Hibernate java and_oracle

copyright 2006, rhinosystemsinc.com all rights re
What we'll Cover
• Introduction of HibernateV3
Configuration & Setup of Hibernate/Java
• Code
• Pros and Cons
• RESOURCES
• Q & A.

Intro:About Hibernate
• www.hibernate.org - Open Source since, and
now with JBoss (since late 2003)
w/ commercial support & training.
Founder: Gavin King
• Provides a layer for java to interact with the
database.
– Is technically a set of java-class libraries that you use to
gain access to your database
• Hibernate caches database objects
– & Hibernate services your Java program
1/3

• Hibernate layer resides in your JVM.
• Improves performance
– objects are cached in JVM and mapped to your
object model.
• Used in commercial applications
– JBoss for one (yes, another open source…)
– Many more opensource and commercial listed at:
http://www.hibernate.org/27.html
2/3

• Hibernate is highly customizable
– Caching (2nd
level cache).
– Database dialects
– Transaction
– Connection pooling
– Custom Types
• Or use out of box (recommend changing: connection pooling).
3/3

Intro:Importance of DAO
• DAO: Data Access Objects –
design/pattern
• Purpose is to abstract your calls to the
database.
– Don't put SQL directly into your Java/JSP.
• You can change our database with minimal
affect on your code
• Identify bottle necks and bugs easier.
1/2

Intro:Importance of DAO
• Better design translates into easier to
understand code.
• Hibernate DAO - 3rd
party technology
– Benefits of common knowledge
– Fixes to technology
– Specialized for each database and optimized for
database access (caveats).
2/2

Intro:Comparison to SQL
• Problem with SQL
– never lived up to promise of standardization amongst
database vendors
– Uses Jdbc to access database – (no forced design)
– Is Relational
• With Hibernate:
– Caching
– Easier to code
– Standard access
– Is Object Oriented and maps to Relational.
1/2

Intro:Comparison to SQL
• Speed/performance
– Prepared Statements and caching (hib)
– Can batch process many DML statements. (hib)
– Better performance from PL/SQL (sql/hib)
• Maintenance/Updates (hib)
• Legacy system (depends)
– Using hibernate with legacy database systems
& Legacy java code retrofit with Hibernate
2/2

Configuration Hibernate/Java
• Download and install JDK 1.4 or 1.5
• Download version3 from
www.hibernate.org
• Setup Hibernate's Jars into your project's
classpath.
– The hibernate3.jar into your project's classpath;
and if need be all the <hib>/lib (if you don't
already have them).
1/5

Config:hibernate.properties
• Make sure that Oracle's client jdbc lib is in
your CLASSPATH
• Hibernate.properties needs to be in your
project's & runtime classpath.
HIBERNATE.PROPERTIES
#for OCI (local instance of Oracle, not using tnsnames.ora).
hibernate.dialect=org.hibernate.dialect.OracleDialect
hibernate.connection.driver_class=oracle.jdbc.driver.OracleDriver
hibernate.connection.username=joel
hibernate.connection.password=xyz
hibernate.connection.pool_size=5
hibernate.connection.url=jdbc:oracle:oci:@
hibernate.show_sql=true
2/5

Config: Download & Config
Xdoclet
[OPTIONAL]
• In order to run the "generation" of hibernate
XML you need to setup your classpath to include
Xdoclet libraries
• Download latest (v1.2.3) from
http://xdoclet.sourceforge.net/xdoclet/index.html
(www.xdoclet.org?)
– Download direct from
http://sourceforge.net/project/showfiles.php?group_id=31602
– Tag References
http://xdoclet.sourceforge.net/xdoclet/tags/hibernate-tags.html
3/5

config: Download & Config ANT
[OPTIONAL]
• In order to use ANT you'll need to setup your
PATH to include ANT. Check – run "ant"
• Download latest (v1.6.5) from http://ant.apache.org/
(www.ant.org?)
– Download direct from
http://www.axint.net/apache/ant/binaries/apache-ant-1.6.5-bin.zip
– Unzip and make sure "ant" is in your path. (right-click my computer ->
properties ->Advanced->Environmental Variables -> update PATH with directory
<ant_install>/bin)
4/5

config: Download & Config ANT
• SUMMARY:
– JDK [required]: PATH,CLASSPATH
– HIBERNATE [required]: CLASSPATH
• ORACLE or DBMS client [required]:
CLASSPATH (connection/lib info w/ hibernate.properties)
– XDOCLET [optional]:CLASSPATH
– ANT [optional]:CLASSPATH
5/5

