1 Chapter 29 Web Technology and DBMSs Transparencies © Pearson Education Limited 1995, 2005.

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Chapter 29

Web Technology and DBMSs

Transparencies

© Pearson Education Limited 1995, 2005

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Chapter 29 - Objectives

Basics of Internet, Web, HTTP, HTML, URLs. Advantages and disadvantages of Web as a

database platform. Approaches for integrating databases into Web:

– Scripting Languages– Common Gateway Interface (CGI)– HTTP Cookies


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Chapter 29 - Objectives

– Extending the Web Server– Java, J2EE, JDBC, SQLJ, CMP, JDO, Servlets,

and JSP– Microsoft Web Platform: .NET, ASP, and ADO– Oracle Internet Platform.


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Introduction

Web most popular and powerful networked information system to date.

As architecture of Web was designed to be platform-independent, can significantly lower deployment and training costs.

Organizations using Web as strategic platform for innovative business solutions, in effect becoming Web-centric.


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Introduction

Many Web sites today are file-based where each Web document is stored in separate file.

For large sites, this can lead to significant management problems.

Also many Web sites now contain more dynamic information, such as product and pricing data.

Maintaining such data in both a database and in separate HTML files is problematic.

Accessing database directly from Web would be a better approach.


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Internet

Worldwide collection of interconnected networks.

Began in late ‘60s in ARPANET, a US DOD project, investigating how to build networks that could withstand partial outages.

Starting with a few nodes, Internet estimated to have over 945 million users by end of 2004.

2 billion users projected by 2010. About 3.5 billion documents on Internet (550

billion if intranets/extranets included).


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Intranet and Extranet

Intranet - Web site or group of sites belonging to an organization, accessible only by members of that organization.

Extranet - An intranet that is partially accessible to authorized outsiders.

Whereas intranet resides behind firewall and is accessible only to people who are members of same organization, extranet provides various levels of accessibility to outsiders.


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eCommerce and eBusiness

eCommerce - Customers can place and pay for orders via the business’s Web site.

eBusiness - Complete integration of Internet technology into economic infrastructure of the business.

Business-to-business transactions may reach $2.1 trillion in Europe and $7 trillion in US by 2006.

eCommerce may account for $12.8 trillion in worldwide corporate revenue by 2006 and could represent 18% of sales in the global economy.


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The Web

Hypermedia-based system that provides a simple ‘point and click’ means of browsing information on the Internet using hyperlinks.

Information presented on Web pages, which can contain text, graphics, pictures, sound, and video.

Can also contain hyperlinks to other Web pages, which allow users to navigate in a non-sequential way through information.

Web documents written using HTML.


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The Web

Web consists of network of computers that can act in two roles: – as servers, providing information; – as clients (browsers), requesting information.

Protocol that governs exchange of information between Web server and browser is HTTP and locations within documents identified as a URL.

Much of Web’s success is due to its simplicity and platform-independence.


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Basic Components of Web Environment


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HyperText Transfer Protocol (HTTP)

Protocol used to transfer Web pages through Internet.

Based on request-response paradigm: Connection - Client establishes connection with Web server.

Request - Client sends request to Web server.

Response - Web server sends response (HTML document)

to client.

Close - Connection closed by Web server.


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HyperText Transfer Protocol (HTTP)

HTTP/1.0 is stateless protocol - each connection is closed once server provides response.

This makes it difficult to support concept of a session that is essential to basic DBMS transactions.


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HyperText Markup Language (HTML)

Document formatting language used to design most Web pages.

A simple, yet powerful, platform-independent document language.

HTML is application of Standardized Generalized Markup Language (SGML), a system for defining structured document types and markup languages to represent instances of those document types.


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HyperText Markup Language (HTML)


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Uniform Resource Locators (URLs)

String of alphanumeric characters that represents location or address of a resource on Internet and how that resource should be accessed.

Defines uniquely where documents (resources) can be found.

Uniform Resource Identifiers (URIs) - generic set of all Internet resource names/addresses.

Uniform Resource Names (URNs) - persistent, location-independent name. Relies on name lookup services.


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Uniform Resource Locators (URLs)

URL consists of three basic parts: – protocol used for the connection,

– host name,

– path name on host where resource stored.

Can optionally specify:– port through which connection to host should be made,

– query string.

http://www.w3.org/Markup/MarkUp.html


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Static and Dynamic Web Pages

HTML document stored in file is static Web page.

Content of dynamic Web page is generated each time it is accessed.

Thus, dynamic Web page can:– respond to user input from browser; – be customized by and for each user.

