EBIZ 5535 Lecture 11

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EBIZ 5535Lecture 11

• A Simple J2EE Application

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A Slight Tangent

• For the final project, we will use a simplified
  WAF. To understand how to use this, lets look at
  a couple of very simple applications that use
  J2EE
• One is used in lab 6

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StockQuote Application

• Has a java client and a web interface (a jsp) to
  a Session Bean that is a stock quoting stub
• Doesnt actually look the current quotes up, just
  has quotes stored in a local table
• J2EE application consists of
• A client call with stock symbol on command
  line, gives quote
• A jsp gives a list of stock symbols to choose
  from, gets quote
• A session bean that looks up the symbol and
  returns the quote

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Directory Structure
Build application
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The StockQuoteBean

• Very Simple
• Given a stock symbol, look it up in internal
  table, if found return quote
• This is an example of business logic
• Used by two different user interfaces
• A client application
• A web page
• These give different ways of accessing stock
  information

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StockQuoteBean

• public class StockQuoteBean implements
  SessionBean
• private HashMap _quotes
• public StockQuoteBean ()
• _quotes new HashMap ()
• _quotes.put ("AMD", new Double (6.91))
• _quotes.put ("DELL", new Double (28.30))
• _quotes.put ("GTW", new Double (2.98))
• _quotes.put ("HPQ", new Double (20.48))
• _quotes.put ("IBM", new Double (87))
• _quotes.put ("INTC", new Double (17.06))
• _quotes.put ("MSFT", new Double (55.81))
• _quotes.put ("ORCL", new Double (13.01))
• _quotes.put ("SUNW", new Double (3.76))

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• public double getQuote (String stock) throws
  InvalidStockException
• Double value (Double) _quotes.get
  (stock.toUpperCase())
• if (value null)
• throw new InvalidStockException ("No data
  for symbol " stock)
• return value.doubleValue ()
• public Collection getStocks() return
  _quotes.keySet()
• public void ejbCreate ()
• public void ejbRemove ()
• public void ejbActivate ()
• public void ejbPassivate ()
• public void setSessionContext (SessionContext sc)
  

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Home Interface

• public interface StockQuoteHome
• extends javax.ejb.EJBHome
• public static final String COMP_NAME"javacomp
  /env/ejb/ex2/StockQuote"
• public static final String JNDI_NAME"ejb/ex2/S
  tockQuote"
• public edu.uwyo.StockQuote create() throws
  javax.ejb.CreateException, java.rmi.RemoteExceptio
  n

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Remote Interface

• public interface StockQuote extends
  javax.ejb.EJBObject
• public double getQuote( java.lang.String stock )
  throws edu.uwyo.InvalidStockException,
  java.rmi.RemoteException
• public Collection getStocks() throws
  java.rmi.RemoteException

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The Web Interface

• String errmsg ""
• double quoteValue -1
• Iterator symbolIter null
• String quoteSymbol request.getParameter
  ("quoteSymbol")
• try
• Context initial new InitialContext ()
• StockQuoteHome home (StockQuoteHome)
  initial.lookup("ejb/ex2/StockQuote")
• StockQuote quote home.create ()
• if (quoteSymbol ! null) quoteValue
  quote.getQuote (quoteSymbol)
• symbolIter quote.getStocks().iterator(
  )
• quote.remove ()
• catch (InvalidStockException e)
• errmsg "Invalid Stock Symbol "
  quoteSymbol

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• Stock Quote Web Client
• Stock Quote Web Client
• Stock Symbol
• while (symbolIter.hasNext
  ())
• symbolIter.next()
• quoteSymbol.toUpperCase().equals(symbol))
• "
  
• "ption

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• Current Quote
• Double.toString(quoteValue) )
• type"submit"

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The Client

• public class StockQuoteClient
• public static void main (String args)
• try
• Context initial new InitialContext ()
• StockQuoteHome home (StockQuoteHome)
  initial.lookup("ejb/ex1/StockQuote")
• StockQuote quote home.create ()
• for (int i0 i
• try
• double value quote.getQuote (argsi)
• System.out.println (argsi " "
  value)
• catch (InvalidStockException e)
• System.out.println (argsi " Not
  Found")
• quote.remove ()
• catch (Exception e)

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Building the Application

• All the files in the application are jarred for
  distribution
• There is one jar file for each tier
• These jar files can be jarred again into a .ear
  file
• The files contain
• The client, the beans, the interfaces, and
  application specific exceptions
• Xml files describing the application

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Organization of The Distribution
optional
Enterprise Application
ejb tier
web tier
Client Tier
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Bean Descriptor File ejb-jar.xml

• No Description.
• StockQuoteBean class is an
  enterprise java bean that finds the current stock
  price of a given stock.
• Returns the current value
  of a stock
• ex2/StockQuote
• edu.uwyo.StockQuoteHome
• edu.uwyo.StockQuote
• edu.uwyo.StockQuoteBeanlass
• Stateless
• Containertype

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Additional Bean Descriptor jboss.xml

• ex2/StockQuote
• ejb/ex2/StockQuote
  
• ex2/StockInfo
• ejb/ex2/StockInfo

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Client Descriptor jboss-web.xml

• ejb/ex2/StockQuote
• ejb/ex2/StockQuote

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Web Description web-client.xml

• Stock Quote Web
  Client
• index.jsp
• index.html
• ejb/ex1/StockQuoteme
• Session
• edu.uwyo.StockQuoteHome
• edu.uwyo.StockQuote

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Organization of files
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Building the Application Distribution

• Use ant
• To compile java files
• Package class and xml files into jar, war, and
  ear files
• build.xml file controls the build process
• References customize.properties file

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customize.properties

• jboss.home/home/faculty/ruben/jboss-3.0.4
• jboss.configurationdefault
• xdoclet.home/usr/local/xdoclet-1.1.2
• xdoclet.forcefalse
• ejb.version2.0
• jboss.version3.0
• type.mappingHypersonic SQL
• datasource.namejava/DefaultDS
• servlet-lib.path/home/faculty/jvb/jboss-3.0.4/ser
  ver/default/lib/javax.servlet.jar

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Extending the StockQuote Application to Use a
Database

• Introduce a Data Access Object (DAO)
• This is a class that accesses a database through
  JDBC
• Then in the StockQuoteBean, we call methods of
  the DAO to access the Database