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Library Management System Essay

Name of the Project Vision

Online Library Online Library is a system, which maintains books in the server in any format. It allows storing books, documents, audio and video files. User can Search and open documents by giving a simple query. Online Library Management System is a system, which maintains books, documents, audio/video files. To use this system user must be a member in this. Then user allowed storing books, documents, A/V files. Then user can search by giving a simple query. It is very difficult search books manually. Online Library makes easy.

Deliverables / Functional Specifications

Online Library uses user internal feedback from user to improve search process in every searching. It also uses indexing to locate documents very fast in searching which relate to query. Main aim of online Library system is providing highly relevant documents in very short period after giving query. It is just like Search Engine. It uses Vector space Model and Probabilistic Model to find similarity coefficient, weights. User Interface Requirements Database Centralized ONLINE LIBRARY BY M.SATHISH KUMAR Page 2

Browser based

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Requirements Integration Requirements Preferred Technologies J2EE Technologies i.e. JSP, Servlets, jdbc Frontend: – Html, JavaScript, Java Server pages. Backend: – Oracle 10g. Hardware Requirement Pentium 4 processor with 256 MB RAM, 40 GB Hard disk Web based Interface

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INTRODUCTION

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INTRODUTION
Online Library Management System is a system, which maintains books, documents, audio/video files. To use this system user must be a member in this. Then user allowed storing books, documents, A/V files. Then user can search by giving a simple query. It is very difficult search books manually. Online Library makes easy. Online Library uses user internal feedback from user to improve search process in every searching. It also uses indexing to locate documents very fast in searching which relate to query. Main aim of online Library system is providing highly relevant documents in very short period after giving query. It is just like Search Engine. It uses Vector space Model and Probabilistic Model to find similarity coefficient, weights.

Existing System
Early days Libraries are managed manually. It required lot of time to record or to retrieve the details. The employees who have to record the details must perform their job very carefully. Even a small mistake would create many problems. Security of information is very less. Report generations of all the information is very tough task. Maintenance of Library catalogue and arrangement of the books to the catalogue is very complex task. In addition to its maintenance of member details, issue dates and return dates etc. manually is a complex task. All the operations must be performed in perfect manner for the maintenance of the library without any degradation, which may finally result in the failure of the entire system.

Benefits of automation
Automation is procedure of converting a traditional system in to a computer organization. To overcome the defects of the existing system automation was introduced by the computerization of organization we get many benefits.

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The main objectives of undertaking this project are:         The students will register them through Online Individually each member will have his account through which he can access the information he needs. Books, documents, A/V files are stored in server. User will enter simple query in text box and click on the Search button. Server takes the request and processes it. Returns hyper links of documents with their names, ranks weights and description. If the user clicks on name of the document then it will open with respective program and rank of document will increase for that query.(for example .pdf files with Adobe Reader) User can upload documents, books and a/v files. Time consuming is low, gives accurate results, reliability can be improved with the help of security.

Proposed System:
To solve the inconveniences as mentioned above, an Online Library proposed.

PROCESS LOGIC:
1. The user inputs data (e.g.: fills out an HTML form and clicks the submit button.) 2. The client (Browser) sends the data to the web server in a standard format (i.e., the GET method or the POST method). 3. The web server launches the program specified by the user and feeds it the input (form) data. 4. The program (e.g.: servlet) processes the form data and produces another HTML page. 5. The web server sends back the HTML page to the browser. The web browser then displays the response page.

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ANALYSIS
Analysis is the process of understanding the existing system by gathering and interpreting the facts, diagnosing the problems. It is not just to determining the how best to solve the manual system problems, it should also work for the system observes the feasibility of system then design, coding phases will be executed. Analysis phase delivers requirements specification .The system specification serves as an interface between the designer and developer as well as between developers and users. This describes the external behavior of the software without bothering about the internal implementation. Specification must be carefully checked for suitability, omission, inconsistencies and ambiguities. Problem analysis is performed to getting a clear understanding of the needs of the clients and the users and what exactly desired form the software.

