ReLearn EveryThing: SIMPLE HIBERNATE EXAMPLE IN NETBEANS USING ORACLE

WHAT IS HIBERNATE?

Hibernate ORM (Hibernate in short) is an object-relational mapping library for the Java language, providing a framework for mapping an object-oriented domain model to a traditional relational database [1].

Hibernate's primary feature is mapping from Java classes to database tables (and from Java data types to SQL data types). Hibernate also provides data query and retrieval facilities. It generates SQL calls and relieves the developer from manual result set handling and object conversion. Applications using Hibernate are portable [1].

The Hibernate architecture is layered to keep you isolated from having to know the underlying APIs. Hibernate makes use of the database and configuration data to provide persistence services (and persistent objects) to the application [2].

Following is a very high level view of the Hibernate Application Architecture.

Figure 1 [2]

Persistent Objects

A persistent object is an object that has been assigned a storage location in a federated database. When you commit the transaction in which you create a persistent object, that object's data is saved in the database; the object can then be accessed by other processes. A persistent object continues to exist beyond the duration of the process that creates it. In contrast, a transient object exists only within the memory of the process that creates it; when that process terminates, the transient object ceases to exist [3].

Hibernate Objects

Configuration Object

The Configuration object is the first Hibernate object you create in any Hibernate application and usually created only once during application initialization. It represents a configuration or properties file required by the Hibernate.

SessionFactory Object

Configuration object is used to create a SessionFactory object which inturn configures Hibernate for the application using the supplied configuration file and allows for a Session object to be instantiated. The SessionFactory is a thread safe object and used by all the threads of an application.

You would need one SessionFactory object per database using a separate configuration file. So if you are using multiple databases then you would have to create multiple SessionFactory objects.

Session Object

A Session is used to get a physical connection with a database. The Session object is lightweight and designed to be instantiated each time an interaction is needed with the database. Persistent objects are saved and retrieved through a Session object.

Transaction Object

A Transaction represents a unit of work with the database and most of the RDBMS supports transaction functionality. Transactions in Hibernate are handled by an underlying transaction manager and transaction (from JDBC or JTA) [2].

MYGEDIZ EXAMPLE IN NETBEANS

Create Java Project

In netbeans, we create a new Java Project by choosing New Project choice under File Menu.
(Figure 2)

Figure 2

In displayed window we choose Java Category and Java Application Project. Then Next button is clicked. (Figure 3 )

Figure 3

Write Project name and if you don’t want to have main class automatically, you should unselect Create Main Class option. Then click Finish. We have created a Java Project. (Figure 4)

Figure 4

Add Required Library/Jar

MYGEDIZ Project will use Hibernate framework. So our first job is to add required libraries. Right over click Library directory. Select Add Library. (Figure 5)

Figure 5

Find Hibernate and Hibernate JPA in the list and add them. (Figure 6)

Figure 6

After that using Add JAR/Folder option, we add hibernate3.jar which is previously downloaded by us. You should download from http://www.java2s.com/Code/Jar/h/Downloadhibernate3jar.htm link. (Figure 7)

Figure 7

We should add ojdbc6.jar file too.

Design the Application

Now we can create new JFrame Form. Right Click over package – JFrame Form. Right class name and click Finish. (Figure 8)

Figure 8

We want to design a frame which is like Figure 9.

Figure 9

For this reason we add Tabbed Pane to frame and resize using arrow. We cover whole frame.
(Figure 10)

Figure 10

To add tab,select Panel and add to tabbed pane. Then resize again and cover the pane. (Figure 11)

Figure 11

Then right click over tab1 text to change tab name. For Examle first tab will be login tab. (Figure 12)

Figure 12

Now we add a Label to display message that shows which field will be used to enter username. Select label in palette and put int anywhere you want. Using little boxex you can resize easily. To change label name, double click and enter label script. (Figure 13)

Figure 13

Now we want to add text field. Select textfied from palette. Put it to panel. Right Click – Change variable name. Then give meaningfu variable name to use it easily while coding. Then again right click- edit text to delete jTextField1 text. Otherwise when application is run it will be displayed. (Figure 14)

Figure 14

Add password label and password field using requiered swings from palette. Then add button to click to login. Choose OK button from palette and again put it to panel. Change variable name and text. Then to give action double click on the button. Netbeans bring you tou source code of action of the button automatically.

Go on designing until reaching design like in Figure 9.

