Cayenne, OpenJPA, iBatis Apache Persistence Layers ApacheCon EU 2008 Henning Schmiedehausen [email_address]

The O/R impedance mismatch Objects (Java Knowledge) RDBMS ?

In a nutshell… “ Object-Relational mapping (O/RM), is a programming technique that links databases to object-oriented language concepts, creating (in effect) a ‘virtual object database’.” – Wikipedia

“ Object-Relational mapping (O/RM),

is a programming technique that links

databases to object-oriented language

concepts, creating (in effect) a ‘virtual

object database’.”

– Wikipedia

Selection criterias Data access (CRUD) Developers knowledge Database languages (SQL, DDL)

Data access (CRUD)

Developers knowledge

Database languages (SQL, DDL)

Can we stop here? I just need to query data for my (web) application. I could use the “industry standard”, right?

Yeah, right JDO 1.0, 2.0, 2.1 ? EJB 2 (Ieek!) or 3 ? JPA ? J2SE ? J2EE ? And wait, there is more… … Legacy code? Optimized SQL? … Transparent or explicit persistence?

JDO 1.0, 2.0, 2.1 ?

EJB 2 (Ieek!) or 3 ?

JPA ?

J2SE ? J2EE ?

And wait, there is more…

… Legacy code? Optimized SQL?

… Transparent or explicit persistence?

Meanwhile, outside Apache… Hibernate „ de facto standard“ (L)GPL licensed driven by a single company TopLink Essentials JSR 220 Reference Implementation CDDL + GPLv2 driven by a single company

Hibernate

„ de facto standard“

(L)GPL licensed

driven by a single company

TopLink Essentials

JSR 220 Reference Implementation

CDDL + GPLv2

driven by a single company

Ok, ok, ok… So, why Apache?

Because we are at ApacheCon…

Apache Software License V2 Open Source Commercial friendly Non discriminatory

Apache Software License V2

Open Source

Commercial friendly

Non discriminatory

Strong community Many contributors Meritocracy Commercial support available

Strong community

Many contributors

Meritocracy

Commercial support available

Apache Persistence Layers Apache Cayenne Apache OpenJPA Apache iBatis not in this talk: Apache Torque (http://db.apache.org/torque/) Apache OJB (http://db.apache.org/ojb/)

Apache Cayenne

Apache OpenJPA

Apache iBatis

not in this talk:

Apache Torque (http://db.apache.org/torque/)

Apache OJB (http://db.apache.org/ojb/)

Common Ground JDBC, JTA, JNDI Many popular DBs supported: MySQL, PostgreSQL, Oracle, HSQLDB, Apache Derby XML mapping definition files 1:1, 1:n, m:n mappings native and generated primary keys

JDBC, JTA, JNDI

Many popular DBs supported:

MySQL, PostgreSQL, Oracle, HSQLDB, Apache Derby

XML mapping definition files

1:1, 1:n, m:n mappings

native and generated primary keys

Where are we? Apache Cayenne 2.0.4 (Oct 12th, 2007) 3.0M3 Apache OpenJPA 1.0.2 (Feb 18th, 2008) 1.1.0-SNAPSHOT Apache iBatis 2.3.1 Beta (Mar 25th, 2008) 3.0 in planning state

Apache Cayenne

2.0.4 (Oct 12th, 2007)

3.0M3

Apache OpenJPA

1.0.2 (Feb 18th, 2008)

1.1.0-SNAPSHOT

Apache iBatis

2.3.1 Beta (Mar 25th, 2008)

3.0 in planning state

Swing GUI tool for modeling Ant support, maven through ant tasks concepts related to WebObjects EOF

Swing GUI tool for modeling

Ant support, maven through ant tasks

concepts related to WebObjects EOF

Cayenne Pros: GUI modeler included Good documentation Cons: all data objects inherit DataObject (3.0 will have POJO support) no standards compliant API (3.0 will be JPA compliant)

Pros:

GUI modeler included

Good documentation

Cons:

all data objects inherit DataObject (3.0 will have POJO support)

no standards compliant API (3.0 will be JPA compliant)

implements JPA (JSR-220) Ant support, maven through ant tasks Command line tools included based on Kodo, donated by BEA

implements JPA (JSR-220)

