Client and Server Design J2EE Steps In

What now? At this point, you understand how to design servers and how to design clients But how do you put them together? Where do you draw the line? What goes in the client and what goes in the server? How many servers? How many forms of client?

Difficult Questions Every imaginable design is used Focus first on the most prevalent The evolution was just that Consider –distributed for redundancy and scalability –objects for reusability and adaptability –web to insulate from the platform (os/hardware)

Incremental Incremental design/development is one of the tenets of design in a software system. Using an environment which does as much for you as possible is a desirable situation (within the parameters of cost) Buy components, assemble and integrate

Problems of Scaling an App communication overhead delay in accessing servers issues of priority and fairness synchronization running on different platforms –based on USER needs Multiple Clients

Problems of Scaling an App need for independence from client variety of client demands scalability transparency to client hardware based on –performance –infrastructure needs (Multiple) Servers

Problems of Scaling an App transaction service (commit/rollback) security load balancing thread management persistence middleware accounting and logging migrating from legacy systems System needs

Standard Components User interface: GUI/WEB Database/Persistence AI Communications Multimedia

Standard Components and Middleware Lots of examples –Databases –GUIs –Objects Problem with all of these is that they are typically platform or vendor specific An example follows

No Middleware OpenOracle() … OpenMySQL() … ORACLE MySQL Code must be changed to migrate to a new DB

Middleware OpenOracle() ORACLE Oracle Driver OpenMySQL() MySQL MySQL Driver Database Middleware OpenDB()

Middleware w/ODBC OpenSQL() SQL SQL Driver OpenAccess() Access Access Driver Microsoft -> ODBC OpenDB()

Middleware BDE and ODBC OpenOracle() ORACLE ODBC Oracle Driver OpenDB() OpenParadox() Paradox Paradox Driver DBOpen() BDE BDE to ODBC Driver NOT PERFECT!

How do we get here? STANDARDIZATION! We got tired of being unproductive. Companies realized losing a little flexibility could save lots of money Organizations cooperated They saw what standardization could do –OS, languages, GUIs, SQL –had the guts to open source

Standardization Explosion Java is an attempt to standardize everything –language features –interface libs guis dbs communication application development Microsoft is doing the same thing in its own way Is this an oxymoron? Possibly. Each have an explosion of standardization. There are always competing standardization and degrees.

So what now? You’re jumping in midstream so it’s hard to see. Technologies have a way of overwhelming Technologies have a way of emerging to the masses (programmers) if they succeed. J2EE is a standardization of application development. It’s not simple… but not too hard for you!

J2SE and J2EE Basic libraries for java development I/o GUIs applets etc Based on J2SE Can UTILIZE EJB Uses other technologies Defines a Specification Components are constrained to abide by interface specs if they play J2EE

From Roman

Business Logic BackEnd Client Interface From Roman Our Main Focus

J2EE Technologies EJB RMI JNDI JDBC JTS (Transactions) servlets JSP JAAS (Authorization & Authentification)