In this example we have login page to access the application. We have users whose responsibility is to add students, display, delete and update student information in mygediz system. So we need three tables. For one table users to hold username and password of all student affairs officers. For one table to hold students and the last one is to hold all phone numbers of students. Becuase each student may have one more than phone numbers. (Figure 15)

Figure 15

Design and Code Database Tables

Connect the database through SQLPlus or SQLDeveloper. Create all required tables with given properties.

Cretating Users Table

In users table our primary key will be username. Because it should be unique for each user. Instead of username, we may add new column as id to select as primary key and add unique constraint to username. But we prefer not to add extra column. We use username as primary key.

create table users (username varchar(20),password varchar(20),primary key(username));

We should add users to the database.

insert into users values('esra','123456');

insert into users values('said','111222');

Creating Students Table

create table students(

id int,

name varchar(20) not null,

surname varchar(20) not null,

department varchar(20),

gpa number(3,2),

primary key(id)

);

Creating Phones Table

Students may have one or more phone numbers. So we hold Phones table which will have auto incremented id column, stuId column which refers students table and shows which phone number is belong to which student. So stuId is foreign key for phones table.

create table phones (

id int,

stuId int,

phone varchar(10) not null,

foreign key (stuId) references students,

primary key(id)

);

In Oracle to provide auto_increment we have to create sequence and trigger. In phones table we want to start id with 1 and increment it by 1.

CREATE SEQUENCE phone_seq MINVALUE 1

START WITH 1

INCREMENT BY 1

CACHE 20;

CREATE OR REPLACE TRIGGER phone_auto_increment

BEFORE INSERT ON phones

for each row

begin

select phone_seq.nextval into :new.id from dual;

end;

Creating Java Classes

For each table we have to create a java class that is used to map. After the other configurations are done, we can insert, delete, update any record as easily as creating java objects. We have three tables : Users, Students, Phones. So we create three Java classes.

User.java

Under datapack package, we create User.java class. In Uers table we have two columns whose names are userName and password respectively. So in java class we create two fields to be used mapping of these columns. We have to generate getter and setter methods. Because hibernate needs them. To generate getter and setter methods in netbeans automatically, right click over editor -> Insert code -> Getter and setter. (Figure 16)

Figure 16

package datapack;

public class User {

private String userName;

private String password;

public String getUserName() {

return userName;

}

public void setUserName(String userName) {

this.userName = userName;

}

public String getPassword() {

return password;

}

public void setPassword(String password) {

this.password = password;

}

Student.java

Again under datapack package, we create Student.java class. Our student has id, name, surname, department, gpa information. So we use these columns’ name and write as attributes in this class. We can give different names but to facilitate our job, we use same names. In this scenario Students and Phones tables have one-to-many relation. It means one student may have zero or more phone numbers. Likewise a phone number can be just mapped to one student and many phone numbers can be mapped to one student. To be able to access phone numbers in student object we have to declare one-to-many relation in mapping file. To hold many phone numbers, we have to declare a java data structure. So we declare Set<Phone> phones attribute.

package datapack;

import java.util.HashSet;

import java.util.Set;

import javax.persistence.Column;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.Table;

/**

* @author esranur.galip

/*We can use annotations of J(ava)P(ersistence)A(pi) to Show which attribute is mapped to which column of table */

@Entity

@Table(name = "STUDENTS")

public class Student {

@Id

@Column(name = "id")

private int id;

@Column(name = "name")

private String name;

@Column(name = "surname")

private String surname;

@Column(name = "gpa")

private double gpa;

@Column(name = "department")

private String department;

private Set<Phone> phones = new HashSet<Phone>();

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getSurname() {

return surname;

}

public void setSurname(String surname) {

this.surname = surname;

}

public double getGpa() {

return gpa;

}

public void setGpa(double gpa) {

this.gpa = gpa;

}

public String getDepartment() {

return department;

}

public void setDepartment(String department) {

this.department = department;

}

public Set<Phone> getPhones() {

return phones;

}

public void setPhones(Set<Phone> phones) {

this.phones = phones;

}

public String toString() {

String text = "Id\tName\tSurname\tDepartment\tGpa\tPhones\n";

text += id + "\t" + name + "\t" + surname + "\t" + department + "\t" + gpa;

for (Phone p : phones) {

text += "\t" + p.getNumber();

}

text += "\n";

return text;

}

We write toString method to be able to use when a student’s information is displayed. We add all values to text variable by formatting tabs. Then we add phone information by traversing the phones list. Because of list object type is Phone, in for loop condition we can declare Phone p varible and assign phones list to the variable. So in each iteration p variable will have one phone value. In for loop we add phone number to text variable.

