Java/Servlet/JSP/JDBC

INTRODUCTION TO JAVA
SERVLET
JSP(JAVA SERVER PAGE)
DATA BASE CONNECTION

HISTORY
 Java is a programming language created by James
Gosling from Sun Microsystems (Sun) in 1991.
 Java is a high-level programming language. Its a
platform independent.
 Java language is called as an Object-Oriented
Programming language

WHY JAVA
 It’s the current “hot” language
 It’s almost entirely object-oriented
 It’s more platform independent
 It’s more secure

WHERE IT IS USED?
Desktop Applications such as acrobat reader,
media player, antivirus etc.
Web Applications
Enterprise Applications such as banking
applications.
Mobile
Embedded System
Smart Card
Robotics
Games etc.

JAVA FEATURES
 Compiled and Interpreted
 Platform Independent and portable
 Object-oriented
 Robust and secure
 Distributed
 Familiar, simple and small
 Multithreaded and Interactive

DIFFERENT PROGRAMMING PARADIGMS
 Functional/procedural programming:
• program is a list of instructions to the
computer
 Object-oriented programming
• program is composed of a collection objects
that communicate with each other

MAIN CONCEPTS
1. Objects.
2. Classes.
3. Data Abstraction.
4. Data Encapsulation.
5. Inheritance.
6. Polymorphism.

JVM
JVM stands for
Java Virtual Machine
The Java runtime employs a garbage
collection to reclaim the memory occupied by
on object.

machine code
OS/Hardware
myprog.c
C source code
gcc
myprog.exe
Platform Dependent
bytecode
JVM
myprog.java
Java source code
javac
myprog.class
OS/Hardware
Platform Independent

What is JVM?
 A specification where working of Java Virtual
Machine is specified. But implementation
provider is independent to choose the algorithm.
Its implementation has been provided by Sun
and other companies.
 An implementation Its implementation is
known as JRE (Java Runtime Environment).
 Runtime Instance Whenever you write java
command on the command prompt to run the
java class, and instance of JVM is created.

What it does?
The JVM performs following operation:
 Loads code
 Verifies code
 Executes code
 Provides runtime environment
JVM provides definitions for the:
 Memory area
 Class file format
 Register set
 Garbage-collected heap
 Fatal error reporting etc.

JAVA KEYWORDS
Abstract,const,finally,int,public,this,boolean,cont
inue,float
interface,return,throw,break,default,for,long,shor
t,throws
byte,do,goto,native,static,transient,case,double,if
,new,strictfp
try,catch,else,implements,package,super,void,cha
r,extends
import,private,switch,volatile,class,final,instance
of,protected
synchronized,while

PRIMITIVE TYPES
 int 4 bytes
 short 2 bytes
 long 8 bytes
 Byte 1 byte
 Float 4 bytes
 double 8 bytes
 char Unicode encoding (2 bytes)
 boolean {true, false}
Behaviors is
exactly as in C++
Note:
Primitive type
always begin
with lower-case

CONTROL STATEMENTS
Java control statements cause the flow of
execution to advance and branch based on the
changes to the state of the program.
Control statements are divided into three groups:
1) selection statements allow the
program to choose different parts of the execution
based on the outcome of an expression
2) iteration statements enable program
execution to repeat one or more statements
3) jump statements enable your program
to execute in a non-linear fashion

FLOW CONTROL
if/else
do/while
for
switch
If(x==4) {
// act1
} else {
// act2
}
int i=5;
do {
// act1
i--;
} while(i!=0);
int j;
for(int i=0;i<=9;i++)
{
j+=i;
}
char c=IN.getChar();
switch(c) {
case ‘a’:
case ‘b’:
// act1
break;
default:
// act2
}

ACCESS CONTROL
 public member (function/data)
• Can be called/modified from outside.
 protected
• Can be called/modified from derived classes
 private
• Can be called/modified only from the current
class
 default ( if no access modifier stated )
• Usually referred to as “Friendly”.
• Can be called/modified/instantiated from the
same package.