Analysis leads to the actual specification. During the process of analysis, a massive amount of information is collected in the form of interviews, questionnaires, and information from documentation, and so forth. The major problem during analysis is resolving how to organize the information from documentation, and so forth. So the information can be effectively evaluated for completeness and consistency.

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REQUIREMENT SPECIFICATION
FUNCTIONAL MODEL / USE CASE MODEL IDENTIFYING ACTOR:
1. Administrator: He should register new Users, Delete Users etc. He can upload new documents, Documents, and A/V files. 2. User: He should register in site in order to access books. He can search for books. He can upload new books, documents, and A/V files into server.

IDENTIFYING SCENARIOS:
A Scenario is a scene, which explains a particular situation in more visualized model. A scenario consists of actors, scenes, and flow of events. In our project, we have the following scenarios:

Scenario for Searching of EBooks, Document or A/V file:

Scene Name Actors Flow of events

Searching for books. User/Administrator User Opens home page of site. It will display text box and Search button. User simply enter query into text box, clicks on Search button. Browser sends request to the server. Server search documents for query and sends hyperlinks to documents (with weight, ranks, and a small description about document) in order of relevance to the query.

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Scenario a for Opening EBook, Document or A/V file:

Scene Name Actors Flow of events

Opening Book, Document, or A/V file. User / Administrator User clicks on hyperlink of Document by reading description about document that had displayed below hyperlink. Then browser sends a request to the server again. The request contains name of document which user wants to open. The server will increase rank for document with respect to query into order to increase the relevance. Then server sends the document file in the form of response to browser. Now browser will open the document by using related application program on client system. (For example if server sent .mp3 file then browser opens it by using audio player, which installed on client‟s computer. Of course, Browser needs permeation of System Administrator to access application program.)

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Scenario for Uploading a EBook, Document or A/V file into Server:

Scene Name Actors Flow of events

Uploading Administrator / User First User clicks on hyperlink of “Upload document”. Then browser sends request to upload file. Server return a webpage to browser it contains text box and browse button. By clicking on browse button a file window is displayed which allows to user to select a document from clients computer. After selecting document users click on upload button. Server checks for its extension. If document is.exe file server will not allow uploading file for the purpose of security. Then server insert name of document into documents table with unique document id. Then server creates index for document and insert into indexes table. Server returns a webpage, which contains confirmation and document id.

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Scenario for Modifying Users:

Scene Name Actors Flow of events

Modifying Users Administrator If login user is admin then homepage contains a special Hyperlink that “modify user.” If admin clicks on that hyperlink he will navigate to another webpage which contains details of users. In that
admin can modify user details admin can delete users who violated terms of site.

IDENTIFYING USE CASES:
A use case is a description of systems behaviour from a user‟s standpoint. It is a tried and true technique for gathering systems requirement from a user‟s point of view.

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USE CASE DIAGRAMS
Use case diagram for entire Online Library System:

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Use Case Diagram for Searching:

Use case Diagram for Uploading file:

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SEQUENCE DIAGRAMS
Sequence Diagram for Searching:

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Sequence Diagram for uploading file:

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Sequence Diagram for Opening file:

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COLLABORATION DIAGRAMS
Collaboration Diagram for Searching:

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Collaboration Diagram for uploading file:

Collaboration Diagram for Opening file:

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ACTIVITY DIAGRAMS
Activity Diagram for Searching:

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Activity Diagram for Uploading file:

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Activity Diagram for Opening file:

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CLASS DIAGRAMS
DBHandler Class: DBHandler is respnosible for performing all operations which are need interaction with Database. It perform all operation in database like inserting document, creating index, inserting query, mating database consistency , creating tables, recovering database when database crashed. It highly simplifies maintains of database. Adminstrator need not worry about database at any time.

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VectroSpaceModel Class: VectorSpaceModel is class it responsible for calculating similarity coefficients of documents with respect to query. After calculating similarity coefficient it passes documents with similarity coefficients to probabilistic model class, which will finds weights using similarity coefficients.

