Advance Java Topics (J2EE)

INDEX
1.Brief Overview of Java
2.Advance java
3.Servlets
4.Session Handling
5.Database Handling
6.JSP
7.Struts
8.MVC
9.Tiles
10Hibernate

What is java?
Java is a computer programming language that
is concurrent, class-based, object-oriented.
 It is intended to let application developers "write once, run
anywhere" (WORA).
 Java applications are typically compiled to bytecode (class file)
that can run on any Java virtual machine (JVM) regardless
of computer architecture.
 Java is, as of 2014, one of the most popular programming
languages in use, particularly for client-server web
applications.
 Java is the Internet programming language

Java's History
• Java was originally developed by James Gosling at Sun
Microsystems (which has since merged into Oracle
Corporation).
• Originally named OAK in 1991
• First non commercial version in 1994
• Renamed and modified to Java in 1995 and released as a
core component of Sun Microsystems' Java platform.
• First Commercial version in late 1995
• Hot Java
-The first Java-enabled Web browser

Java Technology
• What is Java?
Java technology is both a programming
language and a platform.

--The Java Programming Language
The Java programming language is a high-level
language that can be characterized by all of the
following buzzwords:
-Simple
-Object oriented
-Distributed
-Multithreaded
-Dynamic
Architecture neutral
-Portable
-High performance
-Robust
-Secure

--The Java Platform
A platform is the hardware or software environment in
which a program runs. Some of the most popular platforms
are Microsoft Windows, Linux, Solaris OS, and Mac OS.
Most platforms can be described as a combination of the
operating system and underlying hardware. The Java
platform differs from most other platforms in that it's a
software-only platform that runs on top of other hardware-based
platforms.
The Java platform has two
components:
The Java
Virtual
Machine
The Java
Application
Programming
Interface (API)

Different Editions of Java
• Java Standard Edition (J2SE)
– J2SE can be used to develop client-side
standalone applications or applets.
• Java Enterprise Edition (J2EE)
– J2EE can be used to develop server-side
applications such as Java servlets, Java
ServerPages, and Java ServerFaces.
• Java Micro Edition (J2ME).
– J2ME can be used to develop applications for
mobile devices such as cell phones.

J2EE
• J2EE is a platform-independent, Java-centric
environment from Sun for developing,
building and deploying Web-based enterprise
applications online.

Why J2EE?
• Simplifies the complexity of a building n-tier
application
• Standardizes an API between components and
application server container
• J2EE Application Server and Containers
provide the framework services

J2EE Tiers
• Client Presentation
 HTML or Java applets
deployed in Browser
 XML documentations
transmitted through HTTP
 Java clients running in
Client Java Virtual Machine
(JVM)
• Presentation Logic
 Servlets or JavaServer
Pages running in web
server
• Application Logic
 Enterprise JavaBeans
running in Server

What are Servlets?
• The Servlet is a server-side programming
language class used for making dynamic web
pages. They reside within a servlet engine.
• Servlets receive and respond to requests from
Web clients, usually across HTTP, the
HyperText Transfer Protocol.
• They provide concurrency ,portability and
Efficiency.

Tasks of a Servlet
• Read the explicit data sent by the clients
(browsers).
• Read the implicit HTTP request data sent by
the clients (browsers).
• Process the data and generate results.
• Send the explicit data (i.e., the document) to
the clients (browsers).
• Send the implicit HTTP response to the clients
(browsers

Servlet life cycle
 All methods are performed by Container
 Initialize using init() method when requested.
 Service() method handles requests/clients.
The requests are forwarded to the appropriate
method (ie. doGet() or doPost())
 Server removes the servlet using destroy()
method

Basic Servlet example
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Test extends HttpServlet{
public void doGet(HttpServletRequest in,
HttpServletResponse out) throws ServletException,
IOException {
out.setContentType(“text/html”);
PrintWriter p = res.getWriter();
p.println(“<H1>HELLO, WORLD!</H1>”);
}
}

Working with Servlets
 All servlets must extend the HttpServlet or Servlet
class

public class MyServlet extends HttpServlet
 HttpServlet Class overrides service() method.
 Two most common HTTP request types. Under HTTP, there
are two methods available for sending parameters from the
browser to the web server.
 doPost(HttpServletRequest,HttpServletResponse);
Invoked whenever an HTTP POST request is issued through an
HTML form.Unlimited data can b send.
 doGet(HttpServletRequest,HttpServletResponse);
Invoked whenever an HTTP GET method from a URL request is
issued, or an HTML form. Limited data sending.

Transfer Of Control
HTML Servlet
abc.jsp
Abc(java file)
Abc.html
• sendRedirect(filename); sends control.
• RequestDispatcher(); sends Control+data
using :
Requestdispatcher rd= request.Getrequestdispatcher(“abc.Jsp”);
Rd.Forward(req,res): // to see o/p of only requesting servlet.
Rd.Include(req,res); //o/p of all previous servlets are shown.

