and servlets communicate via HTTP
protocol. Mostly GET and POST methods.

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Reminders
How a J2EE project runs?
JSP and servlets are contained in web
application servers ( servlet containers) such
as Apache Tomcat.
We develop configuration files such as web.
xml to regulate interactions among JSPs,
servlets and other resources.

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TECHNOLOGY STACK
Programming IDE Servlet Container
(Application server)
Java Runtime Environment 6

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SERVLET MECHANISM
SERVLET
Http Servlet Request
Return an HTML content
Return a multimedia file
Redirect the client to a page
Forward request to another servlet
Get or Post Method

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HTTPSERVLETREQUEST
GET method
POST method
SERVLET
When you enter a web address to a web browser, it requests the
resource by GET method.
The request body is limited to about 250 characters.
Sample:https://www.google.com.tr/?q=java&safe=off&output=search
You need to send a web form for using POST method. The request body
is limitless

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HTTPSERVLETRESPONSE
Talha Ocakci
Return an HTML content
Return a multimedia file
Navigate the client to another page
Forward request to another servlet
SERVLET
Request
Content-Type: text/html
Use: PrintWriter object of HTTPServletResponse
Content-Type: application/pdf, image/jpeg...
Use: OutputStream object of HTTPServletResponse
Content-Type: none
Use: sendRedirect() method
Content-Type: none
Use: RequestDispatcher object of ServletContext

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HTTPSERVLETRESPONSE
Return an HTML content
Return a multimedia file
Navigate the client to another page
Forward request to another servlet
SERVLET
Request
Content-Type: text/html
Use: PrintWriter object of HTTPServletResponse
Content-Type: application/pdf, image/jpeg...
Use: OutputStream object of HTTPServletResponse
Content-Type: none
Use: sendRedirect() method
Content-Type: none
Use: RequestDispatcher object of ServletContext

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SCRIPTLET in JSP
A scriptlet is a piece of Java-code embedded in the HTML.
The scriptlet is everything inside the <% %> tags.
Between these the user can add any valid Scriplet i.e. any
valid Java Code.

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IMPLICIT OBJECTS in JSP
They are the objects that you can use inside scriptlets
application javax.servlet.ServletContext
out javax.servlet.jsp.JspWriter
request javax.servlet.ServletRequest
response javax.servlet.ServletResponse
session javax.servlet.http.HttpSession
page java.lang.Object
servletconfig javax.servlet.ServletConfig

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OBJECT SCOPES
in SERVLETCONTEXT
Application Scope
Request
Scope
Session scope

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HTTP SESSION OBJECT
SESSION ID
Session object
Attribute map
name1 value1
name2 value2

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HTTPSERVLETRESPONSE
Talha Ocakci
Return an HTML content
Return a multimedia file
Navigate the client to another page
Forward request to another servlet
SERVLET
Request
Content-Type: text/html
Use: PrintWriter object of HTTPServletResponse
Content-Type: application/pdf, image/jpeg...
Use: OutputStream object of HTTPServletResponse
Content-Type: none
Use: sendRedirect() method
Content-Type: none
Use: RequestDispatcher object of ServletContext

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REDIRECTING REQUEST
Request forwarding and redirection are different
concepts.
When you forward a request, request and response
objects are transferred. Url stays the same.
When you redirect the request to another
JSP/servlet, request and response objects are not
transferred to new object. URL changes to the
directory of new page.

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Tip for being a wanted J2EE
developer
● Avoid using JAVA code inside a JSP file. Use
JSP directives and JSP actions instead.
● Avoid using HTML code inside a servlet.
Instead, use HTML code in JSP page and
pass values it from the servlet.