ProbabilisticModel Class: Probabilisticmodel class responsible for calculating weights for documents using similarity coefficients. After calculating weights, it will get ranks for documents from rank table. And return documents to Search class.

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Read Class: Read class for responsible for reading text from text files. It will read text from different format of text files. For example .doc, .pdf, .xls, .txt, .html etc. It read reads text and clean text and returns as string. If the file is not text file then it will return name and extension of file as string.

Search Class: Search Class acts as driver class. It does not perform any tasks. It makes all class working together.

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DEPLOYMENT DIAGRAM

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DESIGN
SOFTWARE STRUCTURE: Software is fundamental characteristic of computer software.

Software structure is to decompose the complex groups of module into sub modules i.e., Process, Menus, Inputs and Reports. The most general form of the software structure is the network. The structure is the network. The structure inside a complex processing node might consist of concurrent processes executing in parallel and communication through some combination of shared variables.

DATABASE DESIGN:
Planning the Database: The most important consideration in designing the database is how the information will be used.  Business activities that will use the database to perform.  Business rules that apply to these activities  Data wanted to maintain in the database

The main objectives of designing a database are    Data integration Data integrity Data independence

DATA INTEGRATION: In a database, information from several files is co-ordinate, accessed and operand upon as though it is single file.

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Logically, the information is centralized, physical, the data may be located facilities. Design Methodology: Design is concerned with identifying software components, specifying relationships among component, specifying software structure and providing a blue print for the implementation phase. Design consists of three types: 1. Architectural Design 2. Detail Design 3. External Design Architectural Design: Architectural Design involves identifying the software components, decoupling and decomposing them into processing modules and conceptual data structure and specifying relationships among the components.

Detailed Design: Detailed design is concerned with the details of how to package the processing modules and how to implement the processing algorithms, data structure and interconnection among modules and data structure. GUI based design: In order to have a better understanding over the system design, it is appropriate to know the actual designing in terms of the development platform and the way in which the GUI are designed to satisfy the requirements of the user. The analysis of the design aspects of this package is proposed External design. External design of software involves conceiving, planning and specifying the external observable characteristics in different devices connected though data communication

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of a software product. This includes reports and display formats. External design begins analysis phase it continues into the design phase. DATA INTEGRITY: Data integrity means storing all the data in single place and allow each application to access it. This approach results in more consistent, on update being sufficient to achieve a new record status for all the applications, which use it. This leads to less data redundancy, data items need not be duplicated, requirement.

DATA INDEPENDENCE: Data independence is the insulation of application programs from changing aspects of physical data organization. This objective seeks to allow changes in the content and organization of physical data without reprogramming of applications and to allow modifications to application programs without the reorganizing the physical data. Normalization: Data structuring is refined through a process called normalization.

Normalization is a formal process of developing data structures in a manner that eliminates decomposition redundancy and promotes integrity. of complex records into simple It is a step-by-step records to reduce a reduction in the direct access storage redundancy, inconsistencies and remove anomalies. There are several normal forms to be followed in normalization process. The most important and widely used are:     ONLINE LIBRARY BY M.SATHISH KUMAR Page 28 First Normal Form Second Normal Form Third Normal Form

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First Normal Form: A table is said to be in first normal form if the intersection of any column and row contains only value. Method: This is identifying a suitable identifier from the pool of normalized data. Remove any item that repeat within a single value of this key to another relation bringing with them the identifier key to form part of new composite key in the relation. Second Normal Form: For a table to be in the second normal form it should also be in the first normal form and the values in every column are functionally dependent on the complete primary key.

Method: Examine every column and section whether its value depend on the whole of the compound key or just some parts of it. Remove key. Third Normal Form: For a table to be in the third normal form transitively dependent on the primary key. Method: Examine every non-key column with every other non-key column. If the value of the non-key column depends on the other non-key column then remove the columns to separate table. it should be in the those that depend only on part of the key to a new table with that part as the primary

second normal form and the values in every non-key column are not

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De Normalization: The normalization process helps in reducing to a great extent but sometimes when information is required from more than one table, at a fast rate , it is desirable to have some degree of redundancy in table . Their deliberate introduction of redundancy for a highly improved performance is referred to as ” De Normalization” .

