Software environment

Software Environment
Java Technology
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
 Architecture neutral
 Object oriented
 Portable
 Distributed
 High performance
 Interpreted
 Multithreaded
 Robust
 Dynamic
 Secure
With most programming languages, you either compile or interpret a
program so that you can run it on your computer. The Java programming language

is unusual in that a program is both compiled and interpreted. With the compiler,
first you translate a program into an intermediate language called Java byte codes
—the platform-independent codes interpreted by the interpreter on the Java
platform. The interpreter parses and runs each Java byte code instruction on the
computer. Compilation happens just once; interpretation occurs each time the
program is executed. The following figure illustrates how this works.
You can think of Java byte codes as the machine code instructions for the
Java Virtual Machine (Java VM). Every Java interpreter, whether it’s a
development tool or a Web browser that can run applets, is an implementation of
the Java VM. Java byte codes help make “write once, run anywhere” possible. You
can compile your program into byte codes on any platform that has a Java
compiler. The byte codes can then be run on any implementation of the Java VM.
That means that as long as a computer has a Java VM, the same program written in
the Java programming language can run on Windows 2000, a Solaris workstation,
or on an iMac.

The Java Platform
A platform is the hardware or software environment in which a
program runs. We’ve already mentioned some of the most popular platforms
like Windows 2000, Linux, Solaris, and MacOS. Most platforms can be
described as a combination of the operating system and 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 VirtualMachine (Java VM)
 The Java Application Programming Interface (Java API)
You’ve already been introduced to the Java VM. It’s the base for the Java
platform and is ported onto various hardware-based platforms.
The Java API is a large collection of ready-made software components
that provide many useful capabilities, such as graphical user interface (GUI)
widgets. The Java API is grouped into libraries of related classes and
interfaces; these libraries are known as packages. The next section, What

Can Java Technology Do? Highlights what functionality some of the
packages in the Java API provide.
The following figure depicts a program that’s running on the Java
platform. As the figure shows, the Java API and the virtual machine insulate
the program from the hardware.
Native code is code that after you compile it, the compiled code runs
on a specific hardware platform. As a platform-independent environment,
the Java platform can be a bit slower than native code. However, smart
compilers, well-tuned interpreters, and just-in-time byte code compilers can
bring performance close to that of native code without threatening
portability.
What Can Java TechnologyDo?
The most common types of programs written in the Java programming
language are applets and applications. If you’ve surfed the Web, you’re
probably already familiar with applets. An applet is a program that adheres
to certain conventions that allow it to run within a Java-enabled browser.
However, the Java programming language is not just for writing cute,
entertaining applets for the Web. The general-purpose, high-level Java
programming language is also a powerful software platform. Using the
generous API, you can write many types of programs.
An application is a standalone program that runs directly on the Java
platform. A special kind of application known as a server serves and

supports clients on a network. Examples of servers are Web servers, proxy
servers, mail servers, and print servers. Another specialized program is a
servlet. A servlet can almost be thought of as an applet that runs on the
server side. Java Servlets are a popular choice for building interactive web
applications, replacing the use of CGI scripts. Servlets are similar to applets
in that they are runtime extensions of applications. Instead of working in
browsers, though, servlets run within Java Web servers, configuring or
tailoring the server.
How does the API support all these kinds of programs? It does so with
packages of software components that provides a wide range of
functionality. Every full implementation of the Java platform gives you the
following features:
 The essentials: Objects, strings, threads, numbers, input and output,
data structures, system properties, date and time, and so on.
 Applets: The set of conventions used by applets.
 Networking: URLs, TCP (Transmission Control Protocol), UDP
(User Data gram Protocol) sockets, and IP (Internet Protocol)
addresses.
 Internationalization: Help for writing programs that can be localized
for users worldwide. Programs can automatically adapt to specific
locales and be displayed in the appropriate language.
 Security: Both low level and high level, including electronic
signatures, public and private key management, access control, and
certificates.
 Software components: Known as JavaBeansTM, can plug into
existing componentarchitectures.

 Object serialization: Allows lightweight persistence and
communication via Remote Method Invocation (RMI).
 Java Database Connectivity (JDBCTM
): Provides uniform access to
a wide range of relational databases.
The Java platform also has APIs for 2D and 3D graphics, accessibility,
servers, collaboration, telephony, speech, animation, and more. The
following figure depicts what is included in the Java 2 SDK.
How Will JavaTechnologyChangeMy Life?
We can’t promise you fame, fortune, or even a job if you learn the Java
programming language. Still, it is likely to make your programs better and
requires less effort than other languages. We believe that Java technology
will help you do the following:
 Get started quickly: Although the Java programming language is a
powerful object-oriented language, it’s easy to learn, especially for
programmers already familiar with C or C++.