Code & Fragments
• What we'll cover in the CODE section. For
each of the items below you'll see the XML,
the DDL SQL, Java code and an
explanation.
–Single Entity
–Primary Keys
–Many-to-One
–Many-to-Many
–DML (Query, Insert, Update, Delete)
–Extra topics

Code: Overview
• Hibernate layer is
independent of your
code
• Entities map via
hibernate XML
• Hibernate & you:
DML, caching,
isolation levels

Code[0]: Java POJO Entity
public class Person {
Long PERSON_ID=null; //manufactured surrogate key
String FIRST_NAME=null;
String LAST_NAME=null;
public Long getPERSON_ID(){…}
public void setPERSON_ID(String) {…}
public String getFIRST_NAME(){…}
public void setFIRST_NAME(String) {…}
public String getLAST_NAME(){…}
public void setLAST_NAME (String) {…}
}
See SAMPLE 0
1/4
Standard get/set &
need empty
constructor ~

Code[0]: XML for Entity

<?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="com.rhinosystemsinc.hibernate.samples_0.Person" table="SAMPLE0_Person" >
<id name="PERSON_ID" column="PERSON_ID" type="java.lang.Long" unsaved-value="null">
<generator class="hilo">
<param name="table">SAMPLE0_PERSON_SEQ</param>
<param name="column">NEXT</param>
</generator>
</id>
<property
name="FIRST_NAME"
type="java.lang.String"
update="true"
insert="true"
column="FIRST_NAME"
not-null="true"
unique="false"
length="100"
/>
<property name="LAST_NAME"/>
</class>
</hibernate-mapping>
2/4
<?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 name="PERSON_ID" column="PERSON_ID" type="java.lang.Long" unsaved-value="null">
<generator class="hilo">
<param name="table">SAMPLE0_PERSON_SEQ</param>
<param name="column">NEXT</param>
</generator>
</id>
Define the manufactured
surrogate primary key,
based on SEQUENCE.
Also natural composite
primary keys:
<composite-id>
<key-property
name="name"/>
<key-property
name="ssn"/>
</composite-id>
<property
name="FIRST_NAME"
update="true"
insert="true"
column="FIRST_NAME"
not-null="true"
unique="false"
length="100"
/>
<property name="LAST_NAME"/>

Code: Primary Keys
• All hibernate persisted Entity mappings
must have a primary key.
• Suggestion: Use surrogate generated keys.
– Hib supports natural keys ( & multi-column).
– Reason:
• Sometimes (rarely) keys will change values
• Easier to manage
3/4

Code[0]: Java Main Class
//SAVING A NEW OBJECT
org.hibernate.Session sess = sessFact.openSession(); //more on SessionFactory in a minute.
Person p = new Person();
p.setFIRST_NAME("John");
p.setLAST_NAME("Smith");
Transaction tx = sess.beginTransaction();
sess.saveOrUpdate(p);
tx.commit();
sess.close();
See SAMPLE 0
At this point, what if we do an
update, via SQLPLUS?
4/4

Code[0]: Java 1-to-Many
public class Person {
Long PERSON_ID=null; //manufactured surrogate key
String FIRST_NAME=null;
String LAST_NAME=null;
Set ADDRESSES=null;
public Set getADDRESSES()
{
return ADDRESSES;
}
public void setADDRESSES(Set ADDRESSES)
{
this.ADDRESSES = ADDRESSES;
}
…//rest of get/set methods
}
NEW

Code[0]: Person XML 1-to-Many
…
<hibernate-mapping>
<class name="com.rhinosystemsinc.hibernate.samples_0.Person" table="SAMPLE0_Person" >
…
<set
name="ADDRESSES"
lazy="false"
inverse="true"
cascade="save-update"
sort="unsorted"
outer-join="true">
<key column="PERSON_ID"/>
<one-to-many class="com.rhinosystemsinc.hibernate.samples_1.Address"/>
</set>
…
</class>
NEW
Any records that don't have address will be shown too.
all or save-update-delete
Notice one-to-many ~

Code[0]: Java 1-to-Many
public class Address {
Long ADDRESS_ID=null;
String STREET=null;
String APT_NO=null;
String CITY=null;
String STATE=null;
String ZIP=null;
Person person=null;// the person this address belongs to.
public Person getPerson()
{
return person;
}
public void setPerson(Person person)
{
this.person = person;
}
}
New Address class
Person reference ~
See Sample 1