Requires hypertext to be generated by servers. Need scripts that perform conversions from

different data formats into HTML ‘on-the-fly’.


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Web Services

Collection of functions packaged as single entity and published to network for use by other programs.

Web services are important paradigm in building applications and business processes for the integration of heterogeneous applications.

Based on open standards and focus on communication and collaboration among people and applications.

Unlike other Web-based applications, Web services have no user interface and are not targeted for browsers. Instead, consist of reusable software components designed to be consumed by other applications.


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Web Services – Technologies & Standards

eXtensible Markup Language (XML). SOAP (Simple Object Access Protocol) protocol, based

on XML, used for communication over Internet. WSDL (Web Services Description Language) protocol,

again based on XML, used to describe the Web service. UDDI (Universal Discovery, Description and

Integration) protocol used to register the Web service for prospective users.


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Web Services

Common example is stock quote facility, which receives a request for current price of a specified stock and responds with requested price.

Second example is Microsoft MapPoint Web service that allows high quality maps, driving directions, and other location information to be integrated into a user application, business process, or Web site.


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Requirements for Web-DBMS Integration

Ability to access valuable corporate data in a secure manner.

Data- and vendor-independent connectivity to allow freedom of choice in DBMS selection.

Ability to interface to database independent of any proprietary browser or Web server.

Connectivity solution that takes advantage of all the features of an organization’s DBMS.


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Open architecture to allow interoperability with a variety of systems and technologies. For example: – different Web servers; – Microsoft's (Distributed) Common Object Model

(DCOM/COM);– CORBA/IIOP (Internet Inter-ORB protocol);– Java/Remote Method Invocation (RMI);– XML;– Web services (SOAP, WSDL, UDDI).

Cost-effective solution that allows for scalability, growth, and changes in strategic directions, and helps reduce applications development costs.


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Support for transactions that span multiple HTTP requests.

Support for session- and application-based authentication.

Acceptable performance. Minimal administration overhead. Set of high-level productivity tools to allow

applications to be developed, maintained, and deployed with relative ease and speed.


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Advantages of Web-DBMS Approach

DBMS advantages Simplicity Platform independence Graphical User Interface Standardization Cross-platform support Transparent network access Scalable deployment Innovation


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Disadvantages of Web-DBMS Approach

Reliability Security Cost Scalability Limited functionality of HTML Statelessness Bandwidth Performance Immaturity of development tools


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Approaches to Integrating Web and DBMSs

Scripting Languages. Common Gateway Interface (CGI). HTTP Cookies. Extending the Web Server. Java, J2EE, JDBC, SQLJ, JDO, Servlets, and JSP. Microsoft Web Solution Platform: .NET, ASP,

and ADO. Oracle Internet Platform.


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Scripting Languages (JavaScript and VBScript)

Scripting languages can be used to extend browser and Web server with database functionality.

As script code is embedded in HTML, it is downloaded every time page is accessed.

Updating browser is simply a matter of changing Web document on server.

Some popular scripting languages are: JavaScript, VBScript, Perl, and PHP.

They are interpreted languages, not compiled, making it easy to create small applications.


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Common Gateway Interface (CGI)

Specification for transferring information between a Web server and a CGI program.

Server only intelligent enough to send documents and to tell browser what kind of document it is.

But server also knows how to launch other programs.

When server sees that URL points to a program (script), it executes script and sends back script’s output to browser as if it were a file.


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CGI - Environment


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CGI

CGI defines how scripts communicate with Web servers.

A CGI script is any script designed to accept and return data that conforms to the CGI specification.

Before server launches script, prepares number of environment variables representing current state of the server, who is requesting the information, and so on.

Script picks this up and reads STDIN.


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CGI

Then performs necessary processing and writes its output to STDOUT.

Script responsible for sending MIME header, which allows browser to differentiate between components.

CGI scripts can be written in almost any language, provided it supports reading and writing of an operating system’s environment variables.


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CGI

Four primary methods for passing information from browser to a CGI script:

– Passing parameters on the command line.

– Passing environment variables to CGI programs.

– Passing data to CGI programs via standard input.

– Using extra path information.


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CGI - Passing Parameters on Command Line


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CGI - Advantages

CGI is the de facto standard for interfacing Web servers with external applications.

Possibly most commonly used method for interfacing Web applications to data sources.

Advantages:– simplicity, – language independence, – Web server independence, – wide acceptance.


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CGI - Disadvantages

Communication between client and database server must always go through Web server.

Lack of efficiency and transaction support, and difficulty validating user input inherited from statelessness of HTTP protocol.

HTTP never intended for long exchanges or interactivity.

