Java and Java platforms
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The document outlines Java technology, including its definition as a high-level programming language and its platform environment. It delves into the Java Virtual Machine (JVM), various Java platform specifications such as Java Standard Edition (JSE) and Java Enterprise Edition (JEE), and the components of JEE applications, which consist of different types of software components and the containers that host them. Additionally, it discusses the business logic encapsulated by Enterprise JavaBeans (EJBs) and introduces the Spring framework as an alternative for enterprise application development.
![The Java programming language
The Java programming language is a high-level, object-oriented
programming language firstly released in 1995
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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 - info@iliocatallo.it
- 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