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IRMIS rdbCore Java API
Object-Relational Modelling (ORM)
Argonne National Laboratory
A U.S. Department of Energy
Office of Science Laboratory
Office of Science
U.S. Department of Energy Operated by The University of Chicago
IRMIS rdbCore Java API
• What is rdbCore?
- Database schema definition (ddl)
- Static for now, but possible to generate for multiple db
- Process variable crawler
- Java database access layer (also PHP)
• Source code tree overview
irmis/
apps/ -> pv viewer, component viewer/editor, etc.
rdbCore/ -> rdbCore.jar
ddl/
crawler/perl/
db/
php/
java/
gov/anl/aps/irmis/persistence/pv
2
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Object-Relational Mapping (ORM)
- Bridges gap between relational data model and object-oriented
data model of applications
- This “gap” responsible for a significant amount of development
and maintenance hours
- ORM allows focus on application and data, not transforming
between the two models
• Java ORM <==> Hibernate (Gavin King)
- LGPL license
- Development began in 2001
- Joined jboss.org in 2003, so commercial support and training
available
- Very popular, mature, with active support forums
- Excellent book “Hibernate in Action” (2005 - Bauer, King)
3
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Data Objects
- IOC Record
- IOCBoot RecordType
- IOCResource Field
- URI FieldType
• Data Access Objects
- IOCBootDAO
- IOCBoot findByIocName(String iocName)
- List findCurrentLoads()
- RecordDAO
- setRecordTypeConstraint(List recTypes)
- setRecordNameGlobConstraint(String recNamePattern)
- List findByConstraints() 4
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Code example
// retrieve set of current ioc boot instances, and all their process variables
IOCBootDAO ibDAO = new IOCBootDAO();
List bootList = null;
Try {
bootList = ibDAO.findCurrentLoads();
} catch (DAOException de) {
// handle exception
}
// iterate over the results
Iterator bootIt = bootList.iterator();
while (bootIt.hasNext()) {
IOCBoot iocBoot = (IOCBoot)bootIt.next();
String iocName = iocBoot.getIoc().getIocName();
List resources = iocBoot.getIocResources(); // eager fetch, so data already here
List records = iocBoot.getRecords(); // lazy, so addtl. query issued here
}
5
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• How is this done with Hibernate?
- Design the object model and relational schema (what order?)
- Depends on whether rdbms schema came first or not
- APS designed rdbms schema with application in mind, so our
object model entities are almost 1-to-1 with relational entities
(hibernate still a big plus).
- Hibernate can auto-generate class source code and/or ddl if
desired
- APS manually created classes and ddl (for now)
6
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Hibernate revolves around Session class
hibernate.cfg.xml