Phone.java

Phones table has id, stuId and phone columns. stuId is foreign key and refers to students table. As we said before we have one-to-many relation between students and phones tables. So to provide this mapping we added hashset of phones in student java class. In phone class we declare student referans as attribute to relate phone to student.

package datapack;

/**

* @author esranur.galip

public class Phone {

private int id;

private Student student;

private String number;

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getNumber() {

return number;

}

public void setNumber(String number) {

this.number = number;

}

public Student getStudent() {

return student;

}

public void setStudent(Student student) {

this.student = student;

}

After creating all classes I want to add addPhone method to Student java class to facilitate to add phone information. Because before adding new phone number, we have to set student attribute of that phone after that we add that phone to student’s phone list.

public void addPhone(Phone phone) {

phone.setStudent(this);

phones.add(phone);

}

After adding this method Student java class is this :

package datapack;

import java.util.HashSet;

import java.util.Set;

import javax.persistence.Column;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.Table;

/**

* @author esranur.galip

/*We can use annotations of J(ava)P(ersistence)A(pi) to Show which attribute is mapped to which column of table */

@Entity

@Table(name = "STUDENTS")

public class Student {

@Id

@Column(name = "id")

private int id;

@Column(name = "name")

private String name;

@Column(name = "surname")

private String surname;

@Column(name = "gpa")

private double gpa;

@Column(name = "department")

private String department;

private Set<Phone> phones = new HashSet<Phone>();

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getSurname() {

return surname;

}

public void setSurname(String surname) {

this.surname = surname;

}

public double getGpa() {

return gpa;

}

public void setGpa(double gpa) {

this.gpa = gpa;

}

public String getDepartment() {

return department;

}

public void setDepartment(String department) {

this.department = department;

}

public Set<Phone> getPhones() {

return phones;

}

public void addPhone(Phone phone) {

phone.setStudent(this);

phones.add(phone);

}

public void setPhones(Set<Phone> phones) {

this.phones = phones;

}

public String toString() {

String text = "Id\tName\tSurname\tDepartment\tGpa\tPhones\n";

text += id + "\t" + name + "\t" + surname + "\t" + department + "\t" + gpa;

for (Phone p : phones) {

text += "\t" + p.getNumber();

}

text += "\n";

return text;

}

Implementation

Configuration of Hibernate Files

Hibernate.cfg.xml

To connect to the database and find the required mapping files we have to create hibernate configuration file. I prefer to collect all hibernate files under hibernatepacks. So first we create hibernatepacks package. Then to create the configration file, right click over package, select Hibernate Configuration Wizard. (Figure 17, 18, 19)

Figure 17

Figure 18

Figure 19

NetBeans automatically generates configuration file. But we need modification. (Figure 20)

Figure 20

To modify the code we select the Source tab and we reach the source code. We change dialect as Oracle10gDialect. Then we add password information and to display each transaction’s sql code in the console we add Show_sql property. (Figure 21)

Figure 21

Users.hbm.xml

For each table in our database, we prefer to create a class and hibernate mapping file. Mapping file provides us to map each column to each attribute of class. To create new Hibernate mapping file, right click over desired package, select Hibernate Mapping Wizard. (Figure 22)

Figure 22

After giving name of file, we will select the table whose mapping file is being created. (Figure 23)

Figure 23

Then to select related class for mapping, click … button. Write class name into search field and find the related class, add the class. (Figure 24)

Figure 24

We will do mapping between hibernate-mapping tags. First we write class tag that declares which class mapping is being done. name keyword in class tag we give path of mapped class. Student java class is under datapack package. Then in table keyword we give mapped table name. Between id tags we declare our primary key column of our table. For other columns and attributes we use property tag. name keyword in property tag specifies attribute name of class. name keyword in column tag specifies related column name. (Figure 25)

Figure 25

After creating each hbm.xml file we have to add it to hibernate configure file. Hibernate Mapping Wizard does this operation as soon as cerating mapping file. If you don’t use Hibernate framework, you should do it manually. (Figure 26)

Figure 26

Students.hbm.xml

Here we have different tag set. This set tag is used to map phones hash set in Student java class. As doing this we specify that in Phones table find all tuples whose stuId column is equal to id of this student. So name keyword in set tag specifies hash set name in Student table. Table keyword is declaring table name that holds student’s phone number(s). Then with one-to-many tag we declare class name of phones table.