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JSP Actions
● jsp:useBean
Searches for an objects inside the given scope
● jsp:getProperty
● jsp:setProperty
Gets/sets a value of a given object

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jsp:useBean action
<jsp:useBean
id="memberInfo"
class="com.qapro.register.MemberInfo"
scope="request">
</jsp:useBean>
request.getParameter(“memberInfo”)
<jsp:useBean
id="memberInfo"
class="com.qapro.register.MemberInfo
scope="session">
</jsp:useBean>
request.getSession().getParameter(“memberInfo”)
<jsp:useBean
id="memberInfo"
class="com.qapro.register.MemberInf
scope="application">
</jsp:useBean>
ServletContext sc = getServletContext();
sc.getAttribute(“memberInfo”)

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jsp:getProperty and jsp:setProperty
Gets/sets an attribute of an
object with a given id

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JSTL BASICS
Java Server Tag Library
Provides shorthand notation to access:
● Attributes of standard servlet objects
● Bean properties
We use them, because writing JAVA code
inside JSP is not a good practice. It is a third
party library of Apache Foundation.

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JSTL and JAVA Code Relation
Iterating over a list
JAVA NOTATION
<ul>
<%
for(int i=0; i<messages.length; i++) {
String message = messages[i];
%>
<li><%= message %></li>
<% } %>
</ul>
JSTL NOTATION
<ul>
<c:forEach var="message” items="${messages}">
<li>${message}</li>
</c:forEach>
</li>

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FULL LIST OF JSTL TAGS

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CLUE
WEB APPLICATION
WEB BROWSER
ask for sth
show result

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CLUE
A basic web application is nothing more than a system that populates data
from a database, insert into it, modify the data and visualize it.
USER INTERFACE DATABASE
WEB APPLICATION
sends input
select
delete &
update
insert
shows result

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WORKING WITH DATABASE
Description
A database is any file or
file system that you can
● store your data
● manipulate data
● search for a desired
item

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WORKING WITH DATABASE
Database Types
● Flat files (text or binary)
● Flat file systems
● Non - relational databases (eg. MongoDB)
● Relational databases (eg. MySQL)

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WORKING WITH DATABASE
Why use RDBMS?
Relational Database
Systems:
Ease your tasks for
quickly inserting,
updating, querying,
deleting the data you
have on your hands
using SQL.

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WORKING WITH DATABASE
Relational Databases
Relational Database Systems:
Stores the data in tables and relations between
those tables.

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WORKING WITH DATABASE
Relational Database Structure
Table: A real world or imaginary entity model
that has attributes. (A user metadata)
Row: An instance of a entity model (A user
instance)
Column: Attribute of an entity (User’s name)
Primary key: Identifier of a instance (User’s
id)
Foreign key: Dependency of an entity to
another entity (Reference to user’s question)

35. WORKING WITH RELATIONAL www.javathlon.com
DATABASES
First example - Tables and columns
Keep track of all money transfers in a bank. You need to store this data permanently.
ROW 1 ROW 2
Sender name John
Sender surname Lennon
Sender account no 79879878978
Receiver name Paul
Receiver surname McCartney
Receiver account no 12121212121
Amount 300
Currency USD
Date 1.1.2014
Sender name Kirk
Sender surname Hammett
Sender account no 565656565
Receiver name James
Receiver surname Hetfield
Receiver account no 808080801
Amount 50000
Currency USD
Date 3.1.2014
attribute value
DB TABLE (MONEY TRANSFER)

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SQL
(Structured Query Language)
● DDL (Data Definition Language)
Used to create or modify tables, data types of
columns
● DML (Data Manipulation Language)
Used to insert, update, delete data and query
for desired data

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DATA TYPES
● String types
● Numeric types
● Date & Time types
● Binary objects

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WORKING WITH RELATIONAL
DATABASES
Creating table structures
Done with DDL (Data Definition Language )
CREATE TABLE money_transfer(
transfer_id INTEGER PRIMARY KEY,
sender_name VARCHAR(50) NULL,
sender_surname VARCHAR(50) NULL,
sender_surname VARCHAR(50) NULL,
sender_account_no VARCHAR(20) NULL,
receiver_name VARCHAR(50) NULL,
receiver_surname VARCHAR(50) NULL,
receiver_account_no VARCHAR(50) NULL,
amount FLOAT;
currenct VARCHAR(4) NULL,
transfer_date DATE NULL
);
Sender name John
Sender surname Lennon
Sender account no 79879878978
Receiver name Paul
Receiver surname McCartney
Receiver account no 12121212121
Amount 300
Currency USD
Transfer Date 1.1.2014