DATABASE TABLES:
1. QUARRIES: The QUARRES table can store quarries entered by user with unique ID (QID). It is stores unique quarries irrespective order of words and case of letters. 2. DOCUMENTS: The DOCUMENTS table can hold name of documents, which are in server with unique ID for every document. 3. WORDS: The WORDS table can store words, which are in documents. This table plays key role in creating index for documents. This table contains a unique ID and words column. Unique words can be stored in this table irrespective of case of letters. 4. RANKS: The RANKS table can hold rank and weight for each document with respect to query. This table contains four columns. QID and DID are refer QID of QUERRIES and DID of DOCUMENTS table respectively.

5. INDEX: The INDEX table helps to search engine while searching for documents, which are relate to query given by user. Simply it makes fast Searching. It contains two columns WID, DID refer WID of WORDS, DID of DOCUMENTS tables. 6. USERDETAILS: The USERDETAILS can hold details of users. Username, user-id, password etc.

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ENTITY RELATIONSHIP DIAGRAMS

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ABOUT THE SOFTWARE
INTRODUCTION: HTML stands for hyper text makeup language. It is a language used to create hypertext documents that have hyperlinks embedded in them. You can build web pages. It is only a formatting language and not a programming language. Hyperlinks are underlined or emphasized words or locations in a screen that leads to other documents, W W W is a global, Interactive, dynamic, cross Platform, graphical hypertext information system. The idea behind hypertext is that instead of reading text in rigid linear structure you can easily jump from one point to another. You can Navigate through the information based on your interest and preferences.

HYPERMEDIA HTML pages with audio and video files linked to them are called Hypermedia. HTML is platform independent.

HTML IS PLATFORM INDEPENDENT: If you can access internet, you can access WWW, Irrespective of your operating system and the operating system to the web server. All you require to view and unload the HTML files, which are on the WWW, are a browser and internet connection.

WEB IS DISTRIBUTED: The information on the WWW is distributed through out the world. You can access it with a few mouse clicks. You do not have to store it on your machine. Information on the Web is dynamically updateable. As the information is at the site where it is published, the people who publish it can change it any time. HTML is a language for describing structured documents, HTML describes the structures of documents – lists, headings, paragraphs Etc. Elements of web documents are labeled through the usage of HTML tags, It is the tags that describe the documents. Anything that is not a tag part of the Document itself.

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The Static Web

When the World Wide Web was born, it consisted of static Web sites. Web sites consisted of static documents (mostly HTML pages) that were accessible through Web servers. Users used Web browsers to access these Web sites. A Web browser communicated with a Web server over the Hyper Text Transfer Protocol (HTTP). Using an HTTP request, the browser communicated with the Web server and asked to get access to a certain document. The Web server managed a set of documents stored on a file system. When asked for a
document, it would retrieve it and return it within an HTTP response:

HTML DOES NOT DESCRIBE PAGE LAYOUT:

World for windows or lotus improve for example, have different styles for Headings, font, Size, and identification. HTML does not have all these. Based on the plat form , exact placement or appearance of any element will change. There may be or may not be fonts installed. By separating the structure of the document and its appearance, a program, that reads and understands HTML can make formatting decisions based on capabilities of the individual platform . In addition to providing the networking functions to retrieve documents, Web browsers are also HTML formatters.

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They parse and format documents and display them on the screen. Different rowsers show data differently.

