- Java EE 5 (J2EE 5) uses XML deployment descriptors for the configuration of the web-applications and web-components.
- What Java EE provides? It provides the internal framework/structure/system level capability/system-level infrastructure to support large enterprise level applications with features like distributed database, distributed computing , security, and transaction management.
- J2EE also provides specifications for Containers, Connectors, Interfaces, Communications among different components for enterprise applications
- J2EE is J2SE based, it supports all of J2SE
- J2EE in addition to Swing and AWT introduces JSF for user interface creations
- Sun provides the J2EE specifications and a reference implementation. Anyone can re-implement the complete specification. Hence, if you develop applications based on the core J2EE, it should be compatible across different vendors who later re-implemented J2EE.
- However, J2EE does not cover 100% of the requirements of all types of enterprise applications, hence vendors usually add values/extra features to their implementations.
- J2EE provides multi-tier application development
- Elements of J2EE
- Clients: Fat Clients: A console application, and JFC, Swing, AWT based GUI applications. Thin clients: Browser based client applications
- Servers: Connect client components to the business logic.
- Server side components: Web-Components: JSPs, Servlets. Business components: EJBs.
- J2EE containers provide the support/framework/infrastructure for these server side components. Web Container contains JSPs/Servlets. EJB Container contains EJBs
- Some concepts in J2EE
- Containers, JSF, JDBC, XML Support, Web-Services, Transaction Management, Security
- Servlet: Mostly for Processing/calculations: From The clients, you can refer to a Servlet for example in HTML Form Actions. The Servlet runs in the server, does required processing and returns HTML web-page to the clients.
- JSP: Mostly for user interfaces, can also include processing using Java codes
- JSF: JSF is used to create rich user interfaces in conjunction with JSPs and Servlets.
- JSF provides API based server side user interface creation
- JDBC provides APIs to access relational databases. Enterprise applications very often will store information in databases. JDBC helps to access these information.
- EJBs evolved on RMI’s limitations to support enterprise applications. EJB components contain business logic.
- EJBs are of three types: entity beans, session beans, message beans
- J2EE 5 XML Support Technologies
- JAXP: DOM based processing. SAX: Stream based processing
- JAXB: Mapping between XML and Java classes
- JAXR: XML Registries
- JAXM for messaging
- JAX-RPC: XML based RPC
- JAXR, JAXM, and JAX-RPC: provide support for SOAP and web-services
- Web-services: Here functions/operations are provided as web-based services. Others can call and make use of these services. Great for B2B communications and integrations.
- Web-services: Related concepts: WSDL: Describes the services provided – Web Service Description Language. Service Registries such as ebXML, UDDI. JAXR API can access these registries. SOAP: The protocol for communications (web-services).
- Transaction Management: Java EE including EJBs provides transaction management support.
- J2EE also provides security supports such as role-based authorization, both declarative and programmatic securities.
From: http://sitestree.com/?p=4990
Categories:Java Short Notes
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Post Data:2011-02-12 03:58:54
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