39. WORKING WITH RELATIONAL www.javathlon.com
DATABASES
First example - Breaking the data into smaller units
Multiple similar records means lots of repetition and repetition means mess.
For preventing the repetition, we break the data into multiple columns.
Sender name John
Sender surname Lennon
Sender account no 79879878978
Receiver name Paul
Receiver surname McCartney
Receiver account no 12121212121
Amount 300
Currency USD
Date 1.1.2014
Sender name John
Sender surname Lennon
Sender account no 79879878978
Receiver name George
Receiver surname Harrison
Receiver account no 12045872
Amount 400
Currency USD
Date 1.2.2014
Sender name John
Sender surname Lennon
Sender account no 79879878978
Receiver name Ringo
Receiver surname Start
Receiver account no 13698985
Amount 500
Currency USD
Date 1.3.2014

40. WORKING WITH RELATIONAL www.javathlon.com
DATABASES
First example - Data normalization
● Basic client data is extracted from the money transfer information.
● Client data is stored in another table. Identifier of the record inside client table is
referenced from money transfer table
Sender Client data
121
Receiver name George
Receiver surname Harrison
Receiver account no 12045872
Amount 400
Currency USD
Date 1.2.2014
Sender Client data
121
Receiver name Ringo
Receiver surname Starr
Receiver account no 13698985
Amount 500
Currency USD
Date 1.3.2014
Client data
Client id 121
Client name John
Client surname Lennon
Client account no 79879878978
Client id( Foreign key)

41. www.javathlon.com Tip for being a wanted J2EE
developer
A database table
SHOULD correspond
to at least one real
world or virtual entity.
DATABASE TABLE DESIGN PRINCIPLES
1

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Tip for being a wanted J2EE
developer
2
Dependent entities
should reference to the
owner entity for data
integration.
DATABASE TABLE DESIGN PRINCIPLES

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DATABASE DESIGN
for the
USER MANAGEMENT
MODULE
of
QA PLATFORM

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REGISTRATION
Insert a user with
● username,
● password
● and other personal details.

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AUTHENTICATION
Check if given username-password pair exists
in database.

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REGISTRATION
DB SCHEMA
STANDART MUST-DOs
1. Put a primary key.
2. Put insertion date,
3. Put active/passive bit
BUSINESS SPECIFIC
1. Store username and
password
2. Store personal details

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REGISTRATION
CREATE TABLE
CREATE TABLE `user` (
`user_id` int(11) NOT NULL,
`user_name` varchar(45) DEFAULT NULL,
`password` varchar(45) COLLATE DEFAULT
NULL,
`is_active` bit(1) DEFAULT NULL,
`name` varchar(45) DEFAULT NULL,
`surname` varchar(45) DEFAULT NULL,
`insert_date` datetime DEFAULT NULL,
`role_name` varchar(45) DEFAULT NULL,
PRIMARY KEY (`user_id`)
)

48. A PRIMER FOR DATA MANIPULATwwIwO.javNath lon.com
with SQL
Insert data
INSERT INTO TABLENAME
(first_column,...last_column)
VALUES (first_value,...last_value);
INSERT INTO user
(user_id, user_name, password)
VALUES (1, 'paul_weller','hzf1234fddf')

49. A PRIMER FOR DATA MANIPULATwwIwO.javNath lon.com
with SQL
Primary key
insert into user (user_id, user_name, password) values(100,
'paul_weller','hzf1234fddf')
Error Code: 1062. Duplicate entry '100' for key 'PRIMARY' 0.000 sec
Each table HAS TO have a primary key. This lets your database vendor
to allocate unique space for each record in any tables.
insert into user ( user_name, password) values
('eddie_vedder','hzf1234fddf');
Each table HAS TO have a primary key. This lets your database vendor
to allocate unique space for each record in any tables.
You will see user_id column gets unique values one by one.