Server has to generate a new process or thread for each CGI script.

Security.


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HTTP Cookies

Cookies can make CGI scripts more interactive. Cookies are small text files stored on Web client. CGI script creates cookie and has Web server

send it to client’s browser to store on hard disk. Later, when client revisits Web site and uses a

CGI script that requests this cookie, client’s browser sends information stored in the cookie.

Cookies can be used to store registration information or preferences (e.g. for virtual shopping cart).

However, not all browsers support cookies. © Pearson Education Limited 1995, 2005

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Extending the Web Server

To overcome limitations of CGI, many servers provide an API that adds functionality to server.

Two of main APIs are Netscape’s NSAPI and Microsoft’s ISAPI.

Scripts are loaded in as part of the server, giving back-end applications full access to all the I/O functions of server.

One copy of application is loaded and shared between multiple requests to server.


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Extending the Web Server

Approach more complex than CGI, possibly requiring specialized programmers.

Can provide very flexible and powerful solution. API extensions can provide same functionality as

a CGI program, but as API runs as part of the server, API approach can perform significantly better than CGI.

Extending Web server is potentially dangerous, since server executable is being changed.


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Comparison of CGI and API

CGI and API both extend capabilities of server. CGI scripts run in environment created by

Web server program. Scripts only execute once Web server interprets

request from browser, then returns results back to the server.

API approach not nearly so limited in its ability to communicate.

API-based extensions are loaded into same address space as Web server.


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Java

Proprietary language developed by Sun. Originally intended to support environment of

networked machines and embedded systems. Now, Java is rapidly becoming de facto language

for Web computing. Interesting because of its potential for building

Web applications (applets) and server applications (servlets).


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Java

‘A simple, object-oriented, distributed, interpreted, robust, secure, architecture neutral, portable, high-performance, multi-threaded and dynamic language’.

Has a machine-independent target architecture, the Java Virtual Machine (JVM).

Since almost every Web browser vendor has already licensed Java and implemented an embedded JVM, Java applications can currently be deployed on most end-user platforms.


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Java


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Java

Before Java application can be executed, it must first be loaded into memory.

Done by Class Loader, which takes ‘.class’ file(s) containing bytecodes and transfers it into memory.

Class file can be loaded from local hard drive or downloaded from network.

Finally, bytecodes must be verified to ensure that they are valid and do not violate Java’s security restrictions.


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Java

Loosely speaking, Java is a ‘safe’ C++. Safety features include strong static type

checking, automatic garbage collection, and absence of machine pointers at language level.

Safety is central design goal: ability to safely transmit Java code across Internet.

Security is also integral part of Java’s design - sandbox ensures untrusted application cannot gain access to system resources.


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Java 2 Platform

In mid-1999, Sun announced it would pursue a distinct and integrated Java enterprise platform:– J2ME: aimed at embedded and consumer-electronics

platforms.– J2SE: aimed at typical desktop and workstation

environments. Serves as foundation for J2EE and Web services.

– J2EE: aimed at robust, scalable, multiuser, and secure enterprise applications.

J2EE was designed to simplify complex problems with development, deployment, and management of multi-tier enterprise applications.


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Java 2 Platform


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Java 2 Platform Cornerstone of J2EE is Enterprise

JavaBeans (EJB), a standard for building server-side components in Java.

Three types of EJB components:– EJB Session Beans, components implementing

business logic, business rules, and workflow. – EJB Message-Driven Beans (MDBs), which process

messages sent by clients, EJBs, or other J2EE components.

– EJB Entity Beans, components encapsulating some data contained by the enterprise. Entity Beans are persistent.


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Java 2 Platform Two types of entity beans:

– Bean-Managed Persistence (BMP), which requires developer to write code top make bean persist using an API such as JDBC or SQLJ.

– Container-Managed Persistence (CMP), where persistence is provided automatically by container.

Discuss 5 ways to access a database: JDBC, SQLJ, CMP, JDO, and JSP.


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JDBC

Modeled after ODBC, JDBC API supports basic SQL functionality.

With JDBC, Java can be used as host language for writing database applications.

On top of JDBC, higher-level APIs can be built. Currently, two types of higher-level APIs:

– An embedded SQL for Java (e.g. SQLJ). – A direct mapping of relational database tables to Java

classes (e.g. TopLink from Oracle).


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JDBC

JDBC API consists of two main interfaces: an API for application writers, and a lower-level driver API for driver writers.

Applications and applets can access databases using:– ODBC drivers and existing database client

libraries;– JDBC API with pure Java JDBC drivers.


