Copyright 2006, rhinosystemsinc.com all rights reserved HIBERNATE/Java & ORACLE Overview of...

copyright 2006, rhinosystemsinc.com all rights reserved

HIBERNATE/Java & ORACLE

Overview of technology for Hibernate 3

as of 1/2006

By Joel A. Thompson ([email protected])

Goal: Present Hibernate to first time users, and get you

started with all the major concepts right away.


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.html3/5


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

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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>


NEWAny 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;

}…//rest of get/set methods

}

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(); Person p = new Person(); p.setFIRST_NAME("John"); 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 beforeSet persons=null;// the person this address belongs to.

public Set getPersons()

{

return persons;

}

public void setPersons(Set persons)

{

this.persons = persons;

}

…//rest of get/set methods

}

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-ManyAddress addr = new Address();

Person p = new Person();

p.setFIRST_NAME("John");

p.setLAST_NAME("Thompson");

p.setADDRESSES(new HashSet());

p.getADDRESSES().add(addr);

p.setCreated(new Date());

addr.setSTREET("12345 Easy");

…

//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 classCategory 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 CodeAddress addr = new Address();Person p = new Person(); p.setFIRST_NAME("John");p.setADDRESSES(new HashSet());p.getADDRESSES().add(addr);addr.setSTREET("12345 Easy");…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 paramThen 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);




…See all examples for quering

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);




…


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 Alias With Alias With 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: [email protected]


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.javaLong 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">

<generator class="sequence">

<!– …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">

<generator class="sequence">

<!– …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

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