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A PRIMER FOR DATA MANIPULATION
with SQL
Update a record
update TABLENAME
set COLUMNNAME = VALUE
update user
set user_name= ‘hgklkg45784’

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A PRIMER FOR DATA RETRIEVAL
with SQL
Retrieve all records
DO NOT use * in select clauses.
Using * is a good example of cutting corners
that junior developers do.
Define which columns you exactly need and
want to populate.

52. A PRIMER FOR DATA RETRIEVAL wwwwi.jtavhath lon.com
SQL
Restrict records
select COLUMN1,COLUMN2
from TABLENAME
where COLUMN1 = VALUE
and/or COLUMN2 = VALUE2
select user_name from user
where user_name =’'paul_weller'’ and
password = ‘'hzf1234fddf'’

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IN NEXT CHAPTER
● Database Connections
● Transactions
● What is ACID?
● Committing and rolling the transactions
back
● DB Engine - Java communication

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DATABASE CONNECTIONS
Database connection is the means by which
a database server and its client software
communicate with each other.

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WHY WE NEED DATABASE
CONNECTIONS?
We send the commands to DB server and get the results
via an open DB connection.
DB SERVER
Java web
application DB CONNECTION

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COMMUNICATION BETWEEN JAVA
AND DATABASE
Database talks
SQL, but Java does
not know how to
talk in SQL, it
needs a translator
called JDBC (Java
Database
Connector).

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DB CONNECTION POOLS
DB connection opening and closing is so
expensive operations compared to execute
basic queries.
Instead of open/close a connection for each
query, create a bunch of connections* and use
them over and over again.
* = Connection pool

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DB CONNECTION POOL USAGE

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CONNECTION POOL
Implementations in Java
● C3P0
● BoneCP
...

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DATABASE TRANSACTIONS
A unit of work performed within a database
management system against a database.

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DATABASE TRANSACTIONS
ALL OR NOTHING PRINCIPLE
1. Open connection
2. Begin transaction
3. Debit $100 to Groceries Expense Account
4. Credit $100 to Checking Account
5. Commit transaction
6. Close connection
TRANSACTION

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ACID
Properties that a transaction must have
Atomicity:
Based on “all or nothing” principle
All statements succeed or all fail in case of
any power failures, errors, and crashes.

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ACID
Properties that a transaction must have
Consistency:
If, for some reason (eq: programming error), a
transaction is executed that violates the
database’s consistency rules, the entire
transaction will be rolled back and the
database will be restored to a state consistent
with those rules.
eq: NULL inserting to a not-nullable column

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ACID
Properties that a transaction must have
Isolation:
Before committing a transaction,
modifications should not be visible to another
transaction.

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ACID
Properties that a transaction must have
Durability:
Durability guarantees that the database will
keep track of pending changes in such a way
that the server can recover from an abnormal
termination.

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DATABASE DESIGN
for the
USER ROLE
MANAGEMENT MODULE

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User Role- Permissions Logic
MODERATOR
MODIFY POST DELETE POST CREATE POST
USER 1
USER 2

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User Role- Permissions
Logic
Required permissions:
1- Deleting posts
2- Correcting posts
Required permissions:
1- Accepting new users
2- Deleting users
John Hopkins is
a moderator.
A moderator has
permissions for
1- Deleting posts
2- Correcting
posts

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Tip for being a wanted J2EE
developer
Why not assign the permissions directly to the
user but assign to a role?
Because adding or removing the permissions to a
role, lets the system grant or revoke this
permission from all the users who belong to this
role.
Otherwise you would execute this modification
on all users and this means a huge cost.

