Java Technologies Overview

1
Java Technologies Overview

• Chris Bowlds
• Senior Oracle Consultant
• chris.bowlds_at_casetech.net
• www.casetech.net
• www.chrisbowlds.com

2
Goals

• Introduce the three major Java Editions
• Describe the major technologies for the first two
• No detailed wireless coverage
• Outline the Oracle products that implement these
  technologies

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J2SE, J2EE, J2ME

• Java 2 Standard Edition (J2SE)
• Used to write standalone Java Applications and
  Applets
• Java 2 Enterprise Edition (J2EE)
• A set of APIs and server specifications built on
  top of J2SE for building web applications.
• Java 2 Micro Edition (J2ME)
• A pared down version of J2SE and APIs for
  wireless and embedded device programming.

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J2SE

• Not just a language a platform
• Key terms
• JVM Java Virtual Machine
• A virtual (imaginary) machine that binary code is
  compiled to, rather than platform dependent
  binary formats.
• .java files -gt .class files -gt run by the Java
  interpreter
• JRE Java Runtime Environment
• The runtime implementation of the JVM.
• All you need to run Java programs and Applets.
• SDK Software Development Kit
• Needed to develop Java programs
• Includes the JRE to run Java
• Bundled with JDeveloper (if you download the big
  one)
• Used to be called Java Development (JDK)

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J2SE

• http//java.sun.com/j2se/1.4.2/docs/index.html

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Select Component Descriptions

• Java Runtime Typically java.exe or jre.exe
• What actually runs interprets .class files.
• Part of the JRE.
• Java Plug-in
• Allows running Java Applets in a web browser.
• Java Web Start
• Application deployment technology supporting
  automatic updates and secure runtime environment.

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API's you're likely to need as an Oracle developer

• java.lang
• Standard classes such as Object, System, Integer,
  and String
• java.util
• Collections, Date, Math, StringTokenizer, etc.
• javax.xml
• Java API for XML Processing (JAXP)
• Document Object Model (DOM), Simple API for XML
  Processing (SAX), and Extensible Stylesheet
  Transformation (XSL) support.
• java.sql
• JDBC - database access
• javax.swing
• Graphical User Interface (GUI) toolkit. Write
  custom Forms widgets.

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J2EE

• Built on J2SE - does NOT stand alone!
• A set of specifications for writing components
  that will run in standard J2EE servers.
• (Supposedly) brings the portability of Java to
  web development.

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J2EE - Three Primary Technologies

• Servlets
• Server side Java code.
• Similar to PL/SQL web code, but written in Java.
• Java code that has print statements to generate a
  web page.
• JSP's
• JavaServer Pages
• Server side Java code.
• The inverse of a Servlet HTML code with Java
  code embedded.
• EJB's
• Enterprise JavaBeans
• Java components that encapsulate business logic
  to be shared across the enterprise.

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Typical N-Tier Architecture
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Containers, Components

• A standard design pattern in J2EE is the use of
  Containers and Components.
• Containers
• Specified by Sun
• Implemented by Application Server vendors.
• Handle the plumbing code so that application
  programmers can focus on business logic.
• Components
• Written by application programmers to run inside
  of Containers.
• Focus on business logic.

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Examples of Containers and Components

• Servlets and JSPs
• The Servlet Container (Tomcat, 9iAS, etc.)
  handles plumbing code such as TCP/IP network
  traffic using the HTTP protocol, using cookies to
  store session data.
• The Servlet Components (written by developers)
  use APIs to interact with the Container. Code
  focuses on business logic.
• EJBs
• The EJB Container (9iAS, JBoss, etc.) handles
  plumbing code such as distributed communication,
  threading, scaling, transaction management, and
  even persistence.
• The EJBs (written by developers) use APIs to
  interact with the Container. Code focuses on
  business logic.

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Other Prominent J2EE Technologies

• JNDI
• Java Naming and Directory Interface
• A standard API for talking to directories, such
  as EJB servers and LDAP directories.
• JMS
• Java Messaging Service, for asynchronous
  interactions.
• This is getting increasingly important for
  scalability.
• Java Mail
• Web Services support
• JAR, WAR, EAR files
• Theyre all in .zip format.
• Java, Web, and Enterprise Archives, respectively.
• Standard file formats used for deploying Java
  applications.

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Java in Oracle

• Client Tier
• Forms 9i client runs as an Applet
• Behavior of Applet is based on .FMX files
• Can have custom Java Beans embedded
• Middle Tier
• Forms 9i server
• Custom Java code can be imported and run on the
  Forms server.
• 9i Application Server (9iAS)
• Oracle Objects For J2EE (OC4J) is Oracle's J2EE
  server implementation
• Servlets, JSPs, EJBs, JMS, etc.

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Java in Oracle

• Database Tier
• Capability of running J2EE code, but DON'T.
• This has been replaced by 9iAS.
• Java Stored Procedures
• Works great on small things.
• Have encountered problems when there are a lot of
  dependencies on third party code on an upgraded
  database.
• Probably completely safe on a freshly installed
  database.

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Contact Information
Chris Bowlds chris.bowlds_at_casetech.net www.chrisb
owlds.com
202 543 4499
GSA IT Schedule GS-35F-0605M
www.casetech.net