Introduction to Hibernate

Agenda Introduction to Hibernate Hibernate Architecture Persistence Lifecycle Object Identity Mapping tables to beans Mapping properties to columns Relationships Setting up a one to many relationships Setting up a many to many relationships Hibernate Transaction API Basic Queries Working with Queries Named Queries working with the query API Working with binding parameters

Plain JDBC

Simple example to insert a row into database table, using JDBC

public void insertRow(Employee emp) {

String insertSQL = “INSERT INTO emp values(….);

Connection conn = getConnectionFromPool();

Statement stmt = conn.createStatement(insertSQL);

stmt.execute();

}

Hibernate

Persistence for JavaBean/POJO Support for fine-grained, richly typed object

models Powerful queries Support for detached persistence objects Mapping meta data in XML file

Hibernate Configuration

The hibernate.properties file Used for hibernate configuration Contains

- Database configuration- Datasource configuration- Transaction configuration- Caching configuration- Connection pool configuration- Other settings

Hibernate Configuration... Contd

The hibernate.cfg.xml Alternative approach of configuration Can be used as replacement of

hibernate.properties Picked up from classpath Has got precedence on hibernate.properties file

Hibernate Configuration... Contd Non managed environment

<hibernate-configuration><session-factory>

<property name="hibernate.connection.driver_class"> COM.ibm.db2.jdbc.app.DB2Driver</property><property name="hibernate.connection.url">jdbc:db2:SAMPLE</property><property name="hibernate.connection.username">db2admin</property><property name="hibernate.connection.password">db2admin</property><property name="hibernate.connection.pool_size">10</property><property name="show_sql">true</property><property name="dialect">net.sf.hibernate.dialect.DB2Dialect</property><!-- Mapping files --><mapping resource="test_emp.hbm.xml"/>

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

Hibernate Configuration... Contd Managed environment (App Server)

<hibernate-configuration><session-factory>

<property name="hibernate.connection.datasource">java:comp/env/jdbc/my_ds1

</property><property name="hibernate.transaction.factory_class">

org.hibernate.transaction.CMTTransactionFactory</property><property name="hibernate.transaction.manager_lookup_class">

org.hibernate.transaction.WebSphereExtendedJTATransactionLookup</property>

<property name="show_sql">true</property> <property name="dialect">org.hibernate.dialect.DB2Dialect</property>

<mapping resource="emp.hbm.xml"/> <mapping resource="dept.hbm.xml"/>

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

Hibernate Mapping The hibernate-mapping xml file

<hibernate-mapping> <class name="com.entity.Emp" table="EMP"> <id name="empId" column="EMP_ID" > <generator class="native"></generator> </id> <property name="empName" column="EMP_NAME"></property> <property name="city" column="CITY"></property> <property name="deptId" column="DEPT_ID"></property> <property name="joinDate" column="JOIN_DATE"></property> <property name=“gender" column=“GENDER"></property> </class></hibernate-mapping>

Simple standalone hibernate appliation

Requirements Hibernate libraries Hibernate configuration file A POJO class A hibernate-mapping file A Main class

Sample POJO public class Emp implements SplEntity { private Integer empId; private String empName; private String city; private int deptId; private Date joinDate; private char gender;

public String getCity() { return city; } public void setCity(String city) { this.city = city; }

public int getDeptId() { return deptId; } public void setDeptId(int deptId) { this.deptId = deptId; }

public Integer getEmpId() { return empId; } public void setEmpId(Integer empId) { this.empId = empId; }

public String getEmpName() { return empName; } public void setEmpName(String empName) { this.empName = empName; }

public Date getJoinDate() { return joinDate; } public void setJoinDate(Date joinDate) { this.joinDate = joinDate; }

public char getGender() { return gender; } public void setGender(char gender) { this.gender = gender; } }

Sample Main classPublic class Main {

public static void main(String[] args) { try { SessionFactory factory = null; factory = new Configuration().configure().buildSessionFactory();

Session session = factory.openSession();Transaction tx = session.beginTransaction();

Emp e1 = new Emp();e1.setEmpName(“Rajesh B");e1.setCity(“Pune");e1.setDeptId(3);e1.setJoinDate(new Date("20-Jul-1995"));

session.save(e1);tx.commit();

} catch (Exception e) {e.printStackTrace();

}}

}

Hibernate Architecture

High Level View

Understanding the Architecture

Hibernate core interfaces

Session SessionFactory Configuration Transaction Query Criteria Types

Session Interface

SessionFactory Interface

Configuration Interface

Transaction Interface

Query and Criteria Interfaces

Configuring logging in Hibernate

Basic O/R Mapping

Hibernate-Mapping

Class Element

ID element

Composite ID Element

Built in Types

Mapping Collections

Persistent Collections

Emp model table relationship

Mapping Set

Lazy Initialization

Component Mapping

Dependent Object

Sample table definition

Employee-Address data model

Example of component mapping

Address class

Mapping Component

Mapping Associations

Associations

Many to one association

<class name="com.entity.Emp" table="EMP">

...

...

<many-to-one name="dept"

column="DEPT_ID"

class="Department"

not-null="true" />

</class>

Parent child relationship

<class name="com.entity.Dept" table="DEPT">......<set name="employees" inverse="true" cascade="all-delete-orphan"> <key column="DEPT_ID" /> <one-to-many class="Emp" />

</set></class>

One to one relationship

Employee-Person Object Dig

One to one association

<class name="com.entity.Emp" table="EMP">

...

...

<one-to-one name="person" class="Person" />

</class>

Many to many relationship

Link table structure

EMP_TASKS table

Many to many association

Manipulating Persistence Data

Persistence Lifecycle

Transient Objects

Persistent Objects

Detached Objects

Persistence Manager

Making an object persistent

Retrieving persistent object

Updating persistent object

Committing a database transaction

Transaction and Concurrency

Understanding database transactions

Hibernate Transaction API

JDBC Transactions

2 Phase Transactions

Hibernate Query LanguageHQL

Introduction to HQL

Query Interface

Binding Parameters

An example of simple Query

HQL supports:

WHERE clause ORDER BY clause GROUP BY clause All types of joins (inner, left outer, right outer,

outer) Subquery etc

Reporting Queries

Criteria Queries

Simple Criteria example

Other query types supported

Query By Example Native SLQ query

Cache

Mass Update/Deletes

Hibernate Cache Architecture

Hibernate First Level Cache

Hibernate Second Level Cache

Caching Strategies

Enabling Caching

Any Questions ?

Thanks !!!