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JDBC


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JDBC - Advantages/Disadvantages

Advantage of using ODBC drivers is that they are a de facto standard for PC database access, and are available for many DBMSs, for very low price.

Disadvantages with this approach:– Non-pure JDBC driver will not necessarily work with

a Web browser.– Currently downloaded applet can connect only to

database located on host machine.– Deployment costs increase.


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SQLJ

Another JDBC-based approach uses Java with static embedded SQL.

SQLJ comprises a set of clauses that extend Java to include SQL constructs as statements and expressions.

SQLJ translator transforms SQLJ clauses into standard Java code that accesses database through a CLI.


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Comparison of JDBC and SQLJ

SQLJ is based on static embedded SQL while JDBC is based on dynamic SQL.

Thus, SQLJ facilitates static analysis for syntax checking, type checking, and schema checking, which may help produce more reliable programs at loss of some functionality.

It also potentially allows DBMS to generate an execution strategy for the query, thereby improving performance of the query.


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Comparison of JDBC and SQLJ

JDBC is low-level middleware tool with features to interface Java application with RDBMS.

Developers need to design relational schema to which they will map Java objects, and write code to map Java objects to rows of relations.

Problems: – need to be aware of two different paradigms (object

and relational);

– need to design relational schema to map onto object design;

– need to write mapping code.


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EJBs

EJBs have 3 elements in common:

– an indirection mechanism;

– a bean implementation;

– a deployment description. With indirection mechanism clients do not invoke EJB

methods directly. Session and entity beans provide access to their

operations via interfaces. home interface defines methods that manage lifecycle of

a bean. The corresponding server-side implementation classes are generated at deployment time.


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EJBs

To provide access to other operations, bean can expose a local interface (if client and bean are colocated), a remote interface, or both.

Local interfaces expose methods to clients running in same container or JVM.

Remote interfaces make methods available to clients no matter where deployed.

When a client invokes create() method (which returns an interface) on home interface, EJB container calls ejbCreate() to instantiate bean, at which point client can access bean through remote or local interface returned by create().


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EJBs


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EJBs

Bean implementation is a Java class that implements business logic defined in remote interface.

Transactional semantics are described declaratively and captured in the deployment descriptor.

Deployment descriptor, written in XML, lists a bean’s properties and elements, which may include:– home interface, remote interface, local interface;– Web service endpoint interface, – bean implementation class, – JNDI name for bean, transaction attributes,

security attributes, and per-method descriptors.


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Container-Managed Persistence (CMP)

Instead of writing Java code to implement BMP, CMP is defined declaratively in deployment descriptor.

At runtime, container manages bean’s data by interacting with data source designated in deployment descriptor.

Following steps need to be followed for CMP:– Define CMP fields in local interface.– Define CMP fields in entity bean class implementation.– Define CMP fields in deployment descriptor.– Define PK field and its type in deployment descriptor.


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Container-Managed Relationships (CMR)

EJB container can manage relationships between entity beans and session beans.

Relationships have a multiplicity, which can be 1:1, 1:M, or M:M, and a direction, which can be unidirectional or bidirectional.

Local interfaces provide foundation for CMR. With CMR, beans use local interfaces to maintain

relationships with other beans. For example, a Staff bean can use collection of

PropertyForRent local interfaces to maintain a 1:M relationship

Container can also manage referential integrity.


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Container-Managed Relationships (CMR)

CMR relationships are described declaratively in deployment descriptor file outside enterprise-beans element.

Need to specify both beans involved in relationship.

Relationship is defined in ejb-relations element, with each role defined in ejb-relationship-role element.

When bean is deployed, the container provider’s tools parse deployment descriptor and generate code to implement underlying classes.


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EJB Query Language (EJB-QL)

Used to define queries for entity beans that operate with CMP. EJB-QL can express queries for two different styles of operations:– finder methods, which allow results of an EJB-QL query

to be used by clients of the entity bean. Finder methods are defined in home interface.

– select methods, which find objects or values related to state of an entity bean without exposing results to client. Select methods are defined in entity bean class.

An object-based approach for defining queries against persistent store; conceptually similar to SQL.


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As with CMP and CMR fields, queries are defined in the deployment descriptor.

EJB container is responsible for translating EJB-QL queries into query language of persistent store, resulting in query methods that are more flexible.

