Presentación de PowerPoint

Persistencia
Grupo de Construcción de Sw
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Referencias
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http://www.objectdb.com/api/java/jpa
http://www.javaworld.com/article/2077817/jav
a-se/understanding-jpa-part-1-the-objectoriented-paradigm-of-datapersistence.html?page=2
http://blog.jbaysolutions.com/2011/09/10/jpa_
getting_started_part1/
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Conceptos claves
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JDBC
Object-relational impedance mismatch
(desajuste entre el modelo objeto y el
relacional)
ORM
JPA
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JDBC
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Java Database Connectivity
Conectarse y acceder una base de datos
relacional (crear tablas, actualizar, borrar,
…)
Utilizando SQL
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JDBC
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http://www.tutorialspoint.com/jdbc/jdbcsample-code.htm
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//STEP 1. Import required packages
import java.sql.*;
public class FirstExample {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/EMP";
// Database credentials
static final String USER = "username";
static final String PASS = "password";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try{
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
//STEP 3: Open a connection
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL,USER,PASS);
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//STEP 4: Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
String sql;
sql = "SELECT id, first, last, age FROM Employees";
ResultSet rs = stmt.executeQuery(sql);
//STEP 5: Extract data from result set
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
//STEP 6: Clean-up environment
rs.close();
stmt.close();
conn.close();
…
…
}//end main
}//end FirstExample
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Object-relational impedance mismatch
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(desajuste entre el modelo objeto y el
relacional)
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Granularidad
Navegación
Herencia
Tipos de datos
Asociaciones
Identidad
Igualdad
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Conceptos claves: ORM
Object Relational Mapping
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Conceptos claves: ORM
Object Relational Mapping
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Conceptos claves: ORM
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JPA
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Es un estándar de un ORM
Es una especificación
Varias implementaciones:
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Hibernate, topLink, eclipseLink, JDO, …
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JPA Java Persistence API
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Mapea los objetos a tablas en la base de
datos y se ocupa de su sincronización
…
Customer customer = new Customer();
customer.setFirstName("Charles");
customer.setLastName("Dickens");
customer.setCustType("RETAIL");
customer.setStreet("10 Downing
Street");
customer.setAppt("1");
customer.setCity("NewYork");
customer.setZipCode("12345");
em.persist(customer);
…
Cuando se cambian los
valores en los objetos
(customer) se actualiza a la
base de datos a través de un
manejador de persistencia
(em)
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JPA Java Persistence API

Mapea los objetos a tablas en la base de
datos
…
Customer customer = new Customer();
customer.setFirstName("Charles");
customer.setLastName("Dickens");
customer.setCustType("RETAIL");
customer.setStreet("10 Downing
Street");
customer.setAppt("1");
customer.setCity("NewYork");
customer.setZipCode("12345");
1. Qué tipo de clase es
Customer ?
2. Qué tipo de objeto es em y
qué relación tiene con la base
de datos?
em.persist(customer);
…
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import javax.persistence.*;
import java.io.Serializable;
import java.util.Date;
@Entity
public class Customer {
@Id
@GeneratedValue(generator = “Customer")
private long custId;
private String firstName;
private String lastName;
private String street;
private String appt;
private String city;
private String zipCode;
private String custType;
private Date updatedTime;
Un Entity es un POJO anotado
POJO (Plain Old Java Object)
// Getters and setters go here
......................
}
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@Default
@Stateless
@LocalBean
public class SportLogic implements ISportLogic {
@PersistenceContext(unitName = "SportClassPU")
protected EntityManager entityManager;
public SportDTO createSport(SportDTO sport) {
SportEntity entity = SportConverter.persistenceDTO2Entity(sport);
entityManager.persist(entity);
return SportConverter.entity2PersistenceDTO(entity);
}
public List<SportDTO> getSports() {
Query q = entityManager.createQuery("select u from SportEntity u");
return SportConverter.entity2PersistenceDTOList(q.getResultList());
}
public SportPageDTO getSports(Integer page, Integer maxRecords) {
..
}
public SportDTO getSport(Long id) {
…
}
public void deleteSport(Long id) {
SportEntity entity = entityManager.find(SportEntity.class, id);
entityManager.remove(entity);
}
public void updateSport(SportDTO sport) {
…
}
}
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@Default
@Stateless
@LocalBean
public class SportLogic implements ISportLogic {
@PersistenceContext(unitName = "SportClassPU")
protected EntityManager entityManager;
Se inyecta un EntityManager de
acuerdo con la info definida en
persistence.xml
public SportDTO createSport(SportDTO sport) {
SportEntity entity = SportConverter.persistenceDTO2Entity(sport);
entityManager.persist(entity);
return SportConverter.entity2PersistenceDTO(entity);
}
public List<SportDTO> getSports() {
Query q = entityManager.createQuery("select u from SportEntity u");
return SportConverter.entity2PersistenceDTOList(q.getResultList());
}
public SportPageDTO getSports(Integer page, Integer maxRecords) {
..
}
public SportDTO getSport(Long id) {
…
}
public void deleteSport(Long id) {
SportEntity entity = entityManager.find(SportEntity.class, id);
entityManager.remove(entity);
}
public void updateSport(SportDTO sport) {
…
}
}
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JPQL
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http://www.objectdb.com/java/jpa/query
http://docs.oracle.com/cd/E11035_01/kodo41
/full/html/ejb3_overview_query.html
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