Intro 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 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 class Public 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(); } } }

Understanding the Architecture

Hibernate core interfaces Session SessionFactory Configuration Transaction Query Criteria Types

Configuring logging in Hibernate

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>

Link table structure EMP_TASKS table

Committing a database transaction

Understanding database transactions

HQL supports: WHERE clause ORDER BY clause GROUP BY clause All types of joins (inner, left outer, right outer, outer) Subquery etc

Other query types supported Query By Example Native SLQ query

Intro To Hibernate

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Intro To Hibernate