Ant support, maven through ant tasks

Command line tools included

based on Kodo, donated by BEA

Pros: Standards based (JPA) POJO support Good documentation Cons: Some learning effort required Only command line tools included

Pros:

Standards based (JPA)

POJO support

Good documentation

Cons:

Some learning effort required

Only command line tools included

Example code This talk can only scratch the concepts Example code is available from my homepage, along with examples for other O/R tools: http://henning.schmiedehausen.org/or-mappers/ http://svn.softwareforge.de/svn/opensource/talks/or-mappers/

This talk can only scratch the concepts

Example code is available from my homepage, along with examples for other O/R tools:

http://henning.schmiedehausen.org/or-mappers/

http://svn.softwareforge.de/svn/opensource/talks/or-mappers/

A sample relation

Cayenne property class People extends CayenneDataObject { void setFirstName(String firstName ) { writeProperty ( "firstName" , firstName ); } String getFirstName() { return (String) readProperty ( "firstName" ); }

class People extends CayenneDataObject {

void setFirstName(String firstName ) { writeProperty ( "firstName" , firstName );

}

String getFirstName() { return (String) readProperty ( "firstName" );

}

Cayenne relation class People extends CayenneDataObject { void addToContacts(Contact contact ) { addToManyTarget ( "contacts" , contact , true); } void removeFromContacts(Contact contact ) { removeToManyTarget ( "contacts" , contact , true); } List getContacts() { return (List) readProperty ( "contacts" ); }

class People extends CayenneDataObject {

void addToContacts(Contact contact ) { addToManyTarget ( "contacts" , contact , true);

}

void removeFromContacts(Contact contact ) { removeToManyTarget ( "contacts" , contact , true);

}

List getContacts() { return (List) readProperty ( "contacts" );

}

Cayenne mapping <obj-entity name=&quot;People&quot; className=&quot; om.People &quot; dbEntityName=&quot; people &quot;> <obj-attribute name=&quot; firstName &quot; type=&quot;java.lang.String&quot; db-attribute-path=&quot; people_firstname &quot;/> </obj-entity> <obj-relationship name=&quot;people&quot; source=&quot; Contact &quot; target=&quot; People &quot; db-relationship-path=&quot;people&quot;/> Class/DB Map Prop. / Col Map Obj Relation

<obj-entity name=&quot;People&quot; className=&quot; om.People &quot; dbEntityName=&quot; people &quot;>

<obj-attribute name=&quot; firstName &quot; type=&quot;java.lang.String&quot; db-attribute-path=&quot; people_firstname &quot;/>

</obj-entity>

<obj-relationship name=&quot;people&quot; source=&quot; Contact &quot; target=&quot; People &quot; db-relationship-path=&quot;people&quot;/>

OpenJPA property @Entity @Table(name=&quot;people&quot;) public class People { private String firstName ; @Basic @Column(name=&quot;people_firstname&quot;) public String getFirstName() { return firstName ; } public void setFirstName(String firstName) { this. firstName = firstName; } Class/DB Map Prop. / Col Map

@Entity @Table(name=&quot;people&quot;)

public class People {

private String firstName ;

@Basic @Column(name=&quot;people_firstname&quot;)

public String getFirstName() {

return firstName ;

}

public void setFirstName(String firstName) {

this. firstName = firstName;

}

OpenJPA relation @Entity @Table(name=&quot;people&quot;) public class People { private Collection<Contact> contacts ; @OneToMany(mappedBy = &quot;people&quot;, cascade={CascadeType.PERSIST, CascadeType.REMOVE}) public Collection<Contact> getContacts() { return contacts ; } public void setContacts( Collection<Contact> contacts) { this. contacts = contacts; } Class/DB Map Obj Relation

@Entity @Table(name=&quot;people&quot;)

public class People {

private Collection<Contact> contacts ;

@OneToMany(mappedBy = &quot;people&quot;, cascade={CascadeType.PERSIST, CascadeType.REMOVE})

public Collection<Contact> getContacts() {

return contacts ;

}

public void setContacts( Collection<Contact> contacts) {

this. contacts = contacts;

