Hibernate

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Hibernate
www.sunilos.com
www.raystec.com

Hibernate is ORM
Hibernate is an Object to Relational
Mapping Tool
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Object
ID NAME Salary
1 Ram 1000
2 Shyam 1100
3 Vijay 1200
4 Jay 1300
Object
Object
Object

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Object to Relational Mapping
USERS
oID
oFIRST_NAME
oLAST_NAME
oLOGIN_ID
oPASSWORD
public class User {
private int id = 0;
private String userId = null;
private String password = null;
private String firstName = null;
private String lastName = null;
public User(){}//Def Constructor
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
..Other Setter/Getter POJO (Plain Old Java
Object)
Data Transfer Object
(DTO)
Value Object ( VO)
• Class will become Table
• Attributes will become columns
• Instances will become Records

POJO
Are persistent classes.
Represent domain model.
Identifier Property (optional) has PK of a
table.
Must have default constructor.
Accessor methods will have naming
convention setName, getName, isName.
Properties need not to be public
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JDBC How to
conn.setAutoCommit(false);//Begin Trn
Statement stmt = conn.createStatement();
int i= stmt.executeUpdate(“INSERT into users
(id, first_name,
last_name,address,login_id,password)
VALUES (1,’Sunrays’,’technologies’,’South
Tukoganj’, ’sunrays’,’sun’)");
conn.commit(); //End Trn

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XML Mapping
 Readable metadata
 POJO / table mappings
 Attribute/Column
mapping
 Surrogate key
generation strategy
 Collection metadata
 Fetching strategies
 POJO and XML file
name must be same
and will be stored in
same folder
 XMLs should have
.hbm.xml extension
User.hbm.xml
<hibernate-mapping package=“in.co.sunrays.dto">
<class name="User" table=“ST_USER">
<id name="id" column="ID">
<generator class="increment" />
</id>
<property name="lastName" column="LAST_NAME" />
<property name="firstName" column="FIRST_NAME" />
<property name="address" column="STREET" />
<property name="userId" column="LOGIN_ID" />
<property name="password" />
</class>
</hibernate-mapping>

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Configuration :hibernate.cfg.xml
<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost/test</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>

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

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Configuration :hibernate.cfg.xml

<property name="show_sql">true</property>

<property name="hbm2ddl.auto">create</property>
<mapping resource=“in/co/sunrays/dto/User.hbm.xml" />
<mapping resource=“in/co/sunrays/dto/Role.hbm.xml" />
</session-factory>
</hibernate-configuration>

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Configuration
1. Create A Java Project from Eclipse
2. Add Hibernate Capabilities
3. Insert Database (MySQL) Driver into Build
Path
4. Create User.java
5. Create User.hbm.xml in same directory
with User.java
6. Keep hibernate.cfg.xml in the root
source folder

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TestUser - Add
public static void testAdd() throws Exception {
User pojo = new User ();
pojo.setFirstName("Dheeraj");
pojo.setLastName("Dubey"); //Prepare POJO
...
SessionFactory sessionFactory = new Configuration().configure()
.buildSessionFactory(); //Load Factory
Session s = sessionFactory.openSession(); //Create Session
Transaction tx = s.beginTransaction();
s.save(pojo); //Save POJO
tx.commit();
s.close();
}

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TestUser - Update
public static void testUpdate() throws Exception {
User pojo = new User ();
pojo.setId (4);
pojo.setFirstName("Dheeraj");
pojo.setLastName(“Upadhyay"); //Prepare POJO
...
s.update(pojo); //Update POJO
tx.commit();
s.close();
}

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TestUser - Delete
public static void testDelete() throws Exception {
User pojo= new User();
pojo.setId (4);
...
s.delete(dto); //Delete POJO
tx.commit();
s.close();
}

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TestUser - Get
public static void testGet() throws Exception {
SessionFactory sessionFactory =
new Configuration().configure().buildSessionFactory();
//Load Factory
User pojo = (User) s.get(User.class, 4);
System.out.println(pojo.getId());
System.out.println(pojo.getFirstName());….
s.close();
}

