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J2ee web services(overview)
- 1. J2EE WEB-SERVICES BY PRAFULL JAIN 2016BCEX1056 SEC-B , VIITH SEM
- 2. LIST OF CONTENTS:- 1. Application servers 2. What is J2EE? 3. Main Technologies 4. Application Scenarios 5. J2EE APIs and Services 6. EJB – a closer look
- 3. APPLICATION SERVERS • In the beginning Centralized, non-distributed terminals mainframe terminals 3 In the 90’s, systems should be client- server
- 4. APPLICATION SERVERS 4 Today, enterprise applications use the multi-tier model “Multi-tier applications” have several independent components. An application server provides the infrastructure and services to run such applications Application server products can be separated into 3 categories: J2EE-based solutions Non-J2EE solutions (PHP, ColdFusion, Perl, etc.) And the Microsoft solution (ASP/COM and now .NET with ASP.NET, VB.NET, C#, etc.)
- 5. WHAT IS J2EE? It is a public specification that embodies several technologies Current version is 1.5 J2EE defines a model for developing multi-tier, web based, enterprise applications with distributed components J2EE BENEFITS High availability Scalability Integration with existing systems Freedom to choose vendors of application servers, tools, components Multi-platform
- 6. J2EE BENEFITS Flexibility of scenarios and support to several types of clients Programming productivity: Services allow developer to focus on business. Component development facilitates maintenance and reuse Enables deploy-time behaviors Supports division of labor
- 7. MAIN TECHNOLOGIES JavaServer Pages (JSP) Servlet Enterprise JavaBeans (EJB) JSPs, servlets and EJBs are application components. JSP Used for web pages with dynamic content Processes HTTP requests (non-blocking call-and-return) Accepts HTML tags, special JSP tags, and scriptlets of Java code Separates static content from presentation logic Can be created by web designer using HTML tools
- 8. SERVLET Used for web pages with dynamic content Processes HTTP requests (non-blocking call- and-return) Written in Java; uses print statements to render HTML Loaded into memory once and then called many times Provides APIs for session management EJB EJBs are distributed components used to implement business logic (no UI) Developer concentrates on business logic Availability, scalability, security, interoperability and integrability handled by the J2EE server Client of EJBs can be JSPs, servlets, other EJBs and external aplications
- 9. Copyright 2002 © Paulo Merson J2EE MULTI-TIER MODEL
- 10. J2EE Application Scenarios Multi-tier typicalapplication
- 11. J2EE Application Scenarios Stand-aloneclient
- 12. J2EE Application Scenarios Web-centricapplication
- 13. J2EE SERVICES AND APIS Java Message Service (JMS) Implicit invocation Communication is loosely coupled, reliable and asynchronous Supports 2 models: point-to-point publish/subscribe
- 14. JMS Point-to-point Destination is “queue”
- 15. JMS Publish-subscribe Destination is “topic”
- 16. J2EE SERVICES AND APIS JNDI - Naming and directory services Applications use JNDI to locate objects, such as environment entries, EJBs, datasources, message queues JNDI is implementation independent Underlying implementation varies: LDAP, DNS, DBMS, etc. Transaction service: Controls transactions automatically You can limit the transactions explicitly Or you can specify relationships between methods that make up a single transaction
- 17. J2EE SERVICES AND APIS Security Java Authentication and Authorization Service (JAAS) is the new (J2EE 1.3) standard for J2EE security Authentication via userid/password or digital certificates Role-based authorization limits access of users to resources (URLs, EJB methods) Embedded security realm J2EE Connector Architecture Integration to non-J2EE systems, such as mainframes and ERPs. Standard API to access different EIS (GlassFish Server) Vendors implement EIS-specific resource adapters
- 18. J2EE SERVICES AND APIS JDBC JavaMail Java API for XML Parsing (JAXP) Web services APIs
- 19. EJB – A CLOSER LOOK
- 20. HOME INTERFACE Methods to create, remove or locate EJB objects The home interface implementation is the home object (generated) The home object is a factory REMOTE INTERFACE Business methods available to clients The remote interface implementation is the EJB object (generated) The EJB object acts as a proxy to the EJB instance
- 21. Copyright 2002 © Paulo Merson 34
- 22. EJB – THE BIG PICTURE
- 23. EJB AT RUNTIME
- 24. TYPES OF EJB StateFul Statless SessionBean Entity Bean Message Driven Bean BMP CMP Enterprise Bean
- 25. SESSION BEAN Stateful session bean: Retains conversational state (data) on behalf of an individual client If state changed during this invocation, the same state will be available upon the following invocation Example: shopping cart Stateless session bean: Contains no user-specific data Business process that provides a generic service Container can pool stateless beans Example: shopping catalog
- 26. ENTITY BEAN Represents business data stored in a database persistent object Underlying data is normally one row of a table A primary key uniquely identifies each bean instance Allows shared access from multiple clients Can live past the duration of client’s session Example: shopping order Bean-managed persistence (BMP): bean developer writes JDBC code to access the database; allows better control for the developer Container-managed persistence (CMP): container generates all JDBC code to access the database; developer has less code to write, but also less control
- 27. MESSAGE-DRIVEN BEAN Message consumer for a JMS queue or topic Benefits from EJB container services that are not available to standard JMS consumers Has no home or remote interface Example: order processing – stock info
- 28. SOURCES & RESOURCES The J2EE Tutorial. Sun Microsystems www.java.sun.com/j2ee www.theserverside.com www.Wikipedia.com/j2ee www.javatpoint.com