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Requirements:
● TABLE RELATIONS
(1 to MANY, MANY to 1, MANY to MANY)
● SQL JOINS
(inner join, left join, right join, full join,
self join)

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THE MEANING OF RELATIONAL
in RELATIONAL DATABASES
One object may belong to how many other
owner objects?
One object may own to how many other
dependent objects?

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TABLE RELATIONS
ONE TO ONE
USER USER-DETAILS
(Country, Height, Weight ...)
If you safely can add the columns in one
table to another relation means 1-1.

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TABLE RELATIONS
ONE TO ONE
OPTION 1
USER TABLE
USER ID USER NAME COUNTRY REGISTRATION
DATE
HEIGHT WEIGHT TIMEZONE
USER TABLE
USER ID USER NAME REGISTRATION
DATE
USER DETAILS TABLE
USER ID HEIGHT WEIGHT COUNTRY
OPTION 2

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TABLE RELATIONS
ONE TO MANY
ONE MANY
QUESTION ANSWER 1
● A question may own two answers.
● But, an answer can not be given two
multiple questions.
ANSWER 2
QUESTION ANSWER 3

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TABLE RELATIONS
MANY TO MANY
MANY MANY
USER TOPIC 1
● A user may follow multiple topics
● A topic may be followed by multiple
users.
TOPIC 2
USER TOPIC 3

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TABLE RELATIONS
MANY TO MANY
USER TABLE
USER ID USER NAME USER NICKNAME
1 Talha Ocakçı talhaocakci
2 James Dio dio
TOPIC TABLE
TOPIC ID TOPIC NAME
1 Geography
2 History
USER FOLLOWED TOPICS
USER ID TOPIC ID FOLLOW TIME
1 1 10.06.2014
2 1 18.06.2014
2 2 18.07.2014

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JOINING TABLES
To retrieve and combine different attributes of
an entity from several tables.
SELECT CLAUSE +
FROM CLAUSE +
JOIN CLAUSE (multiple) +
WHERE CLAUSE +

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JOINING TABLES
Inner Join
Both tables must have the same value on
joined columns.
eq. Populate list of permissions that a user
has.

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JOINING TABLES
Left (Outer) Join
If a row in table 1 does not have a match in
table 2, it still exists in result set.

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81. IMPLEMENTING
JAVA WEB APPLICATION

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WHAT WE WILL DO?
1. Without caring of user interface design,
focus on the technical details.
2. Find the most time consuming phases in
development and ease them professionally

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REGISTER USER
Get username, email,
name, surname of user
and post it to servlet
JSP
1. Get values from request
2. Get DB connection
(Create or get one from DB
connection pool)
3. Start transaction
4. Insert user to DB
5. Release all resources
6. Put message into
response
6. Redirect to another
page
SERVLET
Show the
message inside
JSP

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JDBC CLASSES
Statement
● Contains a static SQL statement
● Not reusable
PreparedStatement:
● Contains precompiled SQL statement.
● Used to efficiently execute this statement
multiple times by just setting parameters.

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JDBC CLASSES
ResultSet
Holds the database result row by row
Holds the metadata of the DB result (count,
column names, etc)

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JAVA - MYSQL TYPE
CORRESPONDENCE

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RESULT SET OBJECT
VALUES METADATA
talha ocakci talhaocakci
paul auster paulauster
... ... ...
Count
Column
types
Schema
name
Table name
...
POINTER

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RESULT SET OBJECT
resultset.next() method moves the pointer to next row.
If reaches to the end it returns false.
talha ocakci talhaocakci
paul auster paulauster
... ... ...
POINTER
Initially, it points to the very beginning of the ResultSet
object but not the first row. To get the first row, you
need to invoke next() before iterating.

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REGISTER USER
Get username, email,
name, surname of user
and post it to servlet
JSP
1. Get values from request
2. Get DB connection
(Create or get one from DB
connection pool)
3. Start transaction
4. Insert user to DB
5. Release all resources
6. Put message into
response
6. Redirect to another
page
SERVLET
Show the
message inside
JSP

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CONNECTION POOLS
Created on servlet containers (Tomcat 7) or
application servers (JBOSS, Glassfish, etc..)
and can be access by JNDI
Created with C3P0 independent from a servlet
container or an application server.