}

Accessing the Mapper Cayenne: DataContext dataContext = DataContext.createDataContext(); OpenJPA: EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory(); EntityManager em = entityManagerFactory .createEntityManager();

Cayenne:

DataContext dataContext = DataContext.createDataContext();

OpenJPA:

EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory();

EntityManager em = entityManagerFactory .createEntityManager();

Retrieving an Object by PK Cayenne: People user = (People) DataObjectUtils .objectForPK( dataContext , People.class, 2); OpenJPA: People user = (People) em .find(People.class, 2L);

Cayenne:

People user = (People) DataObjectUtils .objectForPK( dataContext , People.class, 2);

OpenJPA:

People user = (People) em .find(People.class, 2L);

Changing an Object Cayenne: People people = retrieve(); people.setMember(true); dataContext. commitChanges() ; OpenJPA: Transaction tx = em .getTransaction(); tx.begin() ; People people = retrieve(); people.setMember(true); tx.commit() ;

Cayenne:

People people = retrieve();

people.setMember(true);

dataContext. commitChanges() ;

OpenJPA:

Transaction tx = em .getTransaction();

tx.begin() ;

People people = retrieve();

people.setMember(true);

tx.commit() ;

And Now… …for Something Completely Different

iBATIS Data mapper framework couples SQL queries to Java objects Ant support, maven through ant tasks Abator tool / Eclipse plugin

Data mapper framework

couples SQL queries to Java objects

Ant support, maven through ant tasks

Abator tool / Eclipse plugin

iBATIS Pro: fast, lightweight, unintrusive Other Languages: Ruby, .NET POJO support Eclipse plugin Cons: SQL knowledge required „ not mainstream“ concept

Pro:

fast, lightweight, unintrusive

Other Languages: Ruby, .NET

POJO support

Eclipse plugin

Cons:

SQL knowledge required

„ not mainstream“ concept

A mapped query <select id=&quot; getPeople &quot; parameterClass=&quot;people&quot; resultMap=&quot;peopleResult&quot; > select * from people <dynamic prepend=&quot;where&quot;> <isNotNull prepend=&quot;and&quot; property=&quot;id&quot;> people_id = #id# </isNotNull> </dynamic> </select>

<select id=&quot; getPeople &quot; parameterClass=&quot;people&quot;

resultMap=&quot;peopleResult&quot; >

select * from people

<dynamic prepend=&quot;where&quot;>

<isNotNull prepend=&quot;and&quot; property=&quot;id&quot;>

people_id = #id#

</isNotNull>

</dynamic>

</select>

Query examples Querying a single object People select = new People (); select.setId(2L); People user = (People) sqlMap .queryForObject(&quot; getPeople &quot;, select); Querying a list List select = sqlMap .queryForList(&quot; getPeople &quot;, null);

Querying a single object

People select = new People ();

select.setId(2L);

People user = (People) sqlMap .queryForObject(&quot; getPeople &quot;, select);

Querying a list

List select = sqlMap .queryForList(&quot; getPeople &quot;, null);

Caveat iBatis is not an O/R mapper, it is a data mapper! calling retrieve() twice returns: Cayenne, OpenJPA: The same object iBatis: Two different objects

iBatis is not an O/R mapper, it is a data mapper!

calling retrieve() twice returns:

Cayenne, OpenJPA: The same object

iBatis: Two different objects

Which one to use? This table is highly subjective! YMMV! … when standards compliance is a concern OpenJPA … if you need J2EE integration All of them … if your SQL is better than your Java / .NET iBATIS … if your Java is better than your SQL Cayenne, OpenJPA When What

This table is highly subjective! YMMV!

Where to go from here? http://henning.schmiedehausen.org/or-mappers/ Talk slides and Example code O/R Mappers Homepages: http://cayenne.apache.org/ http://openjpa.apache.org/ http://ibatis.apache.org/ Other ASF persistence mappers: http://db.apache.org/torque / http://db.apache.org/ojb /

http://henning.schmiedehausen.org/or-mappers/

Talk slides and Example code

O/R Mappers Homepages:

http://cayenne.apache.org/

http://openjpa.apache.org/

http://ibatis.apache.org/

Other ASF persistence mappers:

http://db.apache.org/torque /

http://db.apache.org/ojb /

?

Thanks for your attention!