ADVANTAGES : A HTML document is small and hence easy to send over the net. It is small because it does not include format information. HTML documents are cross platform compatible and device independent. You only need a HTML reliable browser to view them. Font names, locations Etc.. are required. Currently the standard fully supported is HTML 2.0 & HTML 3.0 is in use. It supports. Centered and right aligned text. Tables . Math equations Text and image alignment

JAVA
INTRODUCTION Java is an intercepted language. Though it bears a close resemblance to C++ , it is different from it in many ways. It is a smaller, portable, purely object oriented Language that eliminates many of the sources of bugs and complexities that are common with C Or C++ . JAVA FEATURES: Java is simple, Object Oriented, Intercepted, Robust, Secure Architecture neutral, Portable, has high performance, multi threaded and dynamics. It is easier To use Java because it’s syntax is similar to C and C++, more so when it eliminates components of C that causes bugs and memory leaks and hence a lot less debugging, Java provides a powerful Set of pre-tested libraries that give us the ability to use advanced features even with few lines of Code. OBJECT ORIENTED Java is an Object oriented programming Language that uses software objects called CLASESS and it is based on reusable, extensible code. This implies we can use Java’s classes, which are sets of variables and methods, as

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templates to create other Classes with added functionality without the need to write the code from Scratch. The Application can be made small and easy to develop if we plan the class hierarchy well. Robust: Java is Robust because, the language removes the use of pointers and The Java Runtime System manages the memory for us. Java gives us automatic bounds checking for arrays, so that they cannot reside in an address space which is not allocated for them. Automatic memory management is taken care of by the Garbage Collector.

Interpreted: Java is interpreted; hence the development cycle is much faster. Java needs to compile for a single, virtual machine and then the code can run on any machine that has JVM ported to it. Secure: Java is secure, so user can download Java programs from anywhere. Java provides extensible compile time checking followed by a multi layered level of runtime Checking.

Architecture Neutral: Java is architecture neutral, so user applications are portable across multiple platforms. Java’s Applications are written and compiled into Byte Code for JVM, Which emulates an actual hardware chip. The Java Interpreter installed at the client, so applications need not be written for various platforms separately converts byte Code to machine code. Java further ensures that the applications are the same on every platform by strictly defining the sizes of the basic data types and their behaviour. Dynamic: Java is Dynamic., so the applications are adapted to changing environments, Java’s architecture allows the user to dynamically load classes at runtime from any where on the network, which means that the user can add functionality to applications by simply linking in new classes.

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JDBC OVERVIEW
What is JDBC? JDBC is a Java TM API for executing SQL statements. It consists of a set of classes and interfaces written in the JAVA programming language that makes it easy to send SQL statements to virtually any relational database. In other words, with the JDBC API, it isn’t necessary to write one program to access a Sybase database, another program to access an Oracle database, another program to access an Informix database, and so on. One can write a single program using the JDBC API, and the program will be able to send SQL statements to the appropriate database. And, with a program written in the JAVA programming language, one doesn’t have to worry about writing different programs to run on different platforms. The combination of JAVA and JDBC lets a programmer write it once and run it anywhere. JAVA, being robust, secures, easy to use, easy to understand, and automatically downloadable on a network, is an excellent language basis for database applications. What is needed is a way for JAVA applications to talk to variety of different databases. JDBC is the mechanism for doing this. JDBC extends what you can do in JAVA.

For example, with JAVA and the JDBC API, it is possible to publish a web page containing an applet that uses information obtained from a remote database. Or an enterprise can use JDBC to connect all its employees (Even if they are using a conglomeration of Windows, Macintosh and Unix machines) to one or more internal databases via. An Internet. With more and more programmers using the JAVA programming language, the need for easy database access from JAVA is continuing to grow. MIS managers like the combination of JAVA and JDBC because it makes disseminating information easy and economical. Business can continue to use their installed databases and access information easily even if it is stored on different database management systems. Development time for new applications is short. Installation and version controls are greatly simplified. A programmer can write an application or an update once, put it on the server and everybody has access to the latest version and for business selling information services, JAVA and JDBC offers better way of getting out information updates to

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external customers. Various ways to use JDBC are discussed in. What Does JDBC Do? Simply put, JDBC makes it possible to do three things: Establishes connection to databases. Send SQL statements. Process the results. JDBC is a Low-level API and a base for Higher-Level API. JDBC is a “Low-level” interface, which means that it is used to invoke SQL commands directly. It works very well in this capacity and is easier to use than other database connectivity APIs, but it was designed also to be a base upon which to build higher-level interfaces and tools. A higher-level interface is “User-friendly”, using a more understandable or more convenient API that is translated behind the scenes into a Low level interface such as JDBC. So why not just use ODBC from Java?

