generator-blog.notes

hibernate.notes

Hibernate is an object-relational persistence framework which maps plain old Java objects (POJOs) to relational database tables, and transforms the data from one representation to the other.

Metadata (specified using annotations or XML) maps the fields of a class to the columns of a table so that a persisted instance of the class is represented by a row in the table.

The SQL required to update and query the database is automatically generated by Hibernate, so the developer no longer needs to write repetitive CRUD style SQL statements by hand.

Hibernate consists of these components:

Metadata to describe the mapping between classes and tables.
An API for CRUD operations on the objects of persistent classes.
A query language and API.
Transaction management and optimization functions.

Hibernate 3.5+ implements the Java Persistence API (JPA) 2.0 specification.

using-lishys-notes.notes

Guide

The guide pane on the right contains information organized into sections.

Use the previous section

and

buttons to move through the sections, or click an accordion tab (shown below) to go directly to a particular topic.

Code Reference

Each paragraph in the guide is usually associated with a particular piece of code. An orange arrow indicates that the code displayed in the middle pane is relevant to the guide text.

If the arrow is gray, simply click anywhere on the paragraph and the relevant code will be displayed.

Code Highlighter

The highlight feature identifies areas of the code which relate to a word or term in the guide. Hover the mouse over any underlined word and the relevant code will be highlighted.

next section

You can disable the highlighting feature at any time by clicking on the

button.

Don't forget to make the appropriate code page visible by clicking on any paragraph with a gray arrow.

world-entities.jpg

world-schema.png

create-city.sql

CREATE TABLE city (
  city_id         NUMBER,
  city_name       VARCHAR2(50)  NOT NULL,
  ctry_id         NUMBER        NOT NULL,
  CONSTRAINT city_pk  PRIMARY KEY (city_id),
  CONSTRAINT city_fk1 FOREIGN KEY (ctry_id) REFERENCES ctry
  
);

CREATE SEQUENCE city_seq1;
CREATE OR REPLACE TRIGGER city_trg1
  BEFORE INSERT ON city FOR EACH ROW
BEGIN 
    IF :NEW.city_id IS NULL THEN
      SELECT city_seq1.NEXTVAL INTO :NEW.city_id FROM DUAL;
    END IF;
END;
/

INSERT INTO city (city_name, ctry_id)  VALUES('Berlin', 1);
INSERT INTO city (city_name, ctry_id)  VALUES('Hamburg', 1);
INSERT INTO city (city_name, ctry_id)  VALUES('Munich', 1);
INSERT INTO city (city_name, ctry_id)  VALUES('Accra', 2);
INSERT INTO city (city_name, ctry_id)  VALUES('Kumasi', 2);
INSERT INTO city (city_name, ctry_id)  VALUES('Tamale', 2);
INSERT INTO city (city_name, ctry_id)  VALUES('Aukland', 6);
INSERT INTO city (city_name, ctry_id)  VALUES('Christchurch', 6);
INSERT INTO city (city_name, ctry_id)  VALUES('Wellington', 6);
COMMIT;

create-continent.sql

CREATE TABLE cont (
  cont_id         NUMBER,
  cont_name       VARCHAR2(50)  NOT NULL,
  CONSTRAINT cont_pk  PRIMARY KEY (cont_id),
  CONSTRAINT cont_uk1 UNIQUE (cont_name)
);

CREATE SEQUENCE cont_seq1;
CREATE OR REPLACE TRIGGER cont_trg1
  BEFORE INSERT ON cont FOR EACH ROW
BEGIN 
    IF :NEW.cont_id IS NULL THEN
      SELECT cont_seq1.NEXTVAL INTO :NEW.cont_id FROM DUAL;
    END IF;
END;
/

INSERT INTO cont (cont_name) VALUES('Africa');
INSERT INTO cont (cont_name) VALUES('Asia');
INSERT INTO cont (cont_name) VALUES('Europe');
INSERT INTO cont (cont_name) VALUES('North America');
INSERT INTO cont (cont_name) VALUES('South America');
INSERT INTO cont (cont_name) VALUES('Oceania');
INSERT INTO cont (cont_name) VALUES('Antarctica');
COMMIT;

create-country.sql

CREATE TABLE ctry (
  ctry_id         NUMBER,
  ctry_name       VARCHAR2(50)  NOT NULL,
  ctry_area       NUMBER        NOT NULL,
  ctry_pop        NUMBER        NOT NULL,
  cont_id         NUMBER        NOT NULL,
  CONSTRAINT ctry_pk  PRIMARY KEY (ctry_id),
  CONSTRAINT ctry_uk1 UNIQUE (ctry_name),
  CONSTRAINT ctry_fk1 FOREIGN KEY (cont_id) REFERENCES cont
  
);

CREATE SEQUENCE ctry_seq1;
CREATE OR REPLACE TRIGGER ctry_trg1
  BEFORE INSERT ON ctry FOR EACH ROW
BEGIN 
    IF :NEW.ctry_id IS NULL THEN
      SELECT ctry_seq1.NEXTVAL INTO :NEW.ctry_id FROM DUAL;
    END IF;
END;
/

INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('Germany', 137847, 82046000, 3);
INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('Ghana', 92098, 23837000, 1);
INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('Australia', 2966200, 21884000, 6);
INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('Greece', 50949, 11257285, 3);
INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('Georgia', 26900, 4382100, 3);
INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('New Zealand', 104454, 4320300, 6);
INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('Gambia', 4361, 1705000, 1);
INSERT INTO ctry (ctry_name, ctry_area, ctry_pop, cont_id)
  VALUES('Gabon', 103347, 1475000, 1);
COMMIT;

create-world.sql

@reset-world.sql
@create-continent.sql
@create-country.sql
@create-city.sql

reset-world.sql

DROP TABLE city;
DROP TABLE ctry;
DROP TABLE cont;

DROP SEQUENCE cont_seq1;
DROP SEQUENCE ctry_seq1;
DROP SEQUENCE city_seq1;

City.java

package com.lishman.world.domain;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.SequenceGenerator;

@Entity
public class City implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "CITY_ID_GENERATOR", sequenceName = "CITY_SEQ1")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "CITY_ID_GENERATOR")
    @Column(name = "CITY_ID")
    private Integer id;

    @Column(name = "CITY_NAME")
    private String name;

    @ManyToOne
    @JoinColumn(name = "CTRY_ID")
    private Country country;

    public City() {
    }

    public Integer getId() {
        return this.id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return this.name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Country getCountry() {
        return this.country;
    }
    public void setCountry(Country country) {
        this.country = country;
    }

}

Continent.java

package com.lishman.world.domain;

import java.io.Serializable;
import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;

@Entity
@Table(name = "CONT")
public class Continent implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "CONT_ID_GENERATOR", sequenceName = "CONT_SEQ1")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "CONT_ID_GENERATOR")
    @Column(name = "CONT_ID")
    private Integer id;

    @Column(name = "CONT_NAME")
    private String name;

    @OneToMany(mappedBy = "continent")
    private Set<Country> countries;

    public Continent() {
    }
    public Integer getId() {
        return this.id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return this.name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Country> getCountries() {
        return this.countries;
    }
    public void setCountries(Set<Country> countries) {
        this.countries = countries;
    }

}

Country.java

package com.lishman.world.domain;

import java.io.Serializable;
import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;

@Entity
@Table(name = "CTRY")
public class Country implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "CTRY_ID_GENERATOR", sequenceName = "CTRY_SEQ1")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "CTRY_ID_GENERATOR")
    @Column(name = "CTRY_ID")
    private Integer id;

    @Column(name = "CTRY_AREA")
    private Integer area;

    @Column(name = "CTRY_NAME")
    private String name;

    @Column(name = "CTRY_POP")
    private Integer population;

    @OneToMany(mappedBy = "country")
    private Set<City> cities;

    @ManyToOne
    @JoinColumn(name = "CONT_ID")
    private Continent continent;

    public Country() {
    }

    public Integer getId() {
        return this.id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public Integer getArea() {
        return this.area;
    }
    public void setArea(Integer area) {
        this.area = area;
    }
    public String getName() {
        return this.name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getPopulation() {
        return this.population;
    }
    public void setPopulation(Integer population) {
        this.population = population;
    }
    public Set<City> getCities() {
        return this.cities;
    }
    public void setCities(Set<City> cities) {
        this.cities = cities;
    }
    public Continent getContinent() {
        return this.continent;
    }
    public void setContinent(Continent continent) {
        this.continent = continent;
    }
}

ContinentAccess.java

package com.lishman.world;

import javax.persistence.EntityManager;
import javax.persistence.Persistence;

import com.lishman.world.domain.Continent;
import com.lishman.world.domain.Country;

public class ContinentAccess {
    
    public static void main(String[] args) {
        
        EntityManager em = Persistence
                            .createEntityManagerFactory("world")
                            .createEntityManager();
                
        // find
        Continent europe = em.find(Continent.class, 3);
     
        Country ghana = em.find(Country.class, 2);
        String name = ghana.getContinent().getName();
        
        
        // persist
        em.getTransaction().begin();    
   
        Continent cont = new Continent();
        cont.setName("New Continent");
        em.persist(cont);
        int contId = cont.getId();

        em.getTransaction().commit();

        
        // update
        em.getTransaction().begin();

        Continent oceania = em.find(Continent.class, 6);
        oceania.setName("Australasia");

        em.getTransaction().commit();

        
        // remove
        em.getTransaction().begin();

        Continent newCont = em.find(Continent.class, contId);
        em.remove(newCont);

        em.getTransaction().commit();
        
        
        em.close();

    }
}

orm.xml

<?xml version="1.0" encoding="UTF-8"?>

<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
                 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 version="1.0"
                 xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_1_0.xsd">
</entity-mappings>

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             version="1.0"
             xsi:schemaLocation="
           http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
                
  <persistence-unit name="world">

    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    
    <class>com.lishman.world.domain.Country</class>
    <class>com.lishman.world.domain.Continent</class>
    <class>com.lishman.world.domain.City</class>
    
    <properties>
        <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/>
        <property name="hibernate.connection.url" value="jdbc:oracle:thin:@my_server:1521:my_db"/>
        <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/>
        <property name="hibernate.connection.username" value="my_user"/>
        <property name="hibernate.connection.password" value="my_password"/>
        <property name="hibernate.show_sql" value="true"/>
        <property name="hibernate.format_sql" value="true"/>
    </properties>
    
  </persistence-unit>
</persistence>

Guide

Code Reference

Code Highlighter

Entities

Entity Manager

Configuration