Code[0]: Address XML 1-to-Many
…usual header
<class name="com.rhinosystemsinc.hibernate.samples_1.Address"
table="SAMPLE1_Address" dynamic-update="true">
<id name="ADDRESS_ID" column="ADDRESS_ID"
type="java.lang.Long" unsaved-value="null">
<generator class="sequence">
<param name="sequence">SAMPLE1_ADDRESS_SEQ</param>
<param name="parameters">INCREMENT BY 1 START WITH 1</param>
</generator>
</id>
<many-to-one name="person" class="com.rhinosystemsinc.hibernate.samples_1.Person"
cascade="save-update"
fetch="join"
lazy="false"
update="true"
insert="true"
column="PERSON_ID"
not-null="false"/>
…rest of properties defined
Address class
NOTICE different
definition sample of
the sequence
will always be
eagerly fetched.
~
For outer-join fetching or use 'select'
sequential select fetching. N+1 select prob.
Notice variable name in Address class
See Sample 1

Code[0]: main 1-to-Many
public static void main(String args[])
….
Address addr = new Address();
p.setLAST_NAME("Thompson");
p.setADDRESSES(new HashSet());
p.getADDRESSES().add(addr);
p.setCreated(new Date());
addr.setSTREET("12345 Easy");
addr.setCITY("Sacramento");
addr.setSTATE("CA");
addr.setORDER_POS(new Long(1));
addr.setCreated(new Date());
addr.setPerson(p);
…
sess.save(p);
tx.commit();
…
…
See Sample 1
assign person reference to address ~
Create an empty "set" and assign to Person
Add the address to the "set"

Code[0]: Java Many-to-Many
…same as before
Set persons=null;// the person this address belongs to.
public Set getPersons()
{
return persons;
}
public void setPersons(Set persons)
{
this.persons = persons;
}
}
NEW ~
See Sample 2

Code[0]: XML Many-to-Many
…usual header
<class name=...Address>
<set name="persons"
table="SAMPLE2_PERSON_ADDRESS">
<key column="ADDRESS_ID"/>
<many-to-many
class="com.rhinosystemsinc.hibernate.samples_2.Person"
column="PERSON_ID"/>
</set>
…rest of properties defined
</class>
"Set persons=null" in java
See Sample 1
Intermediate M-M table
M-M definition,
referencing the Person
class by PERSON_ID
~

Code[0]: Main Many-to-Many
p.setLAST_NAME("Thompson");
p.setCreated(new Date());
…
//revised! for many-to-many
addr.setPersons(new HashSet());
addr.getPersons().add(p);
//ADD NEW PERSON TO ADDRESS
Person p2=new Person();
p2.setFIRST_NAME("Martha");
p2.setLAST_NAME("Thompson");
p2.setADDRESSES(new HashSet());
p2.getADDRESSES().add(addr);
addr.getPersons().add(p2);
See Sample 1
Create empty list of Addresses
Martha also lives at the SAME address,
here we add the address to the p2 object ~
Setup empty Address and Person object

Code[0]: Reference Data
• Data that doesn't change usually loaded at system
installation time. (Use 2nd
level Cache).
– Examples: STATES, CATEGORY, ZIP..etc.
• Strategy
– Setup XML class with element cache as read-only
– Setup cache for relation as read-only
– Call a method to load All read-only objects at
initialization (actually even everytime).
(for example…)

…
<class name="com.rhinosystemsinc.sample.Event">
…
<many-to-one
name="CATEGORY"
class="com.rhinosystemsinc.sample.Category"
cascade="none"
update="false"
insert="false"
column="CATEGORY_ID"
not-null="true" />
</class>
For the EVENT class
which operations should be cascaded from
the parent object to the associated object
Variable name for java class
Category CATEGORY=null;
We will not update or insert from this relationship. ~

…
<class name="com.rhinosystemsinc.sample.Category" mutable="false">
<cache usage="read-only" />
…
</class>
----------------------------------------------------------------------------------------------------------
In your Java code, load the objects at least once…
…
org.hibernate.Query q = sess.createQuery("from Category");
q.setCacheMode(org.hibernate.CacheMode.NORMAL);
q.setCacheable(true);
java.util.List result = q.list();
…
For the CATEGORY class
Set cache to be read-only
Also - notice no need for a reference back to Event class
Make sure your Query sets up the CACHING! (2nd
level) ~

Code: Components
• Components
"Fine-grained object Model" - more Classes than Tables
– Value Type – not Entity reference
• Meaning, you want separate Java class (from the main entity)
for this property, and yet it is stored in DB with main entity
• Lets Consider ZIP_CODE as example.
• Address w/ ZipCode attribute
• ZipCode defines ZIP_CODE and ZIP_4DIGIT_CODE as fields
• Address Table has two fields in table (w/ same field names).

