Java and Java platforms
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This set of slides introduces the basic concepts of Java development. First, the difference between Java as the programming language and Java as a platform is stated. Then, the different Java platforms are presented, with a particular interest in Java Standard Edition and Java Enterprise Edition. With respect to the latter, the roles and differences between the many JEE containers are discussed.
![The Java programming language
The Java programming language is a high-level, object-oriented
programming language firstly released in 1995
class App {
public static void main(String[] args) {
System.out.println("Hello World!");
}
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Java and Java platforms
- 1. Java & Java pla(orms Ilio Catallo - [email protected]
- 2. Outline • Java technology • JEE applica2ons • References
- 4. Java technology Java is both a programming language and a pla-orm
- 5. The Java programming language The Java programming language is a high-level, object-oriented programming language firstly released in 1995 class App { public static void main(String[] args) { System.out.println("Hello World!"); } }
- 6. Pla$orms A pla$orm is the hardware and so.ware environment in which a program runs
- 7. Java pla'orms A Java pla'orm is a par(cular environment in which Java applica(ons run
- 8. Pla$orms Pla$orms usually consist of a combina2on of the opera&ng system and the underlying hardware
- 9. Pla$orms Example: Microso) Windows on Intel architecture
- 10. Java pla'orm The Java pla*orm is a so#ware-only pla*orm that runs on top of other pla*orms ┌───────────────────────────────────┐ │ Java program │ ├───────────────────────────────────┤ │ Java platform │ ├───────────────────────────────────┤ │ Host platform │ └───────────────────────────────────┘
- 11. Java pla'orm Every Java pla+orm consists of: • A Java Virtual Machine (JVM) • A set of applica8on programming interfaces (APIs)
- 12. Java virtual machine The Java Virtual Machine (JVM) is an abstract computer that runs compiled Java programs ┌───────────────────────────────────┐ │ Java program │ ├─────────┬─────────────────────────┤ │ API │ │ ├─────────┘ Java VM │ │ │ ├───────────────────────────────────┤ │ Host platform │ └───────────────────────────────────┘
- 13. Java virtual machine The JVM is virtual because it is implemented in so7ware on top of a real host pla:orm ┌───────────────────────────────────┐ │ Java program │ ├─────────┬─────────────────────────┤ │ API │ │ ├─────────┘ Java VM │ │ │ ├───────────────────────────────────┤ │ Host platform │ └───────────────────────────────────┘
- 14. Java virtual machine Java programs are compiled into Java bytecode
- 15. Java virtual machine Java bytecode is the machine language of the JVM
- 16. Java API The Java API is a large collec2on of ready-made so9ware components
- 17. Java API It is grouped into libraries (packages) of related classes and interfaces
- 18. Java API For instance, the Collec0on API (java.util) provides the most commonly used data structures
- 19. Java pla'orm specifica0ons There exist three Java pla/orm specifica4ons • Java Standard Edi-on • Java Enterprise Edi-on • Java Micro Edi-on
- 20. Java pla'orm specifica0ons There exist three Java pla/orm specifica4ons • Java Standard Edi,on • Java Enterprise Edi,on • Java Micro Edi-on
- 21. Java Standard Edi,on Java Standard Edi,on (JSE) is a pla,orm specifica3on for developing desktop applica,ons
- 22. Java Standard Edi,on Java Standard Edi,on is the founda,on for developing in the Java language, as it contains the set of Java standard libraries
- 23. Java Standard Edi,on Java Standard Edi,on is just a specifica(on, not an implementa,on
- 24. Java Standard Edi,on Vendors and open source projects are free to provide their own implementa6on • Oracle JDK • OpenJDK
- 25. Java Enterprise Edi.on Java Enterprise Edi.on (JEE) provides APIs and the run6me environment for developing enterprise applica.ons
- 26. Java Enterprise Edi.on Typical features of an enterprise applica1on • Large-scale • Distributed • Highly-available
- 27. Java Enterprise Edi.on Java Enterprise Edi.on is a superset of Java Standard Edi.on
- 28. Java Enterprise Edi.on Therefore, JSE APIs can be used in any JEE applica:on
- 29. Java Enterprise Edi.on JEE extends the JSE pla/orm with addi$onal APIs: • Java Servlet API (javax.servlet) • JavaServer Pages API (javax.servlet) • Java Persistence API (java.persistence) • Enterprise JavaBeans API (javax.ejb)
- 30. JEE specifica+on Java Enterprise Edi.on is just a specifica(on, not an implementa.on
- 31. JEE specifica+on Namely, JEE is an umbrella specifica.on that references a number of other more detailed specifica9on ┌──────────────────────────────────────────────┐ │ ┌──────────────┐ │ │ │ EJB │ │ │ ┌─────────────┐ │Specification │ │ │ │ Servlet │ └──────────────┘ │ │ │Specification│ │ │ └─────────────┘ ┌─────────────┐ │ │ │ JPA │ │ │ ┌─────────────┐ │Specification│ │ │ │ JSP │ └─────────────┘ │ │ │Specification│ │ │ └─────────────┘ │ └──────────────────────────────────────────────┘ JEE specification