Servlet Context & Servlet
Configuration
Servlet Context is some information which
has global scope. It works as static data.
ServletContext sc=getServletContext();
sc.setAttribute("user", “abc");
sc.getAttribute(“user”);
Servlet Configuration is the information
specific to a servlet.
ServletConfig sc = getServletConfig();

Session Handling
Session handling is used for tracking client’s session .
Types of session handling:-
URL re-writing
Hidden form field
Cookies
Http session

URL re-writing
You can append some extra data on the end of each URL that
identifies the session, and the server can associate that
session identifier with data it has stored about that session.
ex:-username and password will be appended to the URL.
Hidden Form Field
HTML forms have an entry that looks like the following:
<input type=“hidden” value=“username”>
This can be used to store information about the session.

Cookies
we can use HTTP cookies to store information about session
and each subsequent connection can look up the current
session and then extract information about that session from
some location on the server machine.
• Cookies are normal files
• Contains info of users
• Resides on the browser

Http Session
The info of users are stored in server -side. User have no
authority to modify the info.
Initialization of http session:
HttpSession hs= request.getSession();
By default session is TRUE . If false then previous session is
picked up.
How to add info in hs:-
hs.setAttribute(“name", "value”);

how to get info:-
HttpSession hs= request.getSession(false);
hs.getAttribute(“name”);
How to delete info:-
hs.invalidate();
HttpSession handling done as shown in following program:-

Database Handling
Java database connectivity (JDBC) is a standard application
programming interface (API) specification that is implemented
by different database vendors to allow Java programs to access
their database management systems. The JDBC API consists
of a set of interfaces and classes written in the Java
programming language.
Basic steps to use database in Java
• Establish a connection
• Create statements
• Execute SQL statements
• Get results

Loading drivers
Class.forName("oracle.jdbc.driver.OracleDriver");
– Dynamically loads a driver class, for Oracle database.
Making connections
Connection con=
DriverManager.getConnection(“Oracle:jdbc:oracle:thin:@l
ocalhost:1521:xc”,”username”,”password”);
– Establishes connection to database by obtaining
a Connection object .

Specifying SQL queries
Using prepared statements:-
Syntax- PreparedStatement ps= con.preparestatement(“SQL
QUERY”);
Execute Query
There are two operations to execute queries:-
• Select – ps.executeQuery();
• update – ps.executeUpdate();
To store data:-
ResultSet rs= ps.executeQuery();

To get the data from rs:-
• Row by row data is fetched.
Syntax:-
While( rs.next())
{
String s1= rs.getString(“name”);
Date d= rs.getDate(“date”);
}
The following program show the working:-

Java Server Pages
• Server-side programming technology that enables the creation of
dynamic. Released in 1999 by Sun Microsystems.
• Platform-independent method for building Web-based
applications.
• Uses static data usually HTML.
• To deploy and run JavaServer Pages, a compatible web server with
a servlet container, such as Apache Tomcat is required.
• Entire JSP page gets translated into a servlet (once), and servlet gets
invoked (for each request)
• JavaServer Pages (JSP) lets you separate the dynamic part of your
pages from the static HTML.
HTML tags and text
<% some JSP code here %>
HTML tags and text

Working of JSP…
Client
Server with JSP
Container
Java Engine
loads the JSP
page from
disk and
converts it
into a servlet
content.
.class
loads the
Servlet class
and executes
it. Server
produces an
o/p in HTTP
format during
exc.
Servlet Engine

Intro to Predefined variables-
(Implicit Objects)
created automatically when a web server processes a JSP page
• request: Object of HttpServletRequest (1st arg to doGet)
• response: : Object of HttpServletResponse (2nd arg to doGet)
• session
– The HttpSession associated with the request (unless disabled with the session
attribute of the page directive)
• out
– The stream (of type JspWriter) used to send output to the client
• application
– The ServletContext (for sharing data) as obtained via
getServletConfig().getContext().
• config - Object of ServletConfig
• pageContext - Object of PageContext in JSP for a single point of access
• page – variable synonym for this object

JSP Directives
Directives provide directions and instructions over
translation of JSP into servlet.
Page-defines attributes affecting structure of
servlet.
<%@ page contentType="text/html“
errorPage="error.jsp"import="java.util.*" %>
Include-contents of other files are included
statically in JSP
<%@ include file=”header.html” %>
Taglib-include external tag library in web page.
<%@ taglib uri="URIToTagLibrary" prefix="tagPrefix" %>

