Java5 Annotations

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Java5 Annotations

• Aino Andriessen

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Inleiding

• Java5
• annotations (jsr 175)
• generics
• enhanced for loop
• auto(un)boxing
• enumerations
• static imports
• variable arguments
• formatted output
• enhanced java.util.Properties
• jvm enhancements
• JMX console

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Java 5

• Ondersteuning ides
• JDeveloper 10.1.3 preview
• tools gt Manage Libraries gt toevoegen java5
• project properties gt libraries
• Eclipse 3.1
• NetBeans
• IDEA
• ...

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Wat zijn annotaties?

• The metadata feature in J2SE 5.0 provides the
  ability to associate additional data alongside
  Java types, methods, and fields. This additional
  data, or annotation, can be read by the javac
  compiler or other tools, and depending on
  configuration can also be stored in the class
  file and can be discovered at runtime using the
  Java reflection API.
• Extra informatie in de java klasse tbv code
  generatie, run-time informatie

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Metadata / Annotaties

• Program annotation facility
• we already have _at_deprecated, transient
• Can add annotions to any declaration, including
  package
• Annotations are instances of annotation types
  which can be declared.
• Annotations can be processed by tools, or by
  reflective code.
• code generation, class loading, runtime
• Some annotion types built in

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• Niet nieuw
• JavaDoc
• XDoclet
• (Apache/Bea) Beehive
• .NET 2.0

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Annotatie typen

• Marker annotation
• _at_Financial public class Invoice ...
• Normal annotation name/value pairs
• _at_optimise( levelhigh threadsafefalse
  lastCheck2/12/2004)
• public void credit(Money amount) ...

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Built-ins - Override

• java.lang.Override
• target method
• marks methods intended to override a superclass
  method
• kan een compiler error opleveren

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Buit-ins - Documented

• java.lang.annotation.Documented
• documentatie van de annotatie door bijv. JavaDoc

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Buit-ins - Deprecated

• java.lang.annotation.Deprecated
• target class, method, field

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Buit-ins - Inherited

• java.lang.annotation.Inherited
• Indicates that an annotation type is
  automatically inherited.
• _at_inherited
• public _at_interface Author ...
• _at_Author(fred)
• public class MySuperclass ..
• public class MySubclass extends MySuperclass
  ... // will inherit the Author annotation

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Built-ins - Retention

• java.lang.annotation.Retention
• Defines the availability (enum java.lang.annotatio
  n.RetentionPolicy)
• source
• class (default)
• runtime

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Built-ins - Target

• java.lang.annotation.Target
• Indicate the type of program element (enum
  java.lang.annotation.ElementType) to which the
  declared annotation is applicable
• TYPE
• FIELD
• METHOD
• PARAMETER
• CONSTRUCTOR
• LOCAL_VARIABLE
• ANNOTATION_TYPE
• PACKAGE
• default all

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Built-ins - SuppressWarnings

• java.lang.SuppressWarnings
• Indicatie dat de compiler warnings onderdrukt
  moeten worden.

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User-defined

• demo

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Toepassingen

• JEE 5
• EJB 3.0
• JUnit 4
• ...

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Session bean

• package oracle.ejb30
• import javax.ejb.Remote
• _at_Remote
• public interface HelloWorld
• public void sayHello(String name)
• -----------
• package oracle.ejb30
• import javax.ejb.Stateless
• _at_Stateless
• public class HelloWorldBean implements HelloWorld
  
• public void sayHello(String name)
• System.out.println("Hello "name " from
  first EJB3.0")

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session bean - 2

• Context context new InitialContext()
• HelloWorld helloWorld (HelloWorld)context.lookup
  ("javacomp/env/ejb/HelloWorld")
• helloWorld.sayHello(args0 )

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Entity bean

• _at_Entity
• _at_Table(name "EMP")
• public class Employee implements
  java.io.Serializable
• private int empNo
• private String eName
• private double sal
• _at_Id
• _at_Column(name"EMPNO", primaryKeytrue)
• public int getEmpNo()
• return empNo
• ..

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entity bean - 2

• _at_Stateless
• public class EmployeeFacadeBean implements
  EmployeeFacade
• _at_Resource
• private EntityManager em
• private Employee emp
• public Employee findEmployeeByEmpNo(int empNo)
• return ((Employee) em.find("Employee",empNo))
  
• public void addEmployee(int empNo, String
  eName, double sal)
• if (emp null) emp new Employee()
• ...
• em.persist(emp)

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Apt

• Annotation Processing Tool

src
class
apt
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XDoclet

• Code generation based on javadoc comments
• Original for EJB

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Referenties

• Java5
• http//java.sun.com/developer/technicalArticles/re
  leases/j2se15langfeat/
• http//java.sun.com/reference/tigeradoption/
• Annotations
• http//java.sun.com/j2se/1.5.0/docs/guide/language
  /annotations.html
• http//www.javaworld.com/javaworld/jw-07-2004/jw-0
  719-tiger3.html
• http//www.onjava.com/pub/a/onjava/2004/04/21/decl
  arative.html
• http//www-128.ibm.com/developerworks/java/library
  /j-cwt08025.html
• EJB 3.0
• http//www.oracle.com/technology/tech/java/ejb30.h
  tml
• Apt
• http//java.sun.com/j2se/1.5.0/docs/guide/apt/Gett
  ingStarted.html