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CONNECTION POOLS
Configuration
Min connection size: Whatever happens,
connection number will not drop below this.
Max connection: Number of connection can
not exceed this number.
Timeout: If idle time of a connection exceeds
this time, it returns back to pool
automatically.

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INITIALIZE RESOURCE WHILE
BOOTSTRAPPING
● Mark your servlet for automatic invoking
while bootstrapping the application in
deployment descriptor.
marker: load-on-startup tag.
● Initialize resources in init() method of
servlet.

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EMAIL VALIDATION
1- Insert the new user record to user table
2- Insert a related record to email-validation
table including user id and validation code.
3- Email the validation url including the
validation code to user’s email.
4- When sent link is clicked, check the
validation code in url against the one in DB.

94. www.javathlon.com
EMAIL VALIDATION
When a connection is created, it is in
auto-commit mode.
The way to allow two or more
statements to be grouped into a
transaction is to disable the auto-commit
mode.

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GET GENERATED KEYS
preparedStatement.getGeneratedKeys()
returns a Result Set with one column and
one row:
POINTER
VALUES
29

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WORKING IN PROFESSIONAL
SOFTWARE DEVELOPMENT TEAMS

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WORKING IN A TEAM
If team members use;
● Different approaches to similar problems
● Different relations between software
layers...
There will be chaos later on.

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WORKING IN PROFESSIONAL
SOFTWARE DEVELOPMENT TEAMS
Why do we use design patterns?
Developers agree on the best solutions and
apply them for similar problems.

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SOFTWARE ARCHITECTURE AND
DESIGN PATTERNS
Design patterns
ensure the project
will not fail by the
time passing. If you
don’t obey the
rules, the failure
underneath will be
observed.

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DESIGN PATTERN and STRATEGY
Design Pattern: Describes a solution to a
common problem in a context.
Strategy: The real implementation of the
pattern

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EXAMPLES in SOFTWARE
ENGINEERING
Problem: I create huge objects over and
over again, so project consumes so much
memory.
Solution: Use a single instance
and reuse it whenever possible.
Pattern: Singleton pattern
Meaning: Create one and use it over and
over.
Example: Our DB connection pool

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EXAMPLES in SOFTWARE
ENGINEERING
Problem: I have too many controllers
(servlets), so I lost the control of
redirecting the requests.
Solution: Use a common class to
redirect all requests so that you can
manage in just one place.
Pattern: Front controller pattern
Example: DispatcherServlet in Spring
framework

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EXAMPLES in SOFTWARE
ENGINEERING
Problem: I forgot to release
the resources after DB
operations and I don’t want to
copy and paste the same code
to everywhere.
Solution: Move the
boilerplate code to another
common class.
Pattern: Template pattern
Example: We will implement
now.

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BIG PICTURE of DESIGN PATTERNS
1. Creational Patterns
a) Singleton
b) Factory
c) Prototype
d) Builder
2. Behavioural Patterns
a) Template
b) Mediator
3. J2EE Patterns
a) Front Controller
b) DAO Pattern
c) Model View Controller
d) View Helper
and so on...

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BIG PICTURE of DESIGN PATTERNS

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CORRECT USAGE DOSE of PATTERNS

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IMPLEMENT TEMPLATE PATTERN
Why we need them?
1- You will possibly forget common operations
like closing DB connection, Prepared
Statement and ResultSet.
2- You will repeatedly copy tens of lines of
initialization, resource cleaning code for
simple queries.

