Java Persistance API (JPA)
javax.persistence package
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The Java Persistence API deals with the way relational data is mapped to Java objects ("persistent entities"), the way that these objects are stored in a atabase so that they can be accessed at a later time, and the continued existence of an entity's state even after the application that uses it ends.
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Java Persistence API standardizes object-relational mapping.
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Provides Object-oreinted interface to data (even if underlying database is not an object store)
Google App Engine Note:
Supported for use in Google App Engine to access the Google App Engine Datastore (object database)
A lightweight Java Class whose state is tied either to
- a row (data base entry) in a relational database table
- an object entry in a object database (GAE Entity)
import java.util.Dateimport java.util.Date; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; @Entity public class Book { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id;
private String title; private String author; private int copyrightYear; private Date authorBirthdate;
public Long getId() { return id; }
public String getTitle() { return title; }
public void setTitle(String title) { this.title = title; }
public String getAuthor() { return author; }
public void setAuthor(String author) { this.author = author; }
public int getCopyrightYear() { return copyrightYear; }
public void setCopyrightYear(int copyrightYear) { this.copyrightYear = copyrightYear; }
public Date getAuthorBirthdate() { return authorBirthdate; }
public void setAuthorBirthdate(Date authorBirthdate) { this.authorBirthdate = authorBirthdate; } }
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