ARRAYS
 An array is used to store a collection of data, but
it is often more useful to think of an array as a
collection of variables of the same type.
 Arrays are:
1) declared
2) Created

EXAMPLE
 Declaration:
double[] myList;
 Creating Arrays:
double[] myList = new double[10];
↓[Array Index]

THREAD
Thread is a lightweight process that executes
some task.
Java is a multithreaded programming language.
Multithreading refers to two or more tasks
executing concurrently within a single program.
Every thread in Java is created and controlled by
the java.lang.Thread class.

BENEFITS OF THREADS
Threads are lightweight compared to processes,
it takes less time and resource to create a thread.
less expensive.
Thread intercommunication is relatively easy
than process communication.

EXCEPTIONS HANDLING
An exception is a problem that arises during the
execution of a program. An exception can occur
for many different reasons, including the
following:
• A user has entered invalid data.
• A file that needs to be opened
cannot be found.
• A network connection has been lost
in the middle of communications or
the JVM has run out of memory.

EXCEPTIONS HANDLING (CONT)
 Three categories of exceptions:
• Checked exceptions
• Runtime exceptions
• Errors
Exception Handling Keywords
• throw
• throws
• try-catch
• finally

 Runtime exceptions: A runtime exception is an
exception that occurs that probably could have been
avoided by the programmer. As opposed to checked
exceptions, runtime exceptions are ignored at the time of
compilation.

ABSTRACTWINDOWING
TOOLKIT (AWT):

Abstract Windowing Toolkit (AWT) is used for
GUI programming in java.
Computer users today expect to interact with
their computers using a graphical user interface
(GUI).
There are two basic types of GUI program in
Java:
• stand-alone applications
• applets.

Commonly used Methods of Component
class:
1)public void add(Component c)
2)public void setSize(int width , int height)
3)public void setLayout(LayoutManager m)
4)public void setVisible(boolean)

Example:
import java.awt.*;
class First extends Frame{
First(){
Button b=new Button("click me");
b.setBounds(30,100,80,30);// setting button position
add(b);//adding button into frame
setSize(300,300);//frame size 300 width and 300 height
setLayout(null);//no layout now bydefault BorderLayout
setVisible(true);//now frame willbe visible, bydefault not v
isible
}
public static void main(String args[]){
First f=new First();
}
}

SWING COMPONENTS
 Swing is a collection of libraries that contains
primitive widgets or controls used for designing
Graphical User Interfaces (GUIs).
 Commonly used classes in javax.swing package:
• JButton, JTextBox, JTextArea, JPanel,
JFrame, JMenu, JSlider, JLabel, JIcon, …
• There are many, many such classes to do
anything imaginable with GUIs

Each component is a Java class with a fairly extensive
inheritency hierarchy:

Using Swing Components
 Very simple, just create object from appropriate class –
examples:
• JButton but = new JButton();
• JTextField text = new JTextField();
• JTextArea text = new JTextArea();
• JLabel lab = new JLabel();
Adding components
Once a component is created, it can be added to a
container by calling the container’s add method:
• Container cp = getContentPane();
• cp.add(new JButton(“cancel”));
• cp.add(new JButton(“go”));

APPLET
Applet is a special type of program that is embedded in
the webpage to generate the dynamic content. It runs
inside the browser and works at client side.
Advantage of Applet
 It works at client side so less response time.
Secured
 It can be executed by browsers running
under many plateforms, including Linux,
Windows, Mac Os etc.
Drawback of Applet
 Plugin is required at client browser to
execute applet.

LIFECYCLE OF AN APPLET:
 Applet is initialized.
 Applet is started.
 Applet is painted.
 Applet is stopped.
 Applet is destroyed.
public void paint(Graphics g): is used to paint
the Applet. It provides Graphics class object that
can be used for drawing oval, rectangle, arc etc.