The answer is that you can use ODBC from JA V A, but this is best done with the help of JDBC in the form of the JDBC-ODBC Bridge. The question now becomes “Why do you need JDBCT’ There are several answers to this question: 1. ODBC is not appropriate for direct use from Java because is uses a C interface. 2. Calls from Java to native C code have a number of drawbacks in the security, 1. implementation, robustness, and automatic probability of applications. A literal translation of the ODBC API into a Java API world not desirable. For example, Java has no pointers, and ODBC makes copious use from, including the notoriously error-prone generic pointer “void *”. You can think as JDBC as ODBC translated into an object-oriented interface that is natural for Java programmers. 2. ODBC is hard to learn. It mixes simple and advanced features together, and it has complex options even for simple queries. JDBC, on the other

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hand, was designed for a wide range of programmers and keeps simple things simple. 3. A Java API like JDBC is needed in order to enable an “all-Java” solution. When ODBC is used, the driver manager and drivers must be manually installed on every client machine. When the JDBC driver is written completely in JAVA, however, JDBC code is automatically installed, portable, and secure on all Java platforms from network computers to mainframes. In summary, the JDBC API is natural JAVA interface is to the basic SQL abstractions and concepts. It builds an odbc rather than starting from search, so programmers familiar with odbc will find it very easy to learn JDBC. JDBC retains the basic design features of ODBC; infarct, both interfaces are based on the x/Open SQL CU( call level interface).

The big difference is that JDBC builds on and reinforces the style and virtues of Java, and of course, it is easy to use. ADVANTAGES. Until now, the middle tier has typically been written in languages such as C or C++, which offer fast performance. However, with introduction of optimizing compilers, translating Java byte code into efficient machinespecific code, it is becoming practical to implement the middle tier in Java. This is a big plus, making it possible to take advantage of Java’s robustness, multi-threading and security features. SOL Conformance Structured Query Language(SQL) is the standard language for accessing relational databases. One area of difficulty is that almost most DBMSs(Database Management Systems) gives a standard form of SQL for basic functionality, they do not conform to the more recently defined standard SQL syntax or semantics for more advanced functionality.

For example, not all databases support stored procedures or outer joins, and those that do are not consistent with each other. It is hoped that the portion of SQL that is truly standard will expand to include more functionality. In the mean time, however, the JDBC API must support SQL as it is. One way the JDBC API deals with the problem is to allow any query string to be passed through to an underlying DBMS driver. This means that an application is iTee to use as much SQL functionality is desired, but it runs the risk of receiving an error on some DBMS. In fact an application query need not even be an SQL, or it may be a specialized derivation of SQL designed for specific DBMS(for document or image queries). For example, a second way JDBC deals with the problems of SQL conformance is to provide ODBC style escape clauses. Which are discussed in SQL Escape Syntax in Statement objects. This escape syntax allows a programmer to use SQL

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functionality item within a JDBC program. The ODBC API is a natural choice for Java developers because it offers easy database access for Java applications and applets. Because JDBC brings together Java and databases, the remainder of the topic gives a brief overview of each.

JDBC DRIVERS
The JDBC drivers that we are aware of at this time fit into one of four categories. 1. JDBC-ODBC bridge plus ODBC Driver: The JavaSoft bridge product provides JDBC access via ODBC drivers. Note that ODBC binary code and in many cases database client code must be loaded on each client machine that uses this driver. As a result, this kind of driver is more appropriate on a corporate network where client installations are not a major problem, or for applications server code written in Java in a three-tier architecture. 2. Native-Api partly – JAVA Driver: This kind of driver converts JDBC calls into calls on the client api for Oracle, sybase, Informix, DB2, or other DBMS. Note that, like the bridge driver this style of driver requires that some binary code be loaded on each client machine. 3. JDBC-Net all– JAVA Driver: This driver translates JDBC calls into a DBMS independent net protocol, which is then translated to a DBMS protocol by a server.