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Authenticate User
public User authenticate(String login, String pwd) throws
UserNotFoundException{
SessionFactory sessionFactory =
new Configuration().configure().buildSessionFactory();
Session s = sessionFactory.openSession();
Query q = s.createQuery(
"from User where userId = ? and password = ? ");
q.setString(0, login);
q.setString(1, pwd); Class
Name
Attributes

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Authenticate User
…
List list = q.list();
if (list.size() == 1) {
pojo = (User) list.get(0);
}else{
throw new
UserNotFoundException("login.invalid.user");
}
s.close();
return pojo;
}

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Get the list of Users
public static void testList() throws Exception {
.buildSessionFactory();
Query q = s.createQuery("from User");
List l = q.list();
Iterator it = l.iterator();
User pojo;
while (it.hasNext()) {
pojo = (User) it.next();
System.out.println(pojo.getId());
System.out.println(pojo.getFirstName());
}
s.close();
}

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Sequence Diagram
TestUser User SessionFactory
Hibernate.cfg
.xml
Session
User.hbm
.xml DB
Create&
setData
Configuration().
configure()
read
openSession
create
main
save(User)
read
INSERT INTO user VALUES(..)

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org.hibernate.Session
 createQuery – SELECT HQL statement
 save() – INSERT Statement
 update() – UPDATE Statement
 saveOrUpdate()
 delete() - DELETE Statement
 beginTransaction() – Returns transaction object
 createSQLQuery() – Create DB native SQL query
 load(dto.class, pk) - Loads record
o Throws exception if record does not exist
 get(dto.class, pk) - Get a record
o Returns null in case record does not exist
 flush() - synchronize object state with database

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More Interesting Methods
persist() – just like save()
merge()
lock()
refresh()
evict()
replicate()

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A single-threaded, short-lived object representing a
conversation between the application and the
persistent store.
Wraps a JDBC connection.
Factory for Transaction.
Holds a mandatory (first-level) cache of persistent
objects, used when navigating the object graph or
looking up objects by identifier.
Remove Object from First Level Cache
o session.evict(User)

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Architecture
Hibernate basically
sits between the DB
and application
Can map persistent
objects to tables
Application
Hibernate
Database
JDBC
hibernate.cfg.xml *.hbm.xml
Persistent Objects

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Hibernate
Hibernate is an object-relational mapping
tool (ORM) that allows for persisting Java
objects in a relational database.
Officially maintained by Jboss, Inc, started in
December, 2001
Opensource (LGPL)
Current Version is 3.2
Will be core of JBoss CMP 2.0 engine

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Why Hibernate
 Flexibility
 Handles all create-read-update-delete (CRUD)
database operations.
 (CRUD) operations using simple API; no SQL
 Generates DDL scripts to create DB schema (tables,
constraints, sequences)
 Flexibility to hand-tune SQL and call stored
procedures to optimize performance
 Database Independent
 Supports over 20 RDBMS; change the database by
tweaking configuration files
 Sits between the database and Java code, easy
database switch without changing any code

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Features
 Object oriented query language (HQL)
Portable query language, supports polymorphic queries
etc.
 Native SQL
You can also still issue native SQL, and also queries by
“Criteria” (specified using “parse tree” of Java objects)
 Transparent persistence
Allows easy saves/delete/retrieve for simple value objects
 Very high performance
“In general” due to intelligent (2-level) caching, although in
a few cases hand-written SQL might beat it

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Architecture

Hbm.xml Tags
Primary Key
Composite Key
Candidate Key
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Composite Key
 A PK may consists of multiple
columns Ex. Dept Code +
Employee Code
 Multiple properties are maped
for PK
 <composite-id> is used in place
of <id>
 A separate PK class is created
with composite attributes
 PK class must be serializable
and override equals() and
hascode() methods to compare
two primary keys.
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Session Factory
SessionFactory is created using config settings in
hibernate.cfg.xml
Ceate one Session Factory per database
Usually application has single SessionFactory
It is Thread Safe
It is immutable
It is Database Connection Pool
Optionally holds second-level cache

abc.cfg.xml
SessionFactory sessionFactory = new
Configuration().configure()
Configuration(“abc.cfg.xml”).configure()
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Auction Object Model Association
Multiplicity:-One Action Item
May have 0-n bids
Multiplicity:-One Action Item
May have 0-1 successful bid
AuctionItem
-id : int
-description
-bids:Set
-successfulBid:Bid
+getId
+setId
+getDescription
+setDescription
Bid
-id : int
-amount
-timestamp
-itemID
+getId
+setId
+getAmount
+setAmount
1 *
item bids
0..1
successfulBi
d
Composition