 Write less code: Comparisons of program metrics (class counts,
method counts, and so on) suggest that a program written in the Java
programming language can be four times smaller than the same
program in C++.
 Write better code: The Java programming language encourages good
coding practices, and its garbage collection helps you avoid memory
leaks. Its object orientation, its JavaBeans component architecture,
and its wide-ranging, easily extendible API let you reuse other
people’s tested codeand introduce fewer bugs.
 Develop programs more quickly: Your development time may be as
much as twice as fast versus writing the same program in C++. Why?
You write fewer lines of code and it is a simpler programming
language than C++.
 Avoid platform dependencies with 100% Pure Java: You can keep
your program portable by avoiding the use of libraries written in other
languages. The 100% Pure JavaTM Product Certification Program has a
repository of historical process manuals, white papers, brochures, and
similar materials online.
 Write once, run anywhere: Because 100% Pure Java programs are
compiled into machine-independent byte codes, they run consistently
on any Java platform.
 Distribute software more easily: You can upgrade applets easily
from a central server. Applets take advantage of the feature of
allowing new classes to be loaded “on the fly,” without recompiling
the entire program.

ODBC
Microsoft Open Database Connectivity (ODBC) is a standard programming
interface for application developers and database systems providers. Before ODBC
became a de facto standard for Windows programs to interface with database
systems, programmers had to use proprietary languages for each database they
wanted to connect to. Now, ODBC has made the choice of the database system
almost irrelevant from a coding perspective, which is as it should be. Application
developers have much more important things to worry about than the syntax that is
needed to port their program from one database to another when business needs
suddenly change.
Through the ODBC Administrator in Control Panel, you can specify the
particular database that is associated with a data source that an ODBC application
program is written to use. Think of an ODBC data source as a door with a name on
it. Each door will lead you to a particular database. For example, the data source
named Sales Figures might be a SQL Server database, whereas the Accounts
Payable data source could refer to an Access database. The physical database
referred to by a data sourcecan reside anywhere on the LAN.
The ODBC system files are not installed on your system by Windows 95.
Rather, they are installed when you setup a separate database application, such as
SQL Server Client or Visual Basic 4.0. When the ODBC icon is installed in
Control Panel, it uses a file called ODBCINST.DLL. It is also possible to
administer your ODBC data sources through a stand-alone program called
ODBCADM.EXE. There is a 16-bit and a 32-bit version of this program and each
maintains a separate list of ODBC data sources.

From a programming perspective, the beauty of ODBC is that the
application can be written to use the same set of function calls to interface with any
data source, regardless of the database vendor. The source code of the application
doesn’t change whether it talks to Oracle or SQL Server. We only mention these
two as an example. There are ODBC drivers available for several dozen popular
database systems. Even Excel spreadsheets and plain text files can be turned into
data sources. The operating system uses the Registry information written by
ODBC Administrator to determine which low-level ODBC drivers are needed to
talk to the data source (such as the interface to Oracle or SQL Server). The loading
of the ODBC drivers is transparent to the ODBC application program. In a
client/server environment, the ODBC API even handles many of the network
issues for the application programmer.
The advantages of this scheme are so numerous that you are probably
thinking there must be some catch. The only disadvantage of ODBC is that it isn’t
as efficient as talking directly to the native database interface. ODBC has had
many detractors make the charge that it is too slow. Microsoft has always claimed
that the critical factor in performance is the quality of the driver software that is
used. In our humble opinion, this is true. The availability of good ODBC drivers
has improved a great deal recently. And anyway, the criticism about performance
is somewhat analogous to those who said that compilers would never match the
speed of pure assembly language. Maybe not, but the compiler (or ODBC) gives
you the opportunity to write cleaner programs, which means you finish sooner.
Meanwhile, computers get faster every year.
JDBC
In an effort to set an independent database standard API for Java; Sun
Microsystems developed Java Database Connectivity, or JDBC. JDBC offers a