<query><query-method>

<method-name>findAll</method-name><method-params></method-params>

</query-method><result-type-mapping>Local</result-type-mapping>

<ejb-ql><![CDATA[SELECT OBJECT(s) FROM Staff s]]></ejb-ql></query>


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<query>

<query-method>

<method-name>findByStaffName</method-name>

<method-params>java.lang.String</method-params>

</query-method>

<result-type-mapping>Local</result-type-mapping>

<ejb-ql><![CDATA[SELECT OBJECT(s)

FROM Staff s WHERE s.name = ?1]]>

</ejb-ql>

</query> © Pearson Education Limited 1995, 2005

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Java Data Objects (JDO)

ODMG submitted their Java binding to Java Community Process as basis of JDO. Development of JDO had two major aims:

– To provide standard interface between application objects and data sources, such as relational databases, XML databases, legacy databases, and file systems.

– To provide developers with a transparent Java-centric mechanism for working with persistent data to simplify application development. (Aim of JDO was to reduce need to explicitly code such things as SQL statements and transaction management into applications).


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Java Data Objects (JDO) - Interfaces

PersistenceCapable makes a Java class capable of being persisted by a persistence manager. Every class whose instances can be managed by a JDO PersistenceManager must implement this interface.

Most JDO implementations provide an enhancer that transparently adds code to implement this interface to each persistent class.

The interface defines methods that allow an application to examine runtime state of an instance and to get its associated PersistenceManager if it has one.

PersistenceManagerFactory obtains PersistenceManager instances. PMF instances can be configured and serialized for later use.


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Java Data Objects (JDO) - Interfaces

PersistenceManager contains methods to manage the lifecycle of PersistenceCapable instances and is also the factory for Query and Transaction instances.

A PersistenceManager instance supports one transaction at a time and uses one connection to the underlying data source at a time.

Query allows applications to obtain persistent instances from data source. Can be many Query instances associated with a PersistenceManager and multiple queries may be designated for simultaneous execution.

This interface is implemented by each JDO vendor to translate expressions in JDOQL into native query language of data store.


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Java Data Objects (JDO) – Interfaces and Classes

Extent is a logical view of all objects of a particular class that exist in the data source.

Extents are obtained from a PersistenceManager and can be configured to also include subclasses.

Extent has two possible uses: (a) to iterate over all instances of a class; (b) to execute a query in the data source over all instances of a particular class.

Transaction contains methods to mark start/end of transactions.

JDOHelper class defines static methods that allow a JDO-aware application to examine runtime state of instances and to get its associated PersistenceManager if it has one.


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JDO – Creating Persistent Classes

1. Ensure each class has a no-arg constructor. If class has no constructors defined, complier automatically generates a no-arg constructor; otherwise, developer will need to specify one.

2. Create a JDO metadata file to identify the persistent classes. The JDO metadata file is expressed as an XML document.

3. Enhance classes so that they can be used in a JDO runtime environment. JDO specification describes a number of ways that classes can be enhanced, however, most common way is using an enhancer program that reads a set of .class files and JDO metadata file and creates new .class files that have been enhanced to run in a JDO environment.


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JDO – Reachability-based Persistence JDO supports reachability-based persistence. Thus, any transient instance of a persistent class will

become persistent at commit if it is reachable, directly or indirectly, by a persistent instance.

Instances are reachable through either a reference or collection of references.

Reachability algorithm is applied to all persistent instances transitively through all their references to instances in memory, causing the complete closure to become persistent.

Allows developers to construct complex object graphs in memory and make them persistent simply by creating a reference to graph from a persistent instance.

Instances have to be explicitly deleted.


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JDO Query Language (JDOQL)

Data source-neutral query language based on Java boolean expressions.

Syntax is same as standard Java syntax, with a few exceptions.

A Query object is used to find persistent objects matching certain criteria. A Query is obtained through one of newQuery() methods of PersistenceManager.

Basic JDOQL query has following 3 components: – a candidate class (usually a persistent class); – a candidate collection containing persistent objects

(usually an Extent); – a filter, a boolean expression in a Java-like syntax.


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JDO Query Language (JDOQL)

Query result is a subcollection of candidate collection containing only those instances of candidate class that satisfy filter.

Queries can include optional parameter declarations that act as placeholders in filter string, variable declarations, imports, and ordering expressions.Query query = pm.newQuery(PropertyForRent.class,

“this.rent < 400”);

Collection result = (Collection) query.execute();


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Java Servlets

Servlets are programs that run on Java-enabled Web server and build Web pages, analogous to CGI.

Have a number of advantages over CGI:– improved performance;

– portability;

– extensibility;

– simpler session management;

– improved security and reliability.


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Java Server Pages (JSP)

Java-based server-side scripting language that allows static HTML to be mixed with dynamically-generated HTML.

Compiled into Java servlet and processed by a Java-enabled Web server (JSP works with most Web servers).