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Auction Table Structure
AuctionItem
ID DESCRIPTION
BID
ID AMOUNT TIMESTAMP ITEM_ID
PK
FK

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ActionItem
public class AuctionItem{
private long id;
private Set bids;
private String description;
private Bid successfulBid = null;
public Set getBids() {
return bids;
}
public void setBids(Set bids) {
this.bids = bids;
}
…..
}
POJO
JavaBean
Data Transfer
Object (DTO)
BO (Business
Object)
Domain Object
(DO)

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Bid
public class Bid{
private long id;
private int amount;
private String timestamp;
private long itemId;
public int getAmount() {
return amount;
}
public void setAmount(int amount) {
this.amount = amount;
………
}

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AuctionItem.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package=“in.co.sunrays..dto">
<class name="AuctionItem" table="AuctionItem">
<id name="id" column="ID"></id>
<property name="description" />
<set name="bids" cascade="all" lazy="true">
<key column="ITEM_ID" />
<one-to-many class="Bid" />
</set>
</class>
AuctionItem
-id : int
-description
-bids:Set
-successfulBid:Bid
+getId
+setId
+getDescription
+setDescription

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Bid.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-
3.0.dtd">
<hibernate-mapping package=“in.co.sunrays.dto">
<class name="Bid” table="BID">
<property name="amount“ />
<property name="timestamp" ” />
<property name=“itemId" column=“ITEM_ID”/>
</class>

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Add Auction
AuctionItem auctionItem = new AuctionItem();
auctionItem.setId(2);
auctionItem.setDescription("Auction 2");
Bid bid1 = new Bid();
bid1.setId(1);
bid1.setAmount(100);
bid1.setTimestamp("XXX"); ….
Set bids = new HashSet();
bids.add(bid1);
auctionItem.setBids(bids);

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Add Auction (Contd)
Configuration().configure().buildSessionFactory();
s.save(auctionItem);
tx.commit();
s.close();

One to One mapping
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Employee
-id : int
-firstNme
-lastName
- empAddr Address
+accessor
Address
-id : int
-street
-city
-state
+accessor
0..1
Employee.hbm.xml
<class name="Employee" table="Employee">
…
<one-to-one name="empAddr" cascade="all" class="Address“ />
</class>

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Dirty Check
 Retrieve an AuctionItem and change description
 String newDescription = “XYZ”;
 Session session = sessionFactory.openSession();
 Transaction tx = s.beginTransaction();
 AuctionItem item =
(AuctionItem) session.get(ActionItem.class, 1);
 item.setDescription(newDescription);
 tx.commit();
 session.close();

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Transitive Persistence
Retrieve an AuctionItem and create a new persistent Bid
 Bid bid = new Bid();
 bid.setId(1);
 bid.setAmount(bidAmount);
 Session session = sf.openSession();
 Transaction tx = session.beginTransaction();
 AuctionItem item=(AuctionItem) session.get(ActionItem.class, 1);
 Set s = item.getBids();
 s.add(bid);
 tx.commit();

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Detachment
Retrieve an AuctionItem and create a new persistent Bid
 Session session = sf.openSession();
 AuctionItem item =(AuctionItem) session.get(ActionItem.class, 1);
 item.setDescription(newDescription);
 Session session2 = sf.openSession();
 Transaction tx = session2.beginTransaction();
 session2.update(item);
 tx.commit();
 session2.close