Code: Component (example)
//JAVA ADDRESS CLASS:
…
ZipCode ZIP=null;
public ZipCode getZIP(){…}
public void setZIP(ZipCode ZIP)
}
//Address.hbm.xml ------------------------------------------------------------------------------------------
…usual header
<class name="com.rhinosystemsinc.hibernate.samples_3.Address"
table="SAMPLE3_Address" dynamic-update="true">
…
<component name="ZIP" class="com.rhinosystemsinc.hibernate.samples_3.ZipCode">
…
</class>
ZipCode variable, name is same as
mapping below.
Notice use of "component", with class
name ~
<component name="ZIP" class="com.rhinosystemsinc.hibernate.samples_3.ZipCode">

//Java ZipCode Class
public class ZipCode {
// Components have NO ID...they are just entirely dependent on
// containing Entity - in this case Address - in otherwords,
// we want a Java Class representation of ZipCode, but want it
// mapped into the Address table with ZIP_CODE and ZIP_4DIGIT_CODE
// as attributes of Address table.
String ZIP_CODE = "";
String ZIP_4DIGIT_CODE = "";
public String getZIP_4DIGIT_CODE(){…}
public void setZIP_4DIGIT_CODE(String ZIP_4DIGIT_CODE){…}
public String getZIP_CODE(){…}
public void setZIP_CODE(String ZIP_CODE){…}
}
NO ID
In this example: Attribute names map directly to database column names ~
Two attributes
w/
getters/setters

//SQL for Address table:
create table SAMPLE3_Address
(
ADDRESS_ID number primary key,
STREET varchar2(512),
APT_NO varchar2(64),
CITY varchar2(512),
STATE varchar2(2),
ZIP_CODE varchar2(5),
ZIP_4DIGIT_CODE varchar2(4)
);
Notice same name as
ZipCode variables. ~

//Java Main Code
…
ZipCode zip=new ZipCode();
zip.setZIP_CODE("95603");
zip.setZIP_4DIGIT_CODE("4456");
addr.setZIP(zip);
addr.setPersons(new HashSet());
addr.getPersons().add(p);
…
sess.saveOrUpdate(p);
Usual initialization here.
Create a ZipCode
object, initialize it, and
set to the Address
Note: query returns an Address object w/
ZipCode filled in automatically. ~

Code: Querying
• Hibernate offers a variety of ways to query
the objects:
– SQL – straight SQL (parsed SQL 92 standard)
– HQL – hibernate's query language (SQL based)
– QBE – query by example
– Criteria Queries – Object oriented

Code: Querying
• HQL simple example:
Query q = sess.createQuery("from Person");
// ALSO
Query q = sess.createQuery("from Person p where " +
"p.FIRST_NAME = :fname and " +
"p.LAST_NAME =:lname");
q.setString("fname", First); //can also use positional parameters
q.setString("lname", Last);
See all examples for quering
Can also use ? As positional param
Then use:
q.setString(0, First);
q.setString(1, Last);
Use the session to create the Query
object.
Returns a list, that you can iterate
through and cast the "objects" to
Person. ~

Code: Querying
• HQL scalar example (from reference.pdf):
Iterator results = sess.createQuery(
"select cat.color, min(cat.birthdate),
count(cat) from Cat cat " +
"group by cat.color").list().iterator();
while ( results.hasNext() )
{
Object[] column = (Object[]) results.next();
Color type = (Color) column[0];
Date oldest = (Date) column[1];
Integer count = (Integer) column[2];
.....
}
Notice alias "cat" lowercase
Notice cast – same as attribute
declared in Cat class ~

Code: SQL Querying
• SQL example:
org.hibernate.SQLQuery q = sess.createSQLQuery("select *
" +
"
from SAMPLE0_PERSON" +
"
where " +
"
FIRST_NAME = :fname " +
"
and LAST_NAME = :lname");
q.addEntity(Person.class);
q.setString("fname", First); //can also use
positional parameters
…
createSQLQuery
Tell hibernate about actual
class
Bind parameters ~