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IMPLEMENT TEMPLATE PATTERN
A class extends an abstract class that do the boilerplate things
Concrete class Abstract class
1. Resource allocating
2. Execute DB operations
Populate Result Set
3. Resource releasing
Get DB Connection
Create PreparedStatement
Start transaction
Commit transaction
Close connection
Close PreparedStatement
Close ResultSet

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DATA ACCESS OBJECT PATTERN
Problem:
1- You should separate business and DB operations.
In service layer, you should just deal with business.
Not with DB specific ugly code, connections, etc.
2- You need a real entity object but not a
collection of low level strings, numbers, booleans…
3- You need to run unit tests.

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DATA ACCESS OBJECT PATTERN
VIEW
LAYER
(Shows
model’s
attributes)
SERVICE
LAYER
(Combines multiple
DAOs if required)
DB LAYER
(DAO)
Each class deal
with just one DB
table
MODEL REAL
ENTITY
Get result set, place basic
values
into entity instances.

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RELATION between DAO and
TEMPLATE PATTERNS
VIEW CONTROLLER
DB LAYER
MODEL (DAO) REAL
ENTITY
TEMPLATE
PATTERN
USED BY
Get result set, place basic values
into entity instances.
Might be the same type of object or two separate
object types that may adapted to each other

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● DAO Connection Scoping
○ Method Scope
○ Instance Scope
○ Thread Scope

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UNIT TESTING DAO LAYER
Unit testing means executing a method
without an application server.
1- Using JUnit
2- (Fake unit testing) Simply by using an main
class.

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BEFORE AJAX

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AFTER AJAX (Async Javascript & XML)

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XMLHttpRequest object
Provides the ability to
1- Send asynchronous requests to the server
side.
2- Be noticed in each step of the flow (request
sent, headers received, loading, done, error
occurred)

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XMLHttpRequest object

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XXMMLLHHtttptRpeRqueeqsut eobsjte cotb mjeecthto mdsethods
open(method, url)
Ex: open(“POST”, “Voting”)
setRequestHeader(name, value)
Ex: setRequestHeader("Content-type",
"application/x-www-form-urlencoded")
send(data)
Ex: send(“questionId=1&type=UP”)

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XXMMLLHHtttptRpeRqueeqsut eobsjte c- tr meeatdhyoSdstate
Shows the internal state of the XMLHttpRequest instance.
When it is switched to another state, you are informed via
a readyStateChangeEvent. You can update your HTML
page accordingly.
STATE NUMERIC
VALUE
DESCRIPTION
UNSENT 0 The object has been constructed.
OPENED 1 The open() method has been successfully invoked
HEADERS_RECEIVED 2 All redirects (if any) have been followed and all HTTP headers of
the final response have been received. Several response
members of the object are now available.
LOADING 3 The response entity body is being received.
DONE 4 The data transfer has been completed or something went wrong
during the transfer

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Communicate with XMLHttpRequest
Event name Interface Dispatched when…
readystatechange Event The readyState attribute changes value, except when it changes to
UNSENT.
loadstart ProgressEvent The request starts.
progress ProgressEvent Transmitting data.
abort ProgressEvent The request has been aborted. For instance, by invoking the abort()
method.
error ProgressEvent The request has failed.
load ProgressEvent The request has successfully completed.
timeout ProgressEvent The author specified timeout has passed before the request
completed.
loadend ProgressEvent The request has completed (either in success or failure).

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XMLHttpRequest
Status codes
CODE STATUS
200 SUCCESSFUL
301 MOVED PERMANENTLY
403 FORBIDDEN
404 NOT FOUND

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XMLHttpRequest
Handling Successful State
Successful state means
● readyState = 4
● status = 200

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SUCCESSFUL AJAX FLOW
HTML PAGE
XMLHttpRequest
instance Server
Create
Open
Send
readyStateChange:1
readyStateChange:2
process
readyStateChange:3
status : 200
readyStateChange:4
status : 200
Manipulate the
HTML
send data to server
send result (JSON, string)
onReadyStateChange
event

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AJAX CALL FLOW
● Create an XMLHttpRequest instance.
● Configure the url and method
● Send data
● Obtain and parse the result
● Manipulate your HTML page accordingly.

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