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Object States

Object States
 Transient : The instance is not, and has never been associated
with any Session. It has no persistent identity (primary key
value).
 Persistent :The instance is currently associated with a Session. It
has a persistent identity (primary key value) and, perhaps, a
corresponding row in the database. For a particular Session,
Hibernate guarantees that persistent identity is equivalent to
Java identity (in-memory location of the object).
 Detached :The instance was once associated with a Session, but
that Session was closed, or the instance was serialized to
another process. It has a persistent identity and, perhaps, a
corresponding row in the database.
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Optimizing Data Access
Lazy Fetching ( On Demand )
o Load on demand
o <set name="bids" cascade="all" lazy="true">
Eager (Outer Join) Fetching
o <set name="bids" cascade="all" fetch="join">
o Load entire graph once
o Allows a whole graph of objects connected by many-to-
one, one-to-many, many-to-many and one-to-one
associations to be retrieved in a single SQL SELECT
Batch Fetching
o Hibernate retrieves a batch of entity instances or
collections in a single SELECT, by specifying a list of
primary keys or foreign keys.

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Transparent Lazy Fetching
AuctionItem item = (AuctionItem)
session.get(ActionItem.class, 1);
SELECT … FROM AUCTION_ITEM
WHERE ID = 1
Set bids = item.getBids().;
//Iterator iter = bids.iterate();
SELECT … FROM BID WHERE ITEM_ID
= ?

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Transparent Eager Fetching
AuctionItem item = (AuctionItem)
session.get(ActionItem.class, 1);
SELECT i.*, b.* FROM AUCTION_ITEM i,
BID b WHERE ITEM_ID = 1 AND
i.ID = b.ITEM_ID

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Exception Handling
It throws HibernateException
HibernateException is a unchecked
exception
 try {
 transaction = session.beginTransaction();
 session.save(sp);
 transaction.commit();
 } catch (HibernateException e) {
 transaction.rollback();
 } finally {
 }

Cascade
<one-to-one name="person" cascade=“all"/>
<one-to-one name="person"
cascade="persist,delete,lock"/>
For each basic operation of the Hibernate session -
including persist(), merge(), saveOrUpdate(),
delete(), lock(), refresh(), evict(), replicate() - there
is a corresponding cascade style. Respectively, the
cascade styles are named create, merge, save-
update, delete, lock, refresh, evict, replicate.
Special value : delete-orphan
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Cascade ( Cont. )
delete-orphan : applies only to one-to-many
associations, and indicates that the delete()
operation should be applied to any child
object that is removed from the association.
Cascade is recommended for <one-to-one>
and <one-to-many> but not for <many-to-
one> or <many-to-many> association
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HQL
 Q – Get all parts
 SQL - SELECT * FROM part;
 Query query = session.createSQLQuery(“SELECT * FROM part”);
 Query query = session.createQuery(“from Part”);
List list = query.list();
Iterator iter = list.iterator();
Part dto;
while (iter.hasNext()) {
dto =(Part)iter.next();
System.out.println(dto.getId() + "t" + dto.getName()+ "tt"
+dto.getColor());
}

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HQL -Get all grey parts
 SQL - SELECT * FROM part WHERE color like ‘Grey%’;
 Query query = session.createQuery(“from Part where color like ‘Grey
%’”);
List list = query.list();
Iterator iter = list.iterator();
Part dto;
while (iter.hasNext()) {
dto =(Part)iter.next();
System.out.println(dto.getId() + "t" + dto.getName()+ "tt"
+dto.getColor());
}

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HQL – Get some columns
 Q- Get all parts’ ids, names
 SELECT id, name FROM part;
 Query query = session.createQuery(“select p.id, p.name from Part p”);
 List rows = query.list();
 Iterator iter = rows.iterator();
 Object[] columns;
 System.out.println("IDtName");
 while (iter.hasNext()) {
o columns = (Object[])iter.next();
o Integer id = (Integer) columns[0];
o String name = (String) columns[1];
o System.out.println(id + "t" + name);
 }

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HQL-Joins
Q- Get parts with their City of Unit
SELECT part.id, name, color, unit.city
FROM part, unit WHERE unit.id =
part.unit_id;
Query query = session.createQuery(“select
p.id, p.name, p.color, u.city from Part p, Unit
u where p.unitId = u.id”);

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HQL – Order By
Q- Get all grey parts sorted by name
SQL – SELECT * FROM part WHERE color
like ‘Grey%’ ORDER BY name;
HQL – from Part where color like ‘Grey%’
order by name

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HQL - Aggregate Functions
Q- How many parts are there?
SELECT count(*) from part;
count(*) from Part”);
List rows= query.list();
Integer row = (Integer)rows.get(0);