- 32. JEE implementa,ons Vendors and open source projects are free to implement one or more JEE APIs ┌──────────────────────────────────────────────┐ │ ┌──────────────┐ │ │ │ EJB │ │ │ ┌─────────────┐ │Specification │ │ │ │ Servlet │ └──────────────┘ │ │ │Specification│ │ │ └─────────────┘ ┌─────────────┐ │ │ │ JPA │ │ │ ┌─────────────┐ │Specification│ │ │ │ JSP │ └─────────────┘ │ │ │Specification│ │ │ └─────────────┘ │ └──────────────────────────────────────────────┘ JEE specification
- 33. JEE implementa,ons "Apache Tomcat 8.0 implements the Servlet 3.1 and JavaServer Pages 2.3 specifica?ons" (Apache Tomcat 8.0 documenta3on)
- 34. JEE implementa,ons "In addi(on to its own "na(ve" API, Hibernate is also an implementa(on of the Java Persistence API (JPA) specifica(on" (Hibernate ORM)
- 35. JEE Applica*ons
- 36. JEE Components Java EE applica*ons are made up of components
- 37. JEE Components A JEE component is a self-contained so/ware unit
- 38. JEE Components You may already know a par0cular JEE component: servlets public class MyServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response); public void doPost(HttpServletRequest request, HttpServletResponse response); public void init(); public void destroy(); }
- 39. JEE Components There exist different types of JEE components • Web components • Business components • Applica3on client components
- 40. JEE Components Web components: • Servlets • JavaServer Pages (JSP) and JavaServer Faces (JSF)
- 41. JEE Components Business components: • Enterprise JavaBeans
- 42. JEE Components Applica'on client components: • Applets • Applica+on Clients
- 43. JEE Containers JEE components live within a container. A container is the JEE run6me environment
- 44. JEE Containers A container provides certain services to the components it hosts, such as: • Life-cycle management • Dependency injec4on • Concurrency
- 45. JEE Containers Different kinds of components live in different kinds of containers
- 46. JEE servers A Java EE server (also called applica&on server) implements the en6re set of JEE APIs and provides the standard JEE containers
- 47. JEE servers The reference JEE server is Oracle Glassfish. Possible alterna8ve implementa8ons: • IBM WebSphere • Apache TomEE • Red Hat JBoss
- 48. JEE servers JEE server ┌────────────────────────────────────────────────────┐ │ Web container EJB container │ │ ┌──────────────────────┐ ┌─────────────────────┐ │ │ │ ┌─────────────┐ │ │ ┌─────────────┐ │ │ │ │ │ Servlet A │ │ │ │ EJB D │ │ │ │ │ └─────────────┘ │ │ └─────────────┘ │ │ ┌──────┐ ┌─────────┐ │ │ ┌──────────┐│ │ ┌──────────┐│ │ │ │ │ Browser ├───┼─┤ │ JSP C │├───┤ │ EJB E │├─┼───┤ DB │ └─────────┘ │ │ └──────────┘│ │ └──────────┘│ │ │ │ │ │┌─────────────┐ │ │┌─────────────┐ │ │ └──────┘ │ ││ Servlet B │ │ ││ EJB F │ │ │ │ │└─────────────┘ │ │└─────────────┘ │ │ │ └──────────────────────┘ └─────────────────────┘ │ └────────────────────────────────────────────────────┘
- 49. Business logic At the heart of any applica0on lies its business logic
- 50. "We call business logic any program code that pertains to the purpose of a so6ware applica8on"
- 51. Business logic In a chess game, the business logic handles: • The board and pieces • Their movements • The rules of the game
- 52. Business logic Such concerns are independent of, e.g., how pieces will be displayed
- 53. Business logic Such concerns are independent of, e.g., how pieces will be displayed
- 54. The role of EJBs In a JEE applica+on, EJBs encapsulate the business logic @Stateless public class FlightServiceBean { List<SpecialDeal> getSpecialDeals() { ... } List<Flight> findFlights(String queryString) { ... } }
- 55. The role of EJBs Moreover, the EJB container provides fundamental services such as security and transac+ons @Stateless @TransactionManagement(TransactionManagementType.CONTAINER) public class FlightServiceBean { List<SpecialDeal> getSpecialDeals() { ... } List<Flight> findFlights(String queryString) { ... } }
- 56. The role of EJBs Thanks to this, developers are free to focus of defining and implemen6ng the business logic
- 57. JEE stack However, many vendors and open source projects implement only a subset of the JEE specifica;on
- 58. JEE stack For instance, Apache Tomcat provides only a Web container
- 59. Web container Web server ┌──────────────────────────┐ │ │ │ Web container │ │ ┌──────────────────────┐ │ │ │ ┌─────────────┐ │ │ │ │ │ Servlet A │ │ │ │ │ └─────────────┘ │ │ ┌──────┐ ┌─────────┐ │ │ ┌──────────┐│ │ │ │ │ Browser ├───┼─┤ │ JSP C │├─┼───┤ DB │ └─────────┘ │ │ └──────────┘│ │ │ │ │ │┌─────────────┐ │ │ └──────┘ │ ││ Servlet B │ │ │ │ │└─────────────┘ │ │ │ └──────────────────────┘ │ │ │ └──────────────────────────┘
- 60. Can we built enterprise applica0ons without the whole JEE stack?
- 61. Can we write enterprise applica.on without the need of an applica.on server?
- 62. The Spring Framework The solu)on comes in the form of the Spring framework
- 63. The Spring Framework …but this is something we will inves1gate in the next lecture ;-)
- 64. References
- 65. References • Antonio Goncalves, Beginning Java EE 7, Apress Publica:ons • Chris Richardson, POJOs in Ac:on, Manning Publica:ons • D, Panda, R. Rahman, D. Lane, EJB3 In Ac:on, Manning Publica:ons • Oracle, GeGng Started
- 66. References • Bill Venners, The lean, mean, virtual machine • Oracle, Java EE 7 Tutorial • Wikipedia, Java EE