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

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

<class name="datapack.Student" table="STUDENTS">

</id>

</property>

</property>

</property>

</property>

<key>

</key>

<one-to-many class="datapack.Phone" />

</set>

</class>

</hibernate-mapping>

Phones.hbm.xml

In phones table we created trigger to increment id automatically. Here we declare this using generator keyword. To map student attribute whose type is Student java class we use many-to-one tag. name keyword in the tag declare student attribute of Phone java class. class keyword is path of Student java class.

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

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

<class name="datapack.Phone" table="PHONES">

</id>

<many-to-one name="student" class="datapack.Student" cascade="all"> <column name="stuId" not-null="true" />

</many-to-one>

</property>

</class>

</hibernate-mapping>

Last status of hibrerbate.cfg.xml

Figure 27

HibenateUtility.java

After writing configuration and mapping files, to run code we have to create session to connect to the database. So we first get instance of Sessionfactory by configuring hibernate.cfg.xml file. This operation is done just one time. Because SessionFactory is heavyweight. Using session factory we openSession. For each database we have to create new session. For each transanction we have to begin transaction. Note that commit the transaction and at the end of the application don’t forget to close session. For this creating ang getting instance operations we prefer to create HibenateUtility class under datapack package.

package datapack;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.Transaction;

import org.hibernate.cfg.Configuration;

/**

* @author esranur.galip

public class HibernateUtility {

private SessionFactory sessionFactory;

private Session session;

private Transaction tx;

public void configureSession() {

sessionFactory = (SessionFactory) new Configuration().configure("/hibernatepacks/hibernate.cfg.xml").buildSessionFactory();

}

public Session openSession() {

session = sessionFactory.openSession();

return session;

}

public Transaction beginTransaction() {

tx = session.beginTransaction();

return tx;

}

GUI.java

Here we have a part of GUI java class code. Here we create an object of HibernateUtility class and we call configureSession() method of it in constructor. Then we disabled all tabbes except Login tab. Because if user can login successfully, then we want to display contents of other tabs.

package mygediz;

import datapack.HibernateUtility;

import datapack.Phone;

import datapack.Student;

import datapack.User;

import org.hibernate.Session;

import org.hibernate.Transaction;

public class Gui extends javax.swing.JFrame {

private HibernateUtility utility;

public Gui() {

initComponents();

utility = new HibernateUtility();

utility.configureSession();

jTabbedPane1.setEnabledAt(1, false);

jTabbedPane1.setEnabledAt(2, false);

jTabbedPane1.setEnabledAt(3, false);

jTabbedPane1.setEnabledAt(4, false);

}

/* GUI components’ construction methods here… */

…

private void loginButtonActionPerformed(java.awt.event.ActionEvent evt) {

User user;

/*Open session and beginTransaction using utility’s methods */

Session session = utility.openSession();

Transaction tx = utility.beginTransaction();

/*Check whether user entered userName and password or not, if entered, using session object’s get method we can find any record from table as object giving it’s id as parameter.*/

if (!userName.getText().equals("") && !password.getText().equals("")) {

user = (User) session.get(User.class, userName.getText());

tx.commit();

/*if user is null, it means we have no record about user whose userName is equal to userName that was entered by user */

if (user == null) {

loginMessage.setText("Invalid userName");

}

/*If user is not null, it means we have an user whose userName is equal to userName that was entered by user, we check the password whether user object’s password is equal to password that was entered by user or not. As said before using get method of session we get all record values from table to user object. If it is not equal we display Invalid password message */

else if (!user.getPassword().equals(password.getText())) {

loginMessage.setText("Invalid password");

}

/* If it equals, we display success message and enable all tabs. */

else {

loginMessage.setText("Success");

jTabbedPane1.setEnabledAt(1, true);

jTabbedPane1.setEnabledAt(2, true);

jTabbedPane1.setEnabledAt(3, true);

jTabbedPane1.setEnabledAt(4, true);

}

/* If user didn’t enter a value or directly click to login button, we display “Enter password” message */

else {

loginMessage.setText("Please enter userName/password");

}

session.close();

}

private void addButtonActionPerformed(java.awt.event.ActionEvent evt) {

/*Open session and beginTransaction using utility’s methods */

Session session = utility.openSession();

Transaction tx = utility.beginTransaction();

/*We want to add new student. Values are entered y user using gui components. So first we create a student object. Then we set all values according to user entered values. */

Student newStudent = new Student();

newStudent.setId(Integer.parseInt(id.getText()));

newStudent.setName(name.getText());

newStudent.setSurname(surname.getText());

newStudent.setDepartment(department.getText());

newStudent.setGpa(Double.parseDouble(gpa.getText()));