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HQL – Group By
Q- Get parts’ color count
SQL – SELECT color,count(*) FROM part
GROUP BY color
p.color,count(*) from Part p group by
p.color”);

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Criteria
Q – Get all parts
SQL - SELECT * FROM part;
Query query = session.createQuery(“from
Part”);
Criteria crit =
session.createCriteria(Part.class);
List list = crit.list();

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Get all grey parts
SQL - SELECT * FROM part WHERE color
like ‘Grey%’;
Query query = session.createQuery(“from
Part where color like ‘Grey%’”);
Criteria crit =
crit.add(Restrictions.like(“color", “Grey%"));
crit.add(Restrictions.eq(“unitId", “2"));

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Criteria – selected attributes
Q- Get all parts’ ids, names
SELECT id, name FROM part;
HQL - select p.id, p.name from Part p
Criteria crit = session.createCriteria(Part.class);
ProjectionList p = Projections.projectionList();
p.add(Projections.property("id"));
p.add(Projections.property(“name"));
crit.setProjection(p);

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Criteria – Aggregate Functions
 Q- How many parts are there?
 SELECT count(id) from part;
 Query query = session.createQuery(“select count(id) from Part”);
 Criteria crit = session.createCriteria(Part.class);
o ProjectionList projList = Projections.projectionList();
o projList.add(Projections.count(“id"));
o projList.add(Projections. rowCount()); //count(*)
o projList.add(Projections.groupProperty(“color")); //Group by
o crit.setProjection(projList);
o List results = crit.list();
 Other Aggregate Function
o Projections.max
o Projections.min
o Projections.avg

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Criteria – AND Condition
Criteria crit =
crit.add(Restrictions.like(“color", “Grey%"));
crit.add(Restrictions.eq(“unitId", “2"));
Default is AND condition

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Criteria – OR Condition
 Criteria crit = session.createCriteria(Part.class);
 crit.add(Restrictions.or(
o Restrictions.like(“color", “Grey%"),
Restrictions.eq(“unitId", “2")
 );
 crit.add(Restrictions.or(
o Restrictions.eq(“name", “Nut") ,
o Restrictions.or(
 Restrictions.like(“color", “Grey%"), Restrictions.eq(“unitId", “2")
 );

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Criteria
Order By
o Criteria crit = session.createCriteria(Part.class);
o crit.add(Restrictions.like(“color", “Grey%"));
o Crit.addOrder( Order.asc(“name") );
o Crit.addOrder( Order.asc(“color") );
o Crit.addOrder( Order.dsc(“id") );
Get Max records
o crit.setMaxResults(10);
Get First few Record
o crit.setFirstResult(11)
Create Aliases
o crit.createAlias(“Part", “p")

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Criteria - Join
 Applying the restrictions becomes easy in the case of joins
as well. For example, the following query
 SELECT O.*, P.* FROM ORDERS O, PRODUCT P
WHERE
 O.ORDER_ID=P.ORDER_ID AND P.ID=’1111’;
 Would become
 List orders = session.createCriteria(Order.class);
 orders.setFetchMode(“products”,FetchMode.JOIN);
 orders.add(Restrictions.eq(“id”,”1111”));
 orders.list();

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Criteria – Group By
SELECT COUNT(ID) FROM ORDER HAVING
PRICETOTAL>2000 GROUP BY ID
 Can be rewritten in Criteria query as follows:
List orders = session.createCriteria(Order.class)
     .setProjection( Projections.projectionList()
      .add( Projections.count(“id”) )
       .add( Projections.groupProperty(“id”) )
     )
      .list();

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DetachedCriteria
 Some applications need to create criteria queries in
"detached mode", where the Hibernate session is not
available. This class may be instantiated anywhere, and
then a Criteria may be obtained by passing a session to
getExecutableCriteria(). All methods have the same
semantics and behavior as the corresponding methods of
the Criteria interface.