Since servlet is compiled, performance is improved.


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Java Web Services – Document-Oriented

Deal directly with processing XML documents. Java API for XML Processing (JAXP), processes

XML documents using various parsers and transformations. JAXP supports both SAX and DOM. Also supports the XSLT.

Java Architecture for XML Binding (JAXB), processes XML documents using schema-derived JavaBeans component classes. JAXB provides methods for unmarshalling an XML instance document into a tree of Java objects, and marshalling tree back into an XML document.


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Java Web Services – Document-Oriented

SOAP with Attachments API for Java (SAAJ), provides standard way to send XML documents over Internet from Java platform. Based on SOAP 1.1 and SOAP with Attachments, which define a basic framework for exchanging XML messages.


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Java Web Services – Procedure-Oriented

Java API for XML-based RPC (JAX-RPC), sends SOAP method calls to remote clients over Internet and receives results.

Client written in language other than Java can access a Web service developed and deployed on Java platform.

Also, client written in Java can communicate with service developed and deployed using some other platform.


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Java Web Services – Procedure-Oriented

Java API for XML Registries (JAXR), provides standard way to access business registries and share information.

JAXR gives Java developers a uniform way to use business registries based on open standards (such as ebXML) or industry consortium-led specifications (such as UDDI).


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Microsoft Web Platform - .NET

“Software is delivered as a service, accessible by any device, any time, any place, and is fully programmable and personalizable.”

Contains various tools, services, and technologies, such as:– Windows 2000, – Exchange Server, – Visual Studio, – HTML/XML, – scripting languages, – components (Java, ActiveX).


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Object Linking and Embedding for DataBases (OLE DB)

Microsoft has defined set of data objects, collectively known as OLE DB.

Allows OLE-oriented applications to share and manipulate sets of data as objects.

OLE DB is an object-oriented specification based on C++ API.

Components can be treated as data consumers and data providers. Consumers take data from OLE DB interfaces and providers expose OLE DB interfaces.


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OLE DB Architecture


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Active Server Pages (ASP)

ASP is programming model that allows dynamic, interactive Web pages to be created on server.

ASP provides flexibility of CGI, without performance overhead discussed previously.

ASP runs in-process with the server, and is optimized to handle large volume of users.

When an ‘.asp’ file is requested, Web server calls ASP, which reads requested file, executes any commands, and sends generated HTML page back to browser.


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Active Server Pages (ASP)


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ActiveX Data Objects (ADO)

Programming extension of ASP supported by Microsoft IIS for database connectivity.

Supports following key features:– Independently-created objects.– Support for stored procedures.– Support for different cursor types.– Batch updating.– Support for limits on number of returned rows.– Support for multiple recordsets.

Designed as an easy-to-use interface to OLE DB.


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ADO Object Model


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Remote Data Services (RDS)

Microsoft technology for client-side database manipulation across Internet.

Still uses ADO on server-side to execute query and return recordset to client, which can then execute other queries on recordset.

RDS provides mechanism to send updated records back to server.

A disconnected recordset model.


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Comparison of ASP and JSP

Both designed to enable developers to separate page design from programming logic through use of callable components.

Differences:– JSP is essentially platform and server independent

whereas ASP primarily restricted to MS Windows-based platforms.

– JSP perhaps more extensible as JSP developers can extend the JSP tags available.

– JSP components are reusable across platforms.– JSP benefits from in-built Java security model.


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Microsoft .NET

Number of limitations with Microsoft’s platform:– a number of languages supported with different

programming models (J2EE composed solely of Java);

– no automatic state management;

– relatively simple user interfaces for Web compared to traditional Windows user interfaces;

– need to abstract operating system (Windows API difficult to program).

Next, and current, evolution in Microsoft’s Web solution strategy was development of .NET.


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Microsoft .NET

Various tools, services, technologies in .NET:– Windows Server, – BizTalk Server (to build XML-based business processes

across applications and organizations),– Commerce Server (to build scalable e-Commerce

solutions), – Application Center (to deploy and manage scalable Web

applications), – Mobile Information Server (to support handheld

devices), – SQL Server,– Microsoft Visual Studio .NET – Microsoft .NET Framework (CLR + Class Library).


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.NET Framework


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.NET – Common Language Runtime

An execution engine that loads, executes, and manages code compiled into an intermediate bytecode format - Microsoft Intermediate Language (MSIL) - analogous to Java bytecodes.

Not interpreted but compiled to native binary format before execution by a JIT compiler built into CLR.

Allows one language to call another, and even inherit and modify objects from another language.