This net server middleware is able to connect its all-Java clients to many different databases. The specific protocol used depends on the vendor. In general, this is the most flexible JDBC alternative. It is likely that all vendors of this solution will provide products suitable for internet use. In order for these products to also support internet access, they must handle the additional requirements for security, access through fire walls, etc., that the web imposes. Several vendors are adding JDBC drivers to their existing database middleware products. 4. Native – Protocol all-Java Driver: This kind of driver converts JDBC calls into the network protocol used b: dbms’s directly. This allows a direct call from the client machine to the dbms server and is a practical solution for internet access. Since many of ONLINE LIBRARY BY M.SATHISH KUMAR Page 39

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these protocols are proprietary, the database vendors themselves will be the primary source. Several database vendors have these in progress. Eventually, we expect that categories 3 and 4 will be the preferred way to access databases from JDBc. Driver categories 1 and 2 are in term solutions where direct all-Java drivers are not yet available. Category 4 is in some sense the ideal; however, there are many cases where category 3 may be preferable: e.g., where a thin dbms in dependent client is desired, or if a dbms-independent protocol is standardized and implemented directly by many dbms vendors.

SERVLETS
Introduction:
The Java web server is JavaSoft’s own web Server. The Java web server is just a part of a larger framework, intended to provide you not just with a web server, but also with tools. To build customized network servers for any Internet or Intranet client/server system. Servlets are to a web server, how applets are to the browser. About Servlets: Servlets provide a Java-based solution used to address the problems currently associated with doing server-side programming, including inextensible scripting solutions, platform-specific APIs, and incomplete interfaces. Servlets are objects that conform to a specific interface that can be plugged into a Java-based server. Servlets are to the server-side what applets are to the client-side – object byte codes that can be dynamically loaded off the net. They differ from applets in that they are faceless objects (without graphics or a GUI component). They serve as platform independent, dynamically loadable, pluggable helper byte code objects on

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the server side that can be used to dynamically extend server-side functionality. For example, an HTTP Servlets can be used to generate dynamic HTML content. When you use Servlets to do dynamic content you get the following advantages:  They‟re faster and cleaner than CGI scripts  They use a standard API (the Servlets API)  They provide all the advantages of Java (run on a variety of servers

without needing to be rewritten). Attractiveness of Servlets: There are many features of Servlets that make them easy and attractive to use. These include:  Easily configured using the GUI-based Admin tool  Can be loaded and invoked from a local disk or remotely across the

network.
 Can be linked together, or chained, so that one Servlets can call another

Servlets, or several Servlets in sequence.
 Can be called dynamically from within HTML pages, using server-side

include tags.
 Are secure – even when downloading across the network, the Servlets security model and Servlets sandbox protect your system from unfriendly behavior.

Advantages of Servlet API One of the great advantages of the Servlet API is protocol independence. It assumes nothing about:  The protocol being used to transmit on the net

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 How it is loaded  The server environment it will be running in  These qualities are important, because it allows the Servlet API to be embedded in many different kinds of servers. There are other advantages to the Servlet API as well. These include:  It‟s extensible – you can inherit all your functionality from the base

classes made available to you.
 it’s simple, small, and easy to use.

Features of Servlets:
 Servlets are persistent. Servlet are loaded only by the web server and can

maintain services between requests.
 Servlets are fast. Since Servlets only need to be loaded once, they offer

much better performance over their CGI counterparts.
 Servlets are platform independent.  Servlets are extensible. Java is a robust, object-oriented programming

language, which easily can be extended to suit your needs
 Servlets are secure.  Servlets can be used with a variety of clients.

Loading Servlets: Servlets can be loaded from three places From a directory that is on the CLASSPATH. The CLASSPATH of classes reside. From the


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