What are the various components of J2EE application architecture?

1.	What are the various components of J2EE application architecture?
Answer» J2EE is made up of 3 main components (tiers) - Client tier, Middle tier, ENTERPRISE data tier as shown in the below image: Client Tier: This tier has programs and applications which interact with the user and they are generally located in different machines from the server. Here, different inputs are taken from the user and these requests are forwarded to the server for PROCESSING and the response will be sent back to the client. Middle Tier: This tier comprises of Web components and EJB containers. The web components are either servlet or JSP pages that process the request and generate the response. At the time of the application’s assembly, the client’s static HTML codes, programs and applets along with the server’s components are bundled within the web components. The EJB components are present for processing inputs from the user which are sent to the Enterprise Bean that is running in the BUSINESS tier. Enterprise Data Tier: This tier includes database servers, resource planning systems and various other data sources that are located on a separate machine which are accessed by different components by the business tier. Technologies like JPA, JDBC, Java transaction API, Java Connector Architecture etc are used in this tier.

Answer»

J2EE is made up of 3 main components (tiers) - Client tier, Middle tier, ENTERPRISE data tier as shown in the below image:

Client Tier: This tier has programs and applications which interact with the user and they are generally located in different machines from the server. Here, different inputs are taken from the user and these requests are forwarded to the server for PROCESSING and the response will be sent back to the client.
Middle Tier: This tier comprises of Web components and EJB containers. The web components are either servlet or JSP pages that process the request and generate the response. At the time of the application’s assembly, the client’s static HTML codes, programs and applets along with the server’s components are bundled within the web components. The EJB components are present for processing inputs from the user which are sent to the Enterprise Bean that is running in the BUSINESS tier.
Enterprise Data Tier: This tier includes database servers, resource planning systems and various other data sources that are located on a separate machine which are accessed by different components by the business tier. Technologies like JPA, JDBC, Java transaction API, Java Connector Architecture etc are used in this tier.

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