/* We just use save method of session object*/

session.save(newStudent);

/*Don’t forget to call commit methdo of transaction */

tx.commit();

session.close();

addMessage.setText("Success");

}

/* This method is written to find student record giving it’s id */

public Student getStudent(Session session, int id) {

Student student = (Student) session.get(Student.class, id);

return student;

}

private void updateButtonActionPerformed(java.awt.event.ActionEvent evt) {

/*Open session and beginTransaction using utility’s methods */

Session session = utility.openSession();

Transaction tx = utility.beginTransaction();

/* find user using previously written getStudent method*/

Student updatedStudent = getStudent(session, Integer.parseInt(updateId.getText()));

if (updatedStudent == null) {

updateMessage.setText("Wrong id");

} else {

/*If we have that student we can add new phone.*/

Phone newPhone = new Phone();

newPhone.setNumber(updatePhone.getText());

updatedStudent.addPhone(newPhone);

/*Just call saveOrUpdate or just update method of session */

session.saveOrUpdate(updatedStudent);

/*Don’t forget to call commit method of transaction */

tx.commit();

updateMessage.setText("Success");

}

session.close();

}

private void displayButtonActionPerformed(java.awt.event.ActionEvent evt) {

/*Open session using utility’s method */

Session session = utility.openSession();

/* Find student */

Student displayedStudent = getStudent(session, Integer.parseInt(displayId.getText()));

if (displayedStudent == null) {

displayArea.setText("Wrong id");

} else {

/*Just paste information of student to displayArea */

displayArea.setText(displayedStudent.toString());

}

session.close();

}

private void deleteButtonActionPerformed(java.awt.event.ActionEvent evt) {

/*Open session and beginTransaction using utility’s methods */

Session session = utility.openSession();

Transaction tx = utility.beginTransaction();

Student deletedStudent = getStudent(session, Integer.parseInt(deleteId.getText()));

if (deletedStudent == null) {

deleteMessage.setText("Wrong id");

} else {

/* call delete method of session */

session.delete(deletedStudent);

tx.commit();

deleteMessage.setText("Success");

}

session.close();

}

/* Main class and attributes here */

…

}

Easy Way

Instead of creating mapping file for each table, we can create just one mapping file. Between hibernate-mapping tags, for each class we write class tag. Mappings are done between class tags for each table. In hibernate.cfg.xml, insetead of writing 3 mapping files, we just write one mapping file. Because this file contains all mappings.

Hibernate.cfg.xml

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

<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

<session-factory>

<property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>

<property name="hibernate.connection.driver_class">oracle.jdbc.OracleDriver</property>

<property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:XE</property>

</session-factory>

</hibernate-configuration>

Mappings.hbm.xml

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

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

</property>

</class>

</id>

</property>

</property>

</property>

</property>

<key>

</key>

<one-to-many class="datapack.Phone" />

</set>

</class>

</id>

<many-to-one name="

student" class="datapack.Student" cascade="all">

</many-to-one>

</property>

</class>

</hibernate-mapping>

REFERENCES

[1] : “Hibernate (Java)”, http://en.wikipedia.org/wiki/Hibernate_(Java)

[2] : “Hibernate Tutorial”, http://www.tutorialspoint.com/hibernate/hibernate_architecture.htm

[3] : “Persistent Objects”, http://wwwasd.web.cern.ch/wwwasd/lhc++/Objectivity/V5.2/Java/guide/jgdPersistence.fm.html

[4] : “Hibernate Community Documentation”, http://docs.jboss.org/hibernate/orm/4.2/devguide/en-US/html/ch01.html

ReLearn EveryThing

Pages

Saturday, May 17, 2014

SIMPLE HIBERNATE EXAMPLE IN NETBEANS USING ORACLE

WHAT IS HIBERNATE?

Persistent Objects

Hibernate Objects

Configuration Object

SessionFactory Object

Session Object

Transaction Object

MYGEDIZ EXAMPLE IN NETBEANS

Create Java Project

Add Required Library/Jar

Design the Application

Design and Code Database Tables

Cretating Users Table

Creating Students Table

Creating Phones Table

Creating Java Classes

User.java

Student.java

Phone.java

Implementation

Configuration of Hibernate Files

Hibernate.cfg.xml

Users.hbm.xml

Students.hbm.xml

Phones.hbm.xml

Last status of hibrerbate.cfg.xml

HibenateUtility.java

GUI.java

Easy Way

Hibernate.cfg.xml

Mappings.hbm.xml

REFERENCES

No comments:

Post a Comment