SIMPLE EXAMPLE OFAPPLET
//First.java
import java.applet.Applet;
import java.awt.Graphics;
public class First extends Applet{
public void paint(Graphics g){
g.drawString("welcome to applet",150,150);
}
}
/*
<applet code="First.class" width="300" height="300">
</applet>
*/

SERVLET
 Servlet technology is used to create web application.
 Servlet technology is robust and scalable as it uses the
java language. Before Servlet, CGI (Common Gateway
Interface) scripting language was used as a server-side
programming language. But there were many disadvantages
of this technology.
Disadvantages of CGI
 If number of clients increases, it takes more time for
sending response.
 For each request, it starts a process and Web server is
limited to start processes.
 It uses platform dependent language e.g. C, C++, perl.

CGI(Commmon Gateway Interface)

Advantage of Servlet
 better performance: because it creates a thread for
each request not process.
 Portability: because it uses java language.
 Robust: Servlets are managed by JVM so no need
to worry about momory leak, garbage collection etc.
 Secure: because it uses java language..

Life Cycle of a Servlet (Servlet Life Cycle)
The web container maintains the life cycle of a servlet instance.
Let's see the life cycle of the servlet:
 Servlet class is loaded.
 Servlet instance is created.
 init method is invoked.
 service method is invoked.
 destroy method is invoked.

Servlet API
The javax.servlet and javax.servlet.http packages represent interfaces
and classes for servlet api.
Interfaces in javax.servlet package
There are many interfaces in javax.servlet package. They are as follows:
 Servlet
 ServletRequest
 ServletResponse
 RequestDispatcher
 ServletConfig
 ServletContext
 Filter
 FilterConfig
 FilterChain

ServletRequest Interface
An object of ServletRequest is used to provide the client request
information to a servlet such as content type, content length,
parameter names and values, header informations, attributes etc.
Methods of ServletRequest interface:
 public String getParameter(String name)
 public String[] getParameterValues(String name)
 java.util.Enumeration getParameterNames()
 public int getContentLength()
 public String getCharacterEncoding()
 public String getContentType()
 public ServletInputStream getInputStream() throws
IOException

RequestDispatcher in Servlet
The RequestDispacher interface provides the facility of
dispatching the request to another resource it may be html,
servlet or jsp. This interface can also be used to include the
content of another resource also. It is one of the way of servlet
collaboration.
Methods of RequestDispatcher interface
 public void forward(ServletRequest request,ServletResponse
response)throws ServletException,java.io.IOException
 public void include(ServletRequest request,ServletResponse
response)throws ServletException,java.io.IOException

Example of RequestDispatcher interface

SESSION TRACKING IN SERVLETS
 Session simply means a particular interval of time.
 Session Tracking is a way to maintain state (data) of an
user. It is also known as session management in servlet.
 Http protocol is a stateless so we need to maintain state
using session tracking techniques. Each time user
requests to the server, server treats the request as the new
request. So we need to maintain the state of an user to
recognize to particular user.

Session Tracking Techniques
There are four techniques used in Session tracking:
 Cookies
 Hidden Form Field
 URL Rewriting
 HttpSession

Cookies in Servlet
A cookie is a small piece of information that is persisted
between the multiple client requests.
A cookie has a name, a single value, and optional
attributes such as a comment, path and domain qualifiers,
a maximum age, and a version number.

Advantage of Cookies
 Simplest technique of maintaining the state.
 Cookies are maintained at client side.
Disadvantage of Cookies
 It will not work if cookie is disabled from the
browser.
 Only textual information can be set in Cookie
object.

Hidden Form Field
In case of Hidden Form Field a hidden (invisible) textfield is
used for maintaining the state of an user.
<input type="hidden" name="uname" value="Vimal Jaiswal">
Advantage of Hidden Form Field
 It will always work whether cookie is
disabled or not.
Disadvantage of Hidden Form Field:
 It is maintained at server side.
 Extra form submission is required on each pages.
 Only textual information can be used.

Example of using Hidden Form Field

URL Rewriting
 In URL rewriting, we append a token or identifier to the URL of
the next Servlet or the next resource. We can send parameter
name/value pairs using the following format:
url?name1=value1&name2=value2&??
 A name and a value is separated using an equal = sign,
a parameter name/value pair is separated from another
parameter using the ampersand(&).