generic SQL database access mechanism that provides a consistent interface to a
variety of RDBMSs. This consistent interface is achieved through the use of “plug-
in” database connectivity modules, or drivers. If a database vendor wishes to have
JDBC support, he or she must provide the driver for each platform that the
database and Java run on.
To gain a wider acceptance of JDBC, Sun based JDBC’s framework on
ODBC. As you discovered earlier in this chapter, ODBC has widespread support
on a variety of platforms. Basing JDBC on ODBC will allow vendors to bring
JDBC drivers to market much faster than developing a completely new
connectivity solution.
JDBC was announced in March of 1996. It was released for a 90 day public
review that ended June 8, 1996. Because of user input, the final JDBC v1.0
specification was released soonafter.
The remainder of this section will cover enough information about JDBC for you
to know what it is about and how to use it effectively. This is by no means a
complete overview of JDBC. That would fill an entire book.
JDBC Goals
Few software packages are designed without goals in mind. JDBC is one
that, because of its many goals, drove the development of the API. These goals, in
conjunction with early reviewer feedback, have finalized the JDBC class library
into a solid framework for building database applications in Java.
The goals that were set for JDBC are important. They will give you some
insight as to why certain classes and functionalities behave the way they do. The
eight design goals for JDBC are as follows:
1. SQL Level API

The designers felt that their main goal was to define a SQL interface for
Java. Although not the lowest database interface level possible, it is at a low
enough level for higher-level tools and APIs to be created. Conversely, it is at a
high enough level for application programmers to use it confidently. Attaining
this goal allows for future tool vendors to “generate” JDBC code and to hide
many of JDBC’s complexities from the end user.
2. SQL Conformance
SQL syntax varies as you move from database vendor to database vendor. In
an effort to support a wide variety of vendors, JDBC will allow any query
statement to be passed through it to the underlying database driver. This allows
the connectivity module to handle non-standard functionality in a manner that is
suitable for its users.
3. JDBC must be implemental on top of common database interfaces
The JDBC SQL API must “sit” on top of other common SQL level APIs.
This goal allows JDBC to use existing ODBC level drivers by the use of a
software interface. This interface would translate JDBC calls to ODBC and
vice versa.
4. Providea Java interfacethat is consistent withthe rest of the Java system
Because of Java’s acceptance in the user community thus far, the designers
feel that they should not stray from the current design of the core Java system.
5. Keep it simple
This goal probably appears in all software design goal listings. JDBC is no
exception. Sun felt that the design of JDBC should be very simple, allowing for
only one method of completing a task per mechanism. Allowing duplicate
functionality only serves to confusethe users of the API.

6. Use strong, static typing wherever possible
Strong typing allows for more error checking to be done at compile time;
also, less error appear at runtime.
7. Keep the common cases simple
Because more often than not, the usual SQL calls used by the programmer
are simple SELECT’s, INSERT’s, DELETE’s and UPDATE’s, these queries
should be simple to perform with JDBC. However, more complex SQL
statements should also be possible.
Finally we decided to proceed the implementation using Java Networking.
And for dynamically updating the cache table we go for MS Access
database.
Java ha two things: a programming language and a platform.
Java is a high-level programming language that is all of the
following
Simple Architecture-neutral
Object-oriented Portable
Distributed High-performance
Interpreted multithreaded
Robust Dynamic
Secure

Java is also unusual in that each Java program is both compiled and
interpreted. With a compile you translate a Java program into an
intermediate language called Java byte codes the platform-independent
codeinstruction is passed and run on the computer.
Compilation happens just once; interpretation occurs each time the
program is executed. The figure illustrates how this works.
You can think of Java byte codes as the machine code instructions for
the Java Virtual Machine (Java VM). Every Java interpreter, whether it’s
a Java development tool or a Web browser that can run Java applets, is an
implementation of the Java VM. The Java VM can also be implemented
in hardware.
Java Program
Compilers
Interpreter
My Program

Java byte codes help make “write once, run anywhere” possible. You
can compile your Java program into byte codes on my platform that has a
Java compiler. The byte codes can then be run any implementation of the
Java VM. For example, the same Java program can run Windows NT,
Solaris, and Macintosh.
Networking
TCP/IP stack
The TCP/IP stackis shorter than the OSI one:

TCP is a connection-oriented protocol;UDP (User Datagram Protocol)
is a connectionless protocol.
IP datagram’s
The IP layer provides a connectionless and unreliable delivery system.
It considers each datagram independently of the others. Any association
between datagram must be supplied by the higher layers. The IP layer
supplies a checksum that includes its own header. The header includes the
sourceand destination addresses. TheIP layer handles routing through an
Internet. It is also responsible for breaking up large datagram into smaller
ones for transmission and reassembling them at the other end.