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DetachedCriteria
 DetachedCriteria dc =
DetachedCriteria.forClass(Student.class);
 dc.add( Restrictions.eq("name","Gavin King"));
 ........
 Session s1 = SessionFactory.openSession();
 dc.getExecutableCriteria(s1);
 List result = dc.list();
 s1.close();
 Session s2 = SessionFactory.openSession();
 dc.getExecutableCriteria(s2);
 result = dc.list();
 s2.close()

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Cache
 Caching is used to optimize database
applications.
 A cache reduces traffic between application
and the database by conserving data
already loaded from the database.
 The application may need to empty
(invalidate) the cache from time to time if
the database is updated in some way,
because it has no way of knowing whether
the cache is up to date.

Type of Cache
 Hibernate has 3 cache Level
o Query Cache
o First Level Cache
o Second Level Cache
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Query Cache
Query result sets may be cached. It is useful when
same queries are run frequently with the same
parameters.
To use the query cache enable it from
hibernate.cfg.xml by
<property
name="hibernate.cache.use_query_cache">
true </property>
query.list();
query.list(); //Same result will be fetched from Q
Cache

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Query Cache ( Cont. )
The query cache can be forcefully
refreshed by
query.setCacheMode(CacheMode.REFRESH ).
query.list();

First & Second Level Cache
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SessionFactory Object
Mandatory

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First Level Cache
Associated with Session object.
It is a transaction-level cache of persistent data. It is
used by default.
When an object is pass to save(), update() or
saveOrUpdate() and retrieved by load(), get(), list(),
iterate() or scroll(), that object is added to the
internal cache of the Session.
When flush() is subsequently called, the state of
that object will be synchronized with the database

Remove from 1st
Level
An object is removed from first level
cache using evict(dto) method.
Method clear() can be removed all
objects from first level cache.
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Second Level Cache
It is an optional cache and Stores objects across
session.
It is configured on a per-class and per-collection
basis. It can cache a class or a collection
An object is always searched in First-Level cache
before locating in Second-Level cache.

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Second Level Cache
Use <class-cache> and <collection-cache> elements
in hibernate.cfg.xml.
o <class-cache class="org.dto.Item" usage="read-write"/>
o <class-cache class="org.dto.Bid" usage="read-only"/>
o <collection-cache collection="org.dto.Item.bids"
usage="read-write"/>

Enable Second Level Cache
By default it is disabled , you can enable it in
hibernate.cfg.xml
<property
name="hibernate.cache.use_second_level_cache">
o true
</property>
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Named Queries
 <hibernate-mapping package=“in.co.sunrays.dto">
 <class name="User" table="users">
 <id name="id" column="ID">
 <generator class="increment" />
 </id>
 <property name="lastName" column="LAST_NAME" />
 <property name="firstName" column="FIRST_NAME" />
 <property name="address" column="STREET" />
 <property name="userId" column="LOGIN_ID" />
 <property name="password" column="PASSWORD" />
 </class>
 
 <query name="allUser">
 <![CDATA[ from User ]]>
 </query>
 </hibernate-mapping>

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Named Query (Contd)
SessionFactory sessionFactory = new
Configuration().configure()
.buildSessionFactory();
Session s = sessionFactory.openSession();
Query q = s.getNamedQuery("allUser");
List l = q.list();
Iterator it = l.iterator();

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Inheritance

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Inheritance
Payment
-id :long
-amount :float
-paymentType :String
CreditCardPayment
+ccType
Cash Cheque
+chqNumber
+bankName

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Table per class hierarchy
Payment
-PAYMENT_ID :LONG : PK
-AMOUNT : NUMBER
-PAYMENT_TYPE :VARCHAR
-CC_TYPE : VARCHAR
-CHQ_NUMBER : VARCHAR
-BANK_NAME : VARCHAR
SELECT payment_type, sum(amount) FROM Payment
GROUP BY payment_type

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Payment.hbm.xml
 <class name="Payment" table="PAYMENT">
 <id name="id" type="long" column="PAYMENT_ID">
 <generator class="native"/>
 </id>
 <property name="amount" column="AMOUNT"/>
 <discriminator column="PAYMENT_TYPE" type="string"/>
 ...
 <subclass name="CreditCardPayment" discriminator-
value="CREDIT">
 <property name=“ccType" column="CC_TYPE"/>
 ...
 </subclass>
 <subclass name="CashPayment" discriminator-value="CASH“>
 </subclass>

