Sunday, 29 April 2012

Hibernate Introduction Part 1


So What is hibernate ?
Here is the answer
Click the following link
Link

:) Well, if you have time, just go thru each and understand. Otherwise, simply put, using hibernate
it is each save the data into the database or load the data from the database.

Well, let's start.

Step 1: Development environment

1. My sql server 5.0  Download
2. Hibernate 4.1.1 Download
3. JDBC Driver for Mysql ((mysql-connector-java-5.1.19.zip)) Download
4. Eclipse IDE

Unzip the hibernate buddle and you should have the following structure after you unzip
Documentation folder
lib Folder
Project folder
log text file
hibernate logo image
license text file


Step 2:

Open mysql and create the following table in any of the exisitng database or create new database.
Here is the script for our table


CREATE TABLE `patient`
(
           `ID` INT(11) NOT NULL AUTO_INCREMENT,
  `FirstName` VARCHAR(100) DEFAULT NULL,
    `LastName` VARCHAR(100) DEFAULT NULL,
           `Email` VARCHAR(200) DEFAULT NULL,
           PRIMARY KEY  (`ID`)
       ) ENGINE=INNODB DEFAULT


Step 3: Eclipse Java project

1. Click File -> New -> Other -> Java Project
2. Say Example1 for Project Name and leave all other to default values.
   (Make sure, JRE has been configured).
3. Next we will add all dependencies in the example1. Now click Example1 project in the project
   explorer and right click -> Click New-> Folder. Say folder name as lib

   Now copy the following files into lib folder
   (Eclipse project explorer accepts all copy and paste operation. For example, you can copy file
    or folder in windows explorer and then you can come back to eclipse project explorer and paste it)

     All the files in Hibernate->Lib->required.
     All the files in Hibernate->Lib->jpa.
     All the files in Hibernate->Lib->envers
     mysql-connector-java-5.1.18-bin.jar


4. Now  setup the build path. In order to execute our example, all the above jar files should be in
class build path

   Again, click on the Example1, right click, and select build Path->configure build path.
   Go to Libraries-> External jars,  browse lib folder you created earlier. Then add external jars by

 selecting all jar files that you copied to lib folder in one of previous step




Step 4: Creating Java beans

Now let us create the java bean for the patient where we want to store in the database.

Again, right click on Example1, Select New -> Class; Package Name : mypack and Class name :patient
Leave the all other to default values

Now type or copy the following

package mypack;

public class patient {

private Integer id;
private String firstName;
private String lastName;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getFirstName() {
return firstName;
}

public void setFirstName(String firstName) {
this.firstName = firstName;
}

public String getLastName() {
return lastName;
}

public void setLastName(String lastName) {
this.lastName = lastName;
}

}


Step 5: Mapping between Java bean and Table.

Let us first summarize what we have done so far. 1) My sql table 2) Java bean.

Now, important step, we will see how to map 1) and 2) , so that whenever new object is created,
it will insert one record in the database.


Hibernate makes persisting the state of your Java objects incredibly simple. However, in order for

Hibernate to know where to story your JavaBeans, or how to map the property of a JavaBean to a database

column, the developer has to provide a bit of direction to the Hibernate framework.

This is where the Hibernate mapping file comes into play. The mapping file tells Hibernate what table

in the database it has to access, and what columns in that table it should use.


Using JPA annotations also, we can do the same. In this example, first we will see using mapping files
and then we will convert the same example to JPA annotations.


Now let us create the mapping file
Right Click src->New->File. File Name as patient.hbm.xml

Type or copy the below content


<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Apr 29, 2012 6:48:24 PM by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping>
    <class name="mypack.patient" table="PATIENT">
        <id name="id" type="java.lang.Integer">
            <column name="ID" />
            <generator class="native" />
        </id>
        <property name="firstName" type="java.lang.String">
            <column name="FIRSTNAME" />
        </property>
        <property name="lastName" type="java.lang.String">
            <column name="LASTNAME" />
        </property>
    </class>
</hibernate-mapping>


Step 6 : Hibernate Configuration

Now we have the persistent class and its mapping file in place. Let’s configure Hibernate.

Right Click src->New->File. File Name as hibernate.hbm.xml

Paste following code there. Save it as hibernate.cfg.xml. Here you have to give the username,password

and database name according to your MySQL account.


<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
 "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost/sampledb</property>
<property name="connection.username">root</property>
<property name="connection.password">123</property>

<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>

<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>

<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>

<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>

<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">update</property>

<!-- Mapping files -->
<mapping resource="patient.hbm.xml" />

</session-factory>
</hibernate-configuration>


Step 7: Create Test class to store the objects

To create new class right click on "mypack" package and select New --> Class and give Name as Test.java

and paste the following code in class file.


package mypack;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.hibernate.HibernateException;

public class Test {

private static SessionFactory factory;
private static ServiceRegistry serviceRegistry;

public static void main(String[] args) {
try {
Configuration configuration = new Configuration();
configuration.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(
configuration.getProperties()).buildServiceRegistry();
factory = configuration.buildSessionFactory(serviceRegistry);
} catch (Throwable ex) {
System.err.println("Failed to create sessionFactory object." + ex);
throw new ExceptionInInitializerError(ex);
}
System.out.println("**Example : Hibernate 4 SessionFactory**");
System.out.println("----------------------------------------");

Session session = factory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
patient pt = new patient();
pt.setFirstName("John");
pt.setLastName("Smith");
session.saveOrUpdate(pt);
tx.commit();
} catch (HibernateException e) {
if (tx != null)
tx.rollback();
e.printStackTrace();
} finally {
session.close();
}
}
}


Now right click on test.java file and select Run as -> Java Application
If every thing configured correctly, then you will the see the following lines in the console at the
end

INFO: HHH000126: Indexes: [primary]
Apr 29, 2012 10:14:49 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000232: Schema update complete
**Example : Hibernate 4 SessionFactory**
----------------------------------------
Hibernate: insert into PATIENT (FIRSTNAME, LASTNAME) values (?, ?)

Now go to database and check records are inserted into patient table.


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