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.NET – Common Language Runtime

Provides number of services such as memory management, code and thread execution, uniform error handling, and security.

Enforces strict type-and-code-verification system called common type system (CTS), which contains range of pre-built data types representing both simple data types for objects such as numbers and text values, and more complex data types for developing user interfaces, data systems, file management, graphics, and Internet services.

Also supports side-by-side execution allowing application to run on single computer that has multiple versions of .NET Framework installed, without application being affected.


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.NET Framework Class Library Collection of reusable classes, interfaces, and types that

integrate with CLR providing standard functionality such as:– string management, input/output, security management,– network communications, thread management, – user interface design features, – database access and manipulation.

3 main components:– Windows Forms to support user interface development.– ASP.NET to support development of Web applications

and Web services. Reengineered version of ASP to improve performance and scalability.

– ADO.NET to help applications connect to databases.


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ADO.NET

Designed to address 3 main weaknesses with ADO:– providing a disconnected data access model required for

Web;

– providing compatibility with .NET Framework class library;

– providing extensive support for XML.

Different from connected style of programming that existed in traditional 2-tier C-S architecture, where connection was held open for duration of program’s lifetime and no special handling of state was required.


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ADO.NET

Also ADO data model is primarily relational and could not easily handle XML with a data model that is heterogeneous and hierarchical.

Recognizing that ADO was a mature technology and widely used, ADO has been retained in the .NET Framework, accessible through the .NET COM interoperability services.

Two main layers:

– a connected layer (similar to ADO);

– a disconnected layer, the DataSet (providing a similar functionality to RDS).


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ADO.NET


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ADO.NET Object Model


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ADO.NET Main replacements for ADO Recordset are:

– DataAdapter, acts as bridge between vendor-dependent data source and vendor-neutral DataSet. While data source may be RDB, may also be an XML document.

– DataReader, provides connected, forward-only, read-only stream of data from data source. A DataReader can be used independently of a DataSet for increased performance.

– DataSet, provides disconnected copies of records from data source. DataSet stores records from one or more tables in memory without holding a connection to the data source, but unlike RDS DataSet maintains information on relationships between tables and constraints.


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ADO.NET

Several ways a DataSet can be used:

– user can create DataTable, DataRelation, and Constraint within DataSet and populate table with data programmatically.

– user can populate DataSet with data from existing relational data source using a DataAdapter.

– contents of DataSet can be loaded from an XML stream or document, which can be either data, XML schema information, or both.

Also, a DataSet can be made persistent using XML (with or without a corresponding XML Schema).


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Microsoft Web Services

.NET Framework built on number of standards to promote interoperability with non-Microsoft solutions.

For example, Visual Studio .NET automatically creates necessary XML and SOAP interfaces required to turn application into a Web service.

In addition, .NET Framework provides set of classes that conform to all the underlying communication standards, such as SOAP, WSDL, and XML.

Microsoft UDDI SDK enables developers to add UDDI functionality to development tools, installation programs, and any other software that needs to register or locate and bind remote Web services.


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Microsoft Access and Web Page Generation

Access provides wizards for automatically generating HTML/XML:– Static pages: user can export data to HTML format. – Dynamic pages using ASP: user can export data to an

‘asp’ file on Web server.– Dynamic pages using HTX/IDC files: user can export

data to HTX/IDC files on server. – Dynamic pages using data access pages: data access

pages are Web pages bound directly to data in the database. Can be used like Access forms, except pages are stored as external files.

– XML: data can be output as an XML document along with associated schema and an XSL file.


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Oracle Internet Platform

Comprises Oracle Application Server and Oracle DBMS.

It is n-tier architecture based on industry standards such as:– HTTP and HTML/XML for Web enablement.– Java, J2EE, EJB, JDBC, and SQLJ for database

connectivity, Java servlets, and JSP. Also supports JNDI and stored Java procedures.

– OMG’s CORBA technology.– IIOP for object interoperability and RMI. – Web services: SOAP, WSDL, UDDI, ebXML,

WebDav, LDAP.


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Oracle Internet Platform


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Oracle Application Server (OracleAS)

A reliable, scalable, secure, middle-tier application server designed to support eBusiness.

Currently available in three versions:– Java Edition: lightweight Web server with minimal

application support;– Standard Edition: for medium to large Web sites

that handle large volume of transactions;– Enterprise Edition: Standard Edition + extras.


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Communication Services

Handles all incoming requests received by OracleAS, some processed by Oracle HTTP Server and some by other areas of OracleAS.

Oracle HTTP Server is extended version of Apache Server.