JSP Elements
• Expression:- It contains a scripting language expression that is evaluated,
converted to a String, and inserted where the expression appears in the
JSP file.
Syntax=> <%= expression %>
Eg: Current time: <%=new.java.util.Date() %>
• Declarations:- May contain one or more Java declarations to be inserted
into the class body of the generated servlet
Syntax=> <%! Java declarations %>
Eg:<%! Int i; %>
• Scriplets:-Consists of one or more Java statements to be inserted into the
generated servlet’s _jspService method (called by service).
Syntax=> <% java code %>
Eg: <%
String var1 = request.getParameter("name");
out.println(var1);
%>

JSP v/s Servlets
Servlets are strictly written in
Java .
Servlets must be given both
a servlet definition and one or
more mappings within the web
deployment descriptor
(web.xml).
Servlets are for generic
handling of an HTTP request.
Executed as a servlet itself
JSPs contain mixed dynamic
content.
JSPs do not require either,
allowing much quicker and less
brittle page creation.
JSPs are specifically targeted
and optimized to render a
response to the request in the
output language of choice
(typically HTML).
Code is compiled into a
servlet

Apache Struts Technology
A MVC Framework for Java Web
Applications

Agenda
• What is and Why Struts?
• How to install Struts in your WebApp ?
• Struts architecture
–Model
– Controller
– View

What is Struts ?
• Frameworks(Front-Ends) for Developing Java
web based applications
• free open-source
• Current Version: 1.1
• Based on architecture of MVC(Model-View-
Controller) Design Pattern

Why Struts?
• Flexible, extensible and structured front-ends
• Large user community
• Stable Framework
• Open source
• Easy to learn and use
• Feature-rich( like error handling and MVC )
• Works with existing web apps

Struts Installation
• Download the zip file from the Apache website
• Copy the zar files from the lib directory of the zip
file in WEB-INF/lib
• Editing web.xml file
Struts Servlet and Mapping code
• Create an empty struts-config.xml
Servlet Configuration code
• Start your server

Web Xml File
• web.xml includes:
– Configure ActionServlet instance and mapping
– Resource file as <init-param>
– servlet-config.xml file as <init-param>
– Define the Struts tag libraries
• web.xml is stored in WEB-INF/web.xml

Example: web.xml
<servlet>
<servlet-name>action</servlet-name>
<servlet-class>
org.apache.struts.action.ActionServlet
</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/struts-config.
xml</param value>
</init-param>
</servlet>

Struts Config File
(struts-config.xml)
• struts-config.xml contains three important
elements used to describe actions:
– <form-beans> contains FormBean
definitions including name and type (classname)
– <action-mapping> contains action
definitions Use an <action> element for each action
defined
– <global-forwards> contains your global
forward definitions

Struts Architecture
• Struts is an open-source framework for building more flexible, maintainable
and structured front-ends in Java web applications
•There are two key components in a web application:
–the data and business logic performed on this data
–the presentation of data
• Struts
–helps structuring these components in a Java web app.
–controls the flow of the web application, strictly separating these
components
–unifies the interaction between them
• This separation between presentation, business logic and control is
achieved by implementing the Model-View-Controller (MVC) Design
Pattern

Model-View-Controller(MVC)
• A famous design pattern
• Breaks an application into three parts
Model = Domain/Business Logic
The problem domain is represented by the Model.
View = Presentation/the pieces the user sees and
interacts with
The output to the user is represented by the View.
Controller = The part(s) that know how to use the model
to get something done
The input from the user is represented by Controller.

Model-View-Control
(Controller)
Servlet
BROWSER
Redirect
(View)
Request
Response JSP
MVC Design Pattern
(Model)
Java Bean
Servlet Container

Hibernate: An Introduction
• It is an object-relational mapping (ORM)
solution for Java
• We make our data persistent by storing it in a
database
• Hibernate takes care of this for us

Object-Relational Mapping
• It is a programming technique for converting
object-type data of an object oriented
programming language into database tables.
• Hibernate is used convert object data in JAVA
to relational database tables.

Why Hibernate and not JDBC?
• JDBC maps Java classes to database tables (and
from Java data types to SQL data types)
• Hibernate automatically generates the SQL
queries.
• Hibernate provides data query and retrieval
facilities and can significantly reduce
development time otherwise spent with manual
data handling in SQL and JDBC.
• Makes an application portable to all SQL
databases.

Hibernate vs. JDBC (an example)
• JDBC tuple insertion –
st.executeUpdate(“INSERT INTO book
VALUES(“Harry Potter”,”J.K.Rowling”));
• Hibernate tuple insertion –
session.save(book1);

Architecture
Hibernate sits between your
code and the database
Maps persistent objects to
tables in the database

Tiles
• Tiles are like individual visual component,
• And using Tiles Framework, you can develop a
web page by including different tiles or
component.
• Tile layout is a JSP page which defines the
layout or defines the look and feel and where
each tile (for example header, body, footer )
are placed.

Instead of writing
header , and footer
on each and every
JSP page, how good
will it be having
common tile for
those components
and include in all the
pages.

Advance Java Topics (J2EE)

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