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Introducing the Java and Oracle Platforms

Introducing the Java and Oracle Platforms. Objectives. After completing this lesson, you should be able to do the following: Identify the key elements of Java Describe the Java Virtual Machine (JVM) Examine how Java is used to build applications

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Introducing the Java and Oracle Platforms

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  1. Introducing the Javaand Oracle Platforms

  2. Objectives • After completing this lesson, you should be able to do the following: • Identify the key elements of Java • Describe the Java Virtual Machine (JVM) • Examine how Java is used to build applications • Identify the key components of the J2SE Java Development Kit (known as JDK or SDK) • Describe Java deployment options

  3. What Is Java? • Java: • Is a platform and an object-oriented language • Was originally designed by Sun Microsystems for consumer electronics • Contains a class library • Uses a virtual machine for program execution

  4. Key Benefits of Java • Object-oriented • Interpreted and platform-independent • Dynamic and distributed • Multithreaded • Robust and secure

  5. An Object-Oriented Approach • Objects and classes • An object is a run-time representation of a “thing.” • A class is a “static definition of things.” • Class models elaborate: • Existing classes and objects • Behavior, purpose, and structure • Relationships between classes • Relationships between run-time objects • Same models exist throughout the project. Analysis Design Implementation Integrationand testing CLASS MODELS

  6. Platform Independence • Java source code is stored as text in a .java file. • The .java file is compiled into .class files. • A .class file contains Java bytecodes (instructions). • The bytecodes are interpreted at run time. • The Java .class file is the executable code. Compile JVM (javac) (java) Running program Movie.java Movie.class

  7. Using Java with EnterpriseInternet Computing Web server Application server Client Data Presentation Businesslogic • Servlets • JavaServer Pages (JSPs) • Enterprise JavaBeans (EJB) • CORBA

  8. Using the Java Virtual Machine Operating system JVM Application

  9. How Does JVM Work? • The class loader loads all required classes. • JVM uses a CLASSPATH setting to locate class files. • JVM Verifier checks for illegal bytecodes. • JVM Verifier executes bytecodes. • JVM may invoke a Just-In-Time (JIT) compiler. • Memory Manager releases memory used by the dereferenced object back to the OS. • JVM handles Garbage collection.

  10. Benefits of Just-In-Time (JIT) Compilers • JIT compilers: • Improve performance • Are useful if the same bytecodes are executed repeatedly • Translate bytecodes to native instruction • Optimize repetitive code, such as loops • Use Java HotSpot VM for better performance and reliability

  11. Implementing Securityin the Java Environment Language and compiler Class loader Bytecode verifier Interface-specific access

  12. Deployment of Java Applications • Client-side deployment: • JVM runs stand-alone applications from the command line. • Classes load from a local disk, eliminating the need to load classes over a network. • Server-side deployment: • Serves multiple clients from a single source • Is compatible with a multitier model for Internet computing.

  13. Using Java with Oracle 10g Web server Application server Client Data Presentation Businesslogic Oracledatabase OracleApplication Server

  14. Java Software Development Kit • Sun Java J2SE (known as JDK and Java SDK) provides: • Compiler (javac) • Core class library • classes.zip • rt.jar • Debugger (jdb) • Bytecode interpreter: The JVM (java) • Documentation generator (javadoc) • Java Archive utility (jar) • Others J2SE

  15. Using the Appropriate Development Kit • Java2 comes in three sizes: • J2ME (Micro Edition): Version specifically targeted at the consumer space • J2SE (Standard Edition): Complete ground-up development environment for the Internet • J2EE (Enterprise Edition): Everything in the J2SE plus an application server and prototyping tools

  16. Integrated Development Environment Development Debug UML Exchange ADF Database Synchronized changes XML HTML SCM Deployment

  17. Exploring the JDeveloper Environment Component Palette System Navigator Code Editor Property Inspector

  18. Oracle10g Products

  19. Summary • In this lesson, you should have learned the following: • Java code is compiled into platform-independent bytecodes. • Bytecodes are interpreted by JVM. • Java applications can be stand-alone or implemented across an Internet-computing model.

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