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Payment.hbm.xml (Cont)
 <subclass name="ChequePayment" discriminator-value="CHEQUE">
 <property name=“chqNumber " column=" CHQ_NUMBER"/>
 <property name=“bankName " column=" BANK_NAME"/>
 </subclass>
 </class>

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Add Payment
CreditCardPayment ccp = new
CreditCardPayment();
session.save(ccp);
ChequePayment cp = new ChequePayment();
session.save(cp);
CashPayment cp = new CashPayment();
session.save(cp);

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Get Payment
HQL = “from CreditCardPayment”
HQL = “from ChequePayment ”
HQL = “from CashPayment ”
HQL = “from Payment ”

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Table per subclass
PAYMENT
-AMOUNT : NUMBER
CREDIT_PAYMENT
-PAYMENT_ID :LONG : PK,FK
-CC_TYPE : VARCHAR
CASH_PAYMENT
CHEQUE_PAYMENT
-CHQ_NUMBER
-BANK_NAME

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Join Query
 Q: Get all ChequeNumbers
 select chq_number from cheque_payment
 Q: Get all Cheque Number and their amounts
 select chq_number, amount from Payment p,
cheque_payment cp
where p.payment_id = cp.payment_id
 select amount from Payment, cheque_payment where
payment.payment_id = cheque_payment.payment_id
 select sum(amount) from Payment, cheque_payment where
payment.payment_id = cheque_payment.payment_id

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Payment.hbm.xml
 </id>
 ...
 <joined-subclass name="CreditCardPayment"
table="CREDIT_PAYMENT">
 <key column="PAYMENT_ID"/>
 <property name="creditCardType" column="CCTYPE"/>
 ...
 </joined-subclass>

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Payment.hbm.xml
 <joined-subclass name="CashPayment"
table="CASH_PAYMENT">
 ...
 <joined-subclass name="ChequePayment"
table="CHEQUE_PAYMENT">
 ...
 </class>

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Table per subclass, using a
discriminator
PAYMENT
-PAYMENT_TYPE : VARCHAR
-AMOUNT : NUMBER
CREDIT_PAYMENT
-CC_TYPE : VARCHAR
CASH_PAYMENT
CHEQUE_PAYMENT
-CHQ_NUMBER
-BANK_NAME

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Payment.hbm.xml
 </id>
 <discriminator column="PAYMENT_TYPE" type="string"/>
 ...
 <subclass name="CreditCardPayment" discriminator-
value="CREDIT">
 <join table="CREDIT_PAYMENT">
 <property name="creditCardType" column="CCTYPE"/>
 </join>

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Payment.hbm.xml
 <subclass name="CashPayment" discriminator-value="CASH">
 <join table="CASH_PAYMENT">
 </subclass>

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Joins
Outer Join
Inner Join
Equ Joins
Left Join
Right Join

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Alternate Technologies
JDO – Java Data Object
EJB – CMP (Container Managed Persistence)
JPA (Java Persistence API)
TopLink
iBATIS
Note : No one replaces JDBC

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Assignment – Dealer Mgt

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Class Diagram
Dealer
-code : int
-name : String
-city : String
-distance : int
-hasLorry : String
-transporterId : int
-transporterName : String
-lorrySrNo:int
-lorryNo: String
+accessor
DealerService
+$add(Dealer)
+$update(Dealer)
+$delete(code)
+$get(code):Dealer
+getList():ArrayList
+search(Dealer):ArrayList
DealerTestCase
+$main()
DealerCtl
<<servlet>>
+doGet()
+goPost()

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Sequence Diagram - 1
DealerTestcase Dealer DealerService
Create&
setData
add(dto)
main
update(dto)
delete(dto)

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Sequence Diagram - 2
DealerCtl
<<servlet>>
Dealer DealerService
Create&
setData
add(dto)
submit
update(dto)
delete(dto)
DealerJSP

Disclaimer
This is an educational presentation to enhance the
skill of computer science students.
This presentation is available for free to computer
science students.
Some internet images from different URLs are used
in this presentation to simplify technical examples
and correlate examples with the real world.
We are grateful to owners of these URLs and
pictures.
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Thank You!
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