Advantage of URL Rewriting
 It will always work whether cookie is
disabled or not (browser independent).
 Extra form submission is not required on
each pages.
Disadvantage of URL Rewriting
 It will work only with links.
 It can send Only textual information.

Example of using URL Rewriting

HttpSession interface
 In such case, container creates a session id for each user. The
container uses this id to identify the particular user. An object of
HttpSession can be used to perform two tasks:
 bind objects
 view and manipulate information about a session,
such as the session identifier, creation time, and
last accessed time.
 The HttpServletRequest interface provides two methods to get
the object of HttpSession:
 public HttpSession getSession()
 public HttpSession getSession(boolean create)

Event and Listener in Servlet
Events are basically occurrence of something. Changing the state
of an object is known as an event.
Event classes
The event classes are as follows:
 ServletRequestEvent
 ServletContextEvent
 ServletRequestAttributeEvent
 ServletContextAttributeEvent
 HttpSessionEvent
 HttpSessionBindingEvent

 JSP technology is used to create web application just like
Servlet technology.
 A JSP page consists of HTML tags and JSP tags.
 The jsp pages are easier to maintain than servlet because we
can separate designing and development.
 It provides some additional features such as Expression
Language, Custom Tag etc.
Advantage of JSP over Servlet
 Extension to Servlet
 Easy to maintain
 Fast Development: No need to recompile and
redeploy
 Less code than Servlet

JSP Scriptlet tag (Scripting elements)
 In JSP, java code can be written inside the jsp page using the
scriptlet tag.
Scripting elements
The scripting elements provides the ability to insert java code
inside the jsp. There are three types of scripting elements:
 scriptlet tag
 expression tag
 declaration tag
JSP scriptlet tag
A scriptlet tag is used to execute java source code in JSP. Syntax
is as follows:
<% java source code %>

JSP expression tag
 The code placed within expression tag is written to the output
stream of the response. So you need not write out.print() to write
data. It is mainly used to print the values of variable or method.
Syntax of JSP expression tag
<%= statement %>
JSP Declaration Tag
 The JSP declaration tag is used to declare fields and methods.
 The code written inside the jsp declaration tag is placed outside
the service() method of auto generated servlet.
Syntax of JSP declaration tag
<%! field or method declaration %>

JSP Implicit Objects
 These objects are created by the web container that are
available to all the jsp pages.
 A list of the 9 implicit objects is given below:
 out
 request
 response
 config
 application
 session
 pageContext
 page exception

Example of implicit object
Out:
<%out.print("Today"+java.util.Calendar.getInstance().getTime());
%>
Request:
<% String name=request.getParameter(“xxx"); %>
Response:
<% response.sendRedirect("http://www.google.com"); %>
Session:
<% session.setAttribute("user", xxx); %>
<% String name=(String)session.getAttribute("user"); ); %>
Exception:
<%@ page errorPage="error.jsp" %>
<%@ page isErrorPage="true" %>

JSP directives
 The jsp directives are messages that tells the web container how to
translate a JSP page into the corresponding servlet.
 There are three types of directives:
 page directive
 include directive
 taglib directive
Syntax of JSP Directive
<%@ directive attribute="value" %>
Attributes of JSP page directive
 import
 contentType
 isELIgnored
 Session
 errorPage
 isErrorPage

Jsp Include Directive
 The include directive is used to include the contents of any
resource it may be jsp file, html file or text file.
Advantage of Include directive
 Code Reusability
Syntax of include directive
<%@ include file="resourceName" %>
JSP Taglib directive
 The JSP taglib directive is used to define a tag library that
defines many tags. We use the TLD (Tag Library Descriptor) file
to define the tags.
Syntax JSP Taglib directive
<%@ taglib uri="uriofthetaglibrary" prefix="prefixoftaglibrary"
%>