Code: SQL Querying
• SQL example #2:
org.hibernate.SQLQuery q = sess.createSQLQuery("select
{Person.*} " +
"
from SAMPLE0_PERSON Person where " +
"
Person.FIRST_NAME = :fname " +
"
and Person.LAST_NAME =:lname");
q.addEntity("Person",Person.class);
q.setString("fname", First); //can also use
positional parameters
…See all examples for quering
See also:
q.addScalar(String columnAlias, Type type).
q.addJoin(String alias, String path). Where path is the
path to the java collection member variable name of the
parent class. In our example it would be
"Person.ADDRESSES" ~
With AliasWith AliasWith Alias

Pros/Cons
• Cons
– Lots of idiosyncrasies. – caching, flushing,
inverse…etc. (But can configure/disable them.)
– Learning curve is fairly steep.
(learn a way and stick with it).
– Not good for bulk-inserts (batch processing)
(forced to use PL/SQL within hibernate or jdbc)
– Java-XML-table all defining entity (good and
bad) – (xdoclet and other tools – setup system of generating base/core
code elements – use patterns and conventions)

Pros/Cons
• Pros
– Simple to understand concepts.
– Stick with tools and frameworks, then can speed up
development time.
– Caching for you – so better performance.
(if you don’t use cache, then similar to straight SQL w/ preparedstatement
performance).
– Highly extensible and customizable to suite your needs
for new development and conversion.
– Defacto standard, via OpenSource LGPL license, non
proprietary, and known by developer community
(cost, maintenance, bugs..etc.)

Resources
• Hibernate.org – is the best most up-to-date
– FAQs : http://www.hibernate.org/5.html
• Advanced Problems, Tips and Tricks, Performance and more…
• Evaluation- http://www.hibernate.org/263.html
– Doc link: http://www.hibernate.org/5.html
– Migration (A MUST!) – http://www.hibernate.org/250.html
• Package change: net.sf -> org.hibernate
• SessionFactory
• Criteria Query

Resources
• Hibernate installation
– <installdir>/doc/
{api,other,reference}/en/pdf/hibernate_reference.pdf (great for
reference, yet not sufficient for beginners to "learn").
– <installdir>/eg – samples

Resources
• Miscellaneous
– Book: Hibernate In Action http://www.manning.com/bauer
– Performance #'s:
http://www.sourcelabs.com/?sidemenu=3&page=software&sub=sash_hibernateperftest
• Hibernate user FORUM - http://forum.hibernate.org/
(+200 msg/day)
• CaveatEmptor Sample from Hibernate:
http://caveatemptor.hibernate.org/

End 0f Presentation
Thank you!
• Extra topics session follow, if time.
~ Or ~
• Q & A
• Future Questions:
email: joel@rhinosystemsinc.com

XDoclet
• XDoclet is used to generate hibernate XML
files.
– You specify annotation tags in your Java code
– Run an xdoclet-ANT task on the java code
– Make sure xml is in your classpath (the
xdoclet-ant will put in src directory)
• Hibernate Annotations, next step.
See all examples of Xdoclet in the java code

XDoclet example
•Person.java
Long PERSON_ID=null;
String FNAME=null;
/** @hibernate.id
* unsaved-value="null"
* generator-
class="sequence"*/
public Long getPERSON_ID(){}
public void
setPERSON_ID(Long){}
/** @hibernate.property */
public String getFNAME()
{}
public void
setFNAME(String){}
See all examples for xdoclet
• Person.hbm.xml
<id name="PERSON_ID"
column="PERSON_ID"
type="java.lang.Long"
unsaved-value="null">
<!– …some xdoclet
commentary…-->
</generator>
</id>
<property
name="LAST_NAME"
update="true"
insert="true"
column="LAST_NAME"
/>
Xdoclet Ant
task/** @hibernate.id
* unsaved-
value="null"
* generator-
class="sequence"*/
public
Long get
/** @hibernate.property */
<id name="PERSON_ID"
column="PERSON_ID"
type="java.lang.Long"
unsaved-value="null">
<!– …some xdoclet
commentary…-->
</generator>
</id><property
name="LAST_NAME"
update="true"
insert="true"
column="LAST_NAME"
/>
•Maintain tags in one location - Java
•On building (one click) create hbm.xml files

Topics Not Covered
• SessionFactory
• PLSQL
• Custom UserType
• Caching (1st
& 2nd
Level)
• Transactions and
Isolation Levels
– JDBC trx semantics
– Concurrent Updates and
versioning.
• Session and Flushing
– Session "unit of work"
• Interceptors & Logging
• Definitions:
– Transient, Persistent,
Detached
• Subclass

Hibernate java and_oracle

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