guzra huwa jamana ata nahi dubara

hafez khuda tumhara

khushiya thi chaar din ki

aason hai umr bhar ke

tanhahiyon me aksar royenge yaad karke

wo waqt ke jo hum ne ek saath hai guzaara

meri khasam hai mujko tum bewafa na kehna

majboor thi mahabot sabh kuch pada hai sehna

tuta hai zindegi ka ab aakhri sahara

mere liye sahr bhi aayi hai raath bankar

nikla mera janaza meri barath ban kar

accha huwa jo tumne dekha na ye nazara

guzra huwa jamana ata nahi dubara

hafez khuda tumhara

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Access multiple Databases in JPA

According to JPA specification we can define multiple "persistence-unit" elements (i.e. like below) in persistence.xml file and can easily refer them inside Dao layers as this. public class PolarDaoImpl { @PersistenceContext(unitName="PolarPU") protected EntityManager entityManager; -- } public class BearDaoImpl { @PersistenceContext(unitName="BearPU") protected EntityManager entityManager; -- } Checkout sample persistence.xml <?xml version="1.0" encoding="UTF-8"?> <persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">  <persistence-unit name="PolarPU" transaction-type="RESOURCE_LOCAL"> <

JPA 2 new feature @ElementCollection explained

@ElementCollection is new annotation introduced in JPA 2.0, This will help us get rid of One-Many and Many-One shitty syntax. Example 1: Stores list of Strings in an Entity @Entity public class Users implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ElementCollection private List<String> certifications = new ArrayList <String> (); public Long getId() { return id; } public void setId(Long id) { this.id = id; } public List <String> getCertifications() { return certifications; } public void setCertifications(List <String> certifications) { this.certifications = certifications; } .. } Users u = new Users(); u.getCertifications().add("Sun Certified Java Programmer"); em.persist(u); Generated Tables Users Co

Reuse JPA Entities as DTO

Note : Major design advantages of JPA Entities are they can detached and used across tiers and networks and later can by merged. Checkout this new way of querying entities in JPA 2.0 String ql = " SELECT new prepclass2.Employee (e.firstname, e.lastname) FROM Employee e "; List<Employee> dtos = em.createQuery(ql).getResultList(); The above query loads all Employee entities but with subset of data i.e. firstname, lastname. Employee entity looks like this. @Entity @Table(name="emp") public class Employee implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @Column private String firstname; @Column private String lastname; @Column private String username; @Column private String street; @Column private String city; @Column private String state; @Column private String zipc

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