Exception Handling in JSP
 The exception is normally an object that is thrown at runtime.
Exception Handling is the process to handle the runtime errors.
There may occur exception any time in your web application. So
handling exceptions is a safer side for the web developer. In JSP,
there are two ways to perform exception handling:
 By errorPage and isErrorPage attributes of page
directive
 By <error-page> element in web.xml file

Expression Language (EL) in JSP
 The Expression Language (EL) simplifies the accessibility of
data stored in the Java Bean component, and other objects like
request, session, application etc.
 There are many implicit objects, operators and reserve words in
EL.
Syntax for Expression Language (EL)
${ expression }
Implicit Objects in Expression Language (EL)
 pageScope
 requestScope
 sessionScope
 param

Simple example of Expression Language
<form action="process.jsp">
Enter Name:<input type="text" name="name“ >
<input type="submit" value="go"/>
</form>
process.jsp
Welcome, ${ param.name }

Custom Tag
 For creating any custom tag, we need to follow following steps:
 Create the Tag handler class and perform
action at the start or at the end of the tag.
 Create the Tag Library Descriptor (TLD) file
and define tags
 Create the JSP file that uses the Custom tag
defined in the TLD file

Understanding flow of custom tag in jsp

Create the Tag handler class
 To create the Tag Handler, we are inheriting the TagSupport
class and overriding its method doStartTag().To write data for
the jsp, we need to use the JspWriter class.
 The PageContext class provides getOut() method that returns
the instance of JspWriter class. TagSupport class provides
instance of pageContext bydefault.
public class MyTagHandler extends TagSupport
{
public int doStartTag() throws JspException
{
JspWriter out=pageContext.getOut();
}
}

Create the TLD file
 Tag Library Descriptor (TLD) file contains information of tag
and Tag Hander classes. It must be contained inside the WEB-INF
directory.
<taglib>
<tag>
<name>today</name>
<tag-class>com.javatpoint.sonoo.MyTagHandler</tag-class>
</tag>
</taglib>

Create the JSP file
 Let's use the tag in our jsp file. Here, we are specifying the path
of tld file directly.
 But it is recommended to use the uri name instead of full path
of tld file. We will learn about uri later.
 It uses taglib directive to use the tags defined in the tld file.
<%@ taglib uri="WEBINF/mytags.tld" prefix="m" %>
<m:today>Current Date and Time is: </m:today>

INTRODUCTION
Database Management System or DBMS in short, refers to the
technology of storing and retrieving users data with utmost
efficiency along with safety and security features.
DBMS allows its users to create their own databases which are
relevant with the nature of work they want. These databases are
highly configurable and offers bunch of options.

DATABASE
 A Database is a collection of related data organized in a
way that data can be easily accessed, managed and
updated.
 Any piece of information can be a data.
Ex: Name of a student, age, class and her subjects can
be counted as data for recording purposes.

OVERVIEW
 A DBMS is a software that allows creation, definition and
manipulation of database.
 DBMS is actually a tool used to perform any kind of operation
on data in database.
 DBMS also provides protection and security to database. It
maintains data consistency in case of multiple users.
 Here are some examples of popular dbms, MySql, Ms sql,
Oracle, Sybase, Microsoft Access and IBM DB2 etc.

ARCHITECTURE
Database architecture is logically divided into two types.
 Logical two-tier Client / Server architecture
 Logical three-tier Client / Server architecture

LOGICAL TWO-TIER CLIENT / SERVER
ARCHITECTURE
 The two-tier architecture is like
client server application. The
direct communication takes
place between client and server.
There is no intermediate
between client and server.
Advantages:
 Understanding and
maintenances is easier.
Disadvantages:
 Performance will be reduced
when there are more users.

LOGICAL THREE-TIER CLIENT / SERVER
ARCHITECTURE
Three tier architecture having
three layers.
1. Client layer
2. Business layer
3. Data layer

1. Client layer: Here we design the form using
textbox, label etc.
2. Business layer: It is the intermediate layer which has
the functions for client layer and it is used to make
communication faster between client and data layer. It
provides the business processes logic and the data
access.
3. Data layer: it has the database.
Advantages
o Easy to modify with out affecting other modules
o Fast communication
o Performance will be good in three tier architecture.