UDP
UDP is also connectionless and unreliable. What it adds to IP is a
checksum for the contents of the datagram and portnumbers. These are
used to give a client/server model - see later.
TCP
TCP supplies logic to give a reliable connection-oriented protocol
above IP. It provides a virtual circuit that two processes canuse to
communicate.
Internet addresses
In order to use a service, you must be able to find it. The Internet uses
an address scheme for machines so that they can be located. The address is
a 32 bit integer which gives the IP address. This encodes a network ID and
more addressing. The network ID falls into various classes according to the
size of the network address.
Network address
Class A uses 8 bits for the network address with 24 bits left over for
other addressing. Class B uses 16 bit network addressing. Class C uses 24
bit network addressing and class D uses all 32.

Subnet address
Internally, the UNIX network is divided into sub networks. Building 11
is currently on one sub network and uses 10-bit addressing, allowing 1024
different hosts.
Host address
8 bits are finally used for host addresses within our subnet. This places
a limit of 256 machines that can be on the subnet.
Totaladdress
The 32 bit address is usually written as 4 integers separated by dots.
Port addresses
A service exists on a host, and is identified by its port. This is a 16 bit
number. To send a message to a server, you send it to the port for that
service of the host that it is running on. This is not location transparency!
Certain of these ports are "well known".

Sockets
A socket is a data structure maintained by the system to handle network
connections. A socketis created using the call socket. It returns an integer
that is like a file descriptor. In fact, under Windows, this handle can be
used with Read File and Write File functions.
#include <sys/types.h>
#include <sys/socket.h>
int socket(int family, int type, int protocol);
Here "family" will be AF_INET for IP communications, protocolwill
be zero, and type will depend on whether TCP or UDP is used. Two
processes wishing to communicate over a network create a socket each.
These are similar to two ends of a pipe - but the actual pipe does not yet
exist.
JFree Chart
JFreeChart is a free 100% Java chart library that makes it easy for
developers to display professional quality charts in their applications.
JFreeChart's extensive feature set includes:
A consistent and well-documented API, supporting a wide range of
chart types;
A flexible design that is easy to extend, and targets both server-side
and client-side applications;

Support for many output types, including Swing components, image
files (including PNG and JPEG), and vector graphics file formats (including
PDF, EPS and SVG);
JFreeChart is "open source" or, more specifically, free software. It is
distributed under the terms of the GNU Lesser General Public Licence
(LGPL), which permits use in proprietary applications.
1. Map Visualizations
Charts showing values that relate to geographical areas. Some
examples include: (a) population density in each state of the United States,
(b) income per capita for each country in Europe, (c) life expectancy in each
country of the world. The tasks in this project include:
Sourcing freely redistributable vector outlines for the countries of the
world, states/provinces in particular countries (USA in particular, but also
other areas);
Creating an appropriate dataset interface (plus default
implementation), a rendered, and integrating this with the existing XYPlot
class in JFreeChart;
Testing, documenting, testing some more, documenting some more.
2. TimeSeriesChart Interactivity
Implement a new (to JFreeChart) feature for interactive time series charts --- to
display a separate control that shows a small version of ALL the time series
data, with a sliding "view" rectangle that allows you to select the subset of the
time series data to display in the main chart.

3. Dashboards
There is currently a lot of interest in dashboard displays. Create a flexible
dashboard mechanism that supports a subset of JFreeChart chart types (dials,
pies, thermometers, bars, and lines/time series) that can be delivered easily via
both Java Web Start and an applet.
4. Property Editors
The property editor mechanism in JFreeChart only handles a small subset of
the properties that can be set for charts. Extend (or reimplement) this
mechanism to provide greater end-user control over the appearance of the
charts.
J2ME (Java 2 Micro edition):-
Sun Microsystems defines J2ME as "a highly optimized Java run-time
environment targeting a wide range of consumer products, including pagers,
cellular phones, screen-phones, digital set-top boxes and car navigation systems."
Announced in June 1999 at the JavaOne Developer Conference, J2ME brings the

cross-platform functionality of the Java language to smaller devices, allowing
mobile wireless devices to share applications. With J2ME, Sun has adapted the
Java platform for consumer products that incorporate or are based on small
computing devices.
1. GeneralJ2ME architecture

J2ME uses configurations and profiles to customize the Java Runtime Environment
(JRE). As a complete JRE, J2ME is comprised of a configuration, which
determines the JVM used, and a profile, which defines the application by adding
domain-specific classes. The configuration defines the basic run-time environment
as a set of core classes and a specific JVM that run on specific types of devices.
We'll discuss configurations in detail in the The profile defines the application;
specifically, it adds domain-specific classes to the J2ME configuration to define
certain uses for devices. We'll cover profiles in depth in the The following graphic
depicts the relationship between the different virtual machines, configurations, and
profiles. It also draws a parallel with the J2SE API and its Java virtual machine.
While the J2SE virtual machine is generally referred to as a JVM, the J2ME virtual
machines, KVM and CVM, are subsets of JVM. Both KVM and CVM can be

thought of as a kind of Java virtual machine -- it's just that they are shrunken
versions of the J2SE JVM and are specific to J2ME.
2.Developing J2ME applications
Introduction In this section, we will go over some considerations you need to keep
in mind when developing applications for smaller devices. We'll take a look at the
way the compiler is invoked when using J2SE to compile J2ME applications.
Finally, we'll explore packaging and deployment and the role preverification plays
in this process.
3.Designconsiderations forsmall devices
Developing applications for small devices requires you to keep certain strategies in
mind during the design phase. It is best to strategically design an application for a
small device before you begin coding. Correcting the code because you failed to
consider all of the "gotchas" before developing the application can be a painful
process. Here are some design strategies to consider:
* Keep it simple. Remove unnecessary features, possibly making those features a
separate, secondaryapplication.

* Smaller is better. This consideration should be a "no brainer" for all developers.
Smaller applications use less memory on the device and require shorter installation
times. Consider packaging your Java applications as compressed Java Archive (jar)
files.
* Minimize run-time memory use. To minimize the amount of memory used at run
time, use scalar types in place of object types. Also, do not depend on the garbage
collector. You should manage the memory efficiently yourself by setting object
references to null when you are finished with them. Another way to reduce run-
time memory is to use lazy instantiation, only allocating objects on an as-needed
basis. Other ways of reducing overall and peak memory use on small devices are to
release resources quickly, reuse objects, and avoid exceptions.
4.Configurations overview
The configuration defines the basic run-time environment as a set of core classes
and a specific JVM that run on specific types of devices. Currently, two
configurations exist for J2ME, though others may be defined in the future:
* Connected Limited Device Configuration (CLDC) is used specifically with
the KVM for 16-bit or 32-bit devices with limited amounts of memory. This is the
configuration (and the virtual machine) used for developing small J2ME

applications. Its size limitations make CLDC more interesting and challenging
(from a development point of view) than CDC. CLDC is also the configuration that
we will use for developing our drawing tool application. An example of a small
wireless device running small applications is a Palm hand-held computer.
* Connected Device Configuration (CDC) is used with the C virtual machine
(CVM) and is used for 32-bit architectures requiring more than 2 MB of memory.
An example of such a device is a Net TV box.
5.J2ME profiles
What is a J2ME profile?
As we mentioned earlier in this tutorial, a profile defines the type of device
supported. The Mobile Information Device Profile (MIDP), for example, defines
classes for cellular phones. It adds domain-specific classes to the J2ME
configuration to define uses for similar devices. Two profiles have been defined for
J2ME and are built upon CLDC: KJava and MIDP. Both KJava and MIDP are
associated with CLDC and smaller devices. Profiles are built on top of
configurations. Because profiles are specific to the size of the device (amount of
memory) on which an application runs, certain profiles are associated with certain
configurations.

A skeleton profile upon which you can create your own profile, the Foundation
Profile, is available for CDC.
Profile 1: KJava
KJava is Sun's proprietary profile and contains the KJava API. The KJava profile is
built on top of the CLDC configuration. The KJava virtual machine, KVM, accepts
the same byte codes and class file format as the classic J2SE virtual machine.
KJava contains a Sun-specific API that runs on the Palm OS. The KJava API has a
great deal in common with the J2SE Abstract Windowing Toolkit (AWT).
However, because it is not a standard J2ME package, its main package is
com.sun.kjava. We'll learn more about the KJava API later in this tutorial when we
develop some sample applications.
Profile 2: MIDP
MIDP is geared toward mobile devices such as cellular phones and pagers. The
MIDP, like KJava, is built upon CLDC and provides a standard run-time
environment that allows new applications and services to be deployed dynamically
on end user devices. MIDP is a common, industry-standard profile for mobile
devices that is not dependent on a specific vendor. It is a complete and supported
foundation for mobile application
development. MIDP contains the following packages, the first three of which are
core CLDC packages, plus three MIDP-specific packages.
* java.lang
* java.io
* java.util

* javax.microedition.io
* javax.microedition.lcdui
* javax.microedition.midlet
* javax.microedition.rms

Software environment

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