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AGENDA

• CLIENT-SERVER ARCHITECTURE

• HTTP PROTOCOL

• THICK CLIENT

• THIN CLIENT

• WEB SERVER

• APPLICATION SERVER

• PACKAGING APPLICATIONS FOR DEPLOYMENT (JAR, WAR, EAR)

• DEPLOYMENT DESCRIPTOR (WEB.XML)

• URL

CLIENT-SERVER ARCHITECTURE

Fig.1.1 Client-Server Architecture

EXAMPLE OF CLIENT-SERVER ARCHITECTURE

Fig.1.2 Example of Client-Server Architecture

HTTP METHODS

• OPTIONS

•GET• HEAD

• POST• PUT

• DELETE

• TRACE

• CONNECT

HTTP STATUS CODES• 1XX –INFORMATIONAL

• 2XX –SUCCESS

• 3XX –REDIRECTION

• 4XX –CLIENT ERROR

• 5XX –SERVER ERROR

THICK CLIENT(FAT CLIENT)

• A THICK CLIENT IS A COMPUTER THAT DOES NOT REQUIRE A CONNECTION TO A SERVER SYSTEM IN ORDER TO RUN (UNLIKE A THIN CLIENT), ALTHOUGH THEY CAN BENEFIT FROM BEING CONNECTED TO A NETWORK AND A SERVER. 

FIG.1.3. PERSONAL COMPUTER, A FORM OF THICK CLIENT.

• THICK CLIENTS HAVE THEIR OWN OPERATING SYSTEM AND SOFTWARE APPLICATIONS AND CAN BE USED OFFLINE.

THIN CLIENT

• THIN CLIENTS ARE NOT TYPICAL COMPUTERS, BUT RATHER A TERMINAL THAT RELIES ON ANOTHER COMPUTER SYSTEM (USUALLY A SERVER) TO SUPPLY THE OPERATING SYSTEM AND SOFTWARE APPLICATIONS NEEDED BY THE USER. 

FIG.1.4. THIN CLIENTS CONNECTED TO THEIR SERVER VIA A COMPUTER NETWORK.

WEB SERVER

• A WEB SERVER IS A COMPUTER SYSTEM THAT PROCESSES REQUESTS VIA HTTP, THE BASIC NETWORK PROTOCOL USED TO DISTRIBUTE INFORMATION ON THE WORLD WIDE WEB.

• THE TERM CAN REFER EITHER TO THE ENTIRE SYSTEM, OR SPECIFICALLY TO THE SOFTWARE THAT ACCEPTS AND SUPERVISES THE HTTP REQUESTS.

• APACHE AND IIS ARE THE MOST USED WEB SERVERS ON THE INTERNET.

APPLICATION SERVER• AN APPLICATION SERVER CAN BE EITHER A SOFTWARE FRAMEWORK THAT

PROVIDES A GENERALIZED APPROACH TO CREATING AN APPLICATION-SERVER IMPLEMENTATION, REGARD TO WHAT THE APPLICATION FUNCTIONS ARE, OR THE SERVER PORTION OF A SPECIFIC IMPLEMENTATION INSTANCE.

• IN EITHER CASE, THE SERVER'S FUNCTION IS DEDICATED TO THE EFFICIENT EXECUTION OF PROCEDURES (PROGRAMS, ROUTINES, SCRIPTS) FOR SUPPORTING ITS APPLIED APPLICATIONS.

PACKAGING JAVA APPLICATIONS

• JAR –JAVA ARCHIVE

• JAR (JAVA ARCHIVE) IS A PACKAGE FILE FORMAT TYPICALLY USED TO AGGREGATE MANY JAVA CLASS FILES AND ASSOCIATED METADATA AND RESOURCES (TEXT, IMAGES, ETC.) INTO ONE FILE TO DISTRIBUTE APPLICATION SOFTWARE OR LIBRARIES ON THE JAVA PLATFORM.

PACKAGING JAVA WEB APPLICATIONS

• WAR –WEB APPLICATION ARCHIVE

PACKAGING JAVA ENTERPRISE APPLICATIONS

• EAR –ENTERPRISE APPLICATION ARCHIVE

DEPLOYMENT DESCRIPTOR

• A DEPLOYMENT DESCRIPTOR IS AN XML DOCUMENT WITH AN .XML EXTENSION THAT DESCRIBES THE DEPLOYMENT SETTINGS OF AN APPLICATION, A MODULE, OR A COMPONENT. BECAUSE DEPLOYMENT DESCRIPTOR INFORMATION IS DECLARATIVE, IT CAN BE CHANGED WITHOUT THE NEED TO MODIFY THE SOURCE CODE.

• AT RUNTIME, THE JAVA EE SERVER READS THE DEPLOYMENT DESCRIPTOR AND ACTS UPON THE APPLICATION, MODULE, OR COMPONENT ACCORDINGLY.

( E.G. : WEB.XML, APPLICATION.XML )

WEB.XML• A WEB APPLICATION'S DEPLOYMENT DESCRIPTOR DESCRIBES THE CLASSES,

RESOURCES AND CONFIGURATION OF THE APPLICATION AND HOW THE WEB SERVER USES THEM TO SERVE WEB REQUESTS.

• WHEN THE WEB SERVER RECEIVES A REQUEST FOR THE APPLICATION, IT USES THE DEPLOYMENT DESCRIPTOR TO MAP THE URL OF THE REQUEST TO THE CODE THAT OUGHT TO HANDLE THE REQUEST.

•  WEB.XML IS PART OF THE SERVLET STANDARD FOR WEB APPLICATIONS.

1.     CONFIGURING AND MAPPING A SERVLET

2.     SERVLET INIT PARAMETERS

3.     SERVLET LOAD-ON-STARTUP

4.     CONTEXT PARAMETERS

URL• URL IS AN ACRONYM FOR UNIFORM RESOURCE LOCATOR AND IS A REFERENCE

(AN ADDRESS) TO A RESOURCE ON THE INTERNET.

URL=PROTOCOL IDENTIFIER + RESOURCE NAME

[SCHEME://HOSTNAME:PORT/PATH?NAME=VALUE]

MAKE THINGS AS SIMPLE AS YOU CAN BUT NOT SIMPLER EINSTEIN

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