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Oracle HTTP Server Modules (mods)

Oracle has enhanced several of Apache mods, and has added Oracle-specific ones; e.g.: – mod_oc4j, routes HTTP requests for J2EE to

OracleAS Containers for J2EE (OC4J);

– mod_plsql, routes requests for stored procedures to database server;

– mod_fastcgi, enhanced version of CGI that runs programs in pre-spawned process;

– mod_oradav, provides support for WebDAV;

– mod_ossl, provides standard S-HTTP;

– mod_osso, enables transparent single sign-on.


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OracleAS Containers for J2EE (OC4J)

A fully compliant J2EE 1.3 server. Runs on J2SE and executes and manages J2EE

application components such as:– Servlets Servlet container provided that manages

execution of Web components and J2EE applications. – JSPs JSP translator provided to convert JSP files into

Java source that container can then compile and execute as a servlet.

– EJBs EJB container provided that manages execution of EJBs for J2EE applications. Container has configurable settings that customize the underlying support , such as security, transaction management, JNDI lookups, and remote connectivity. Container also manages EJB lifecycles, database connection resource pooling, data persistence, and access to J2EE APIs.


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OracleAS Containers for J2EE (OC4J)

OracleAS supports both JDBC and SQLJ database access mechanisms, and provides following drivers:– Oracle JDBC drivers, for use with Oracle database.

Have extensions to support Oracle-specific datatypes and to enhance their performance.

– J2EE Connectors, part of J2EE platform, provide a Java-based solution for connecting various application servers and EISs.

– DataDirect Connect Type 4 JDBC drivers, for connecting to non-Oracle databases.


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Business Components for Java (BC4J)

A Java and XML framework that enables development, deployment, and customization of multi-tier database applications from reusable business components.

Application developers can use BC4J to author and test business logic in components that automatically integrate with databases, reuse business logic through SQL-based views, and access/update these views from servlets, JSP, and Java Swing clients.

Applications can be deployed as either EJB Session Beans or CORBA objects on OracleAS.


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Presentation Services

These services deliver dynamic content to client browsers, supporting servlets, JSP, Perl/CGI scripts, PL/SQL pages, forms, and business intelligence. – Oracle Forms Services, to run Oracle Forms over

Internet;

– OracleJSP, an implementation of Sun’s JSP;

– Oracle PSP (PL/SQL Server Pages), analogous to JSP, but uses PL/SQL rather than Java for the server-side scripting.

– Perl Interpreter, a persistent Perl runtime embedded in Oracle HTTP Server.


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Web Services and XML Support

OracleAS provides facilities for developing, deploying, and managing Web services; e.g.: – Web services can be developed using stateless and

stateful Java classes, stateless session EJBs, and stateless PL/SQL stored procedures.

– Web Service HTML/XML Streams Processing Wizard assists developers in creating an EJB whose methods access and process HTML or XML streams.

– Web services can be integrated into both enterprise and wireless portals, other Web services, databases, legacy systems, and applications.

– OracleAS supports SOAP, WSDL, and UDDI.© Pearson Education Limited 1995, 2005

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TopLink

A persistence framework that includes an object-relational mapping mechanism for storing Java objects and EJBs in a RDB.

Provides solution to address complex differences between Java objects and RDBs and enables applications to store persistent Java objects in any RDB supported by a JDBC driver.

Includes Mapping Workbench, a visual tool to map any object model to any relational schema.


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Oracle Portal

A portal is Web-based application that provides a common, integrated entry point for accessing dissimilar data types on a single Web page.

A portal is divided into a number of portlets. Oracle Portal provides a number of tools to

generate and customize portals and portlets.


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Oracle Wireless

Provides services and tools for delivering information and applications to mobile devices.

Includes Multi-Channel Server (MCS) that supports development of applications that are accessible from multiple channels including wireless browsers, voice, and messaging.

MCS automatically translates applications written in Oracle Wireless XML, XHTML Mobile Profile, or XHTML+XForms for any device and network.

Also allows portal sites to be created that use Web pages, Java applications, and XML-based applications.


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Business Intelligence

Functions to track, extract, and analyze business intelligence to support strategic decision-making:– Oracle Reports Services enable users to run Oracle

Reports over Internet.

– Oracle Discoverer allows users to produce queries, reports, and analysis of information from databases, OLTP systems, and data warehouses using a Web browser.

– Oracle Clickstream provides services to capture and analyze aggregate information about Web site usage.

– Oracle Personalization enables users to track activity of specific user and personalize information for that user.


1 Chapter 29 Web Technology and DBMSs Transparencies © Pearson Education Limited 1995, 2005.

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