COMPONENTS OF DATABASE SYSTEM
 The database system can be divided into four
components.
1. Users
2. Database application
3. DBMS
4. Database

COMPONENTS OF DATABASE SYSTEM
 USERS: User may be of various types such as
DB administrator, system developer and end user.
 DATABASE APPLICATION: It may be personal,
Departmental, enterprise and Internal
 DBMS: Software that allow user to define, create and manages
database access. Ex, MySql, oracle, etc.
 DATABASE: Collection of logical data

FUNCTIONS
 Provides data Independence.
 Concurrency Control.
 Provide Recovery Services.
 Provides Utility Services.
 Provides a clear and logical view of the process.

ADVANTAGES
 Minimal data duplicity.
 Easy retrieval of data.
 Reduced development time and maintenance need.
 Minimal Data Redundancy.
 Data Consistency.
 Data Sharing.
 Better Controls.
 Reduced Maintenance

DISADVANTAGES
 Complexity
 Costly
 Large in size

RDBMS
 RDBMS stands for Relational Database Management
System. RDBMS is the basis for SQL, and for all
modern database systems like MS SQL Server, IBM
DB2, Oracle, MySQL, and Microsoft Access.

DATA DEFINITION LANGUAGE
 SQL uses the following set of commands to define database
schema:
 CREATE
 DROP
 ALTER
 TRUNCATE
 CREATE: Creates new databases, tables and views from
RDBMS
Create database dbms;
Create table article(id int , name varchar)
Create view for students;

 DROP: Drop commands deletes views, tables and
databases from RDBMS
Drop object type object name;
Drop database dbms;
Drop table article;
Drop view for_students;
 ALTER: Modifies database schema.
Alter object_type object_name parameters;
for example:
Alter table article add subject varchar;

DATAMANIPULATION LANGUAGE
 DML modifies the database instance by inserting,
updating and deleting its data.
 DML is responsible for all data modification in
databases.
 SQL contains the following set of command in DML
section:
 INSERT
 UPDATE
 DELETE
 SELECT

INSERT
 INSERT: Insert command is used to insert data into a table.
 Syntax:
INSERT into table_name values(data1,data2,…)

UPDATE
 The UPDATE statement is used to update records in a table.
Syntax
update table_name set column1=value1,column2=value2,...where
some_column=some_value;
 FOR EXAMPLE:
update Students set age=18 where s_id=102;

DELETE
 Delete command is used to delete data from a table.
 Delete command can use to delete a particular row or whole data in
the table.
 Syntax:
DELETE FROM table_name
WHERE some_column=some_value;
 To delete all row from a table.
DELETE FROM table_name;
or
DELETE * FROM table_name;

SELECT
 This command is used to select data from database.
 Syntax
SELECT column_name,column_name
FROM table_name;
and
SELECT * FROM table_name;

DATA CONTROL LANGUAGE (DCL)
 Data Control Language(DCL): Is a Structured query that allows
database administrators to configure security access to relational
databases.
 DCL commands are used to enforce database security in a multiple
user database environment.
 There are two types of DCL commands.
GRANT
REVOKE

GRANT
 SQL GRANT is a command used to provide access or privileges
on the database objects to the users.
The Syntax for the GRANT command is:
grant privilege_name on object_name
to {user_name |public|role_name}
[WITH GRANT OPTION];
 To allow a user to create a session.
grant create session to username

REVOKE
 The REVOKE command removes user access rights or
privileges to the database objects.
 The syntax for this command is defined as follows:
REVOKE [GRANT OPTION FOR] [permission] ON
[object] FROM [user]

KEY
• Key --> The attribute used to define a required item
 Types of keys:
* Primary Key: Key used to uniquely identify a record
* Foreign Key: A field in this table which is the Primary
key of another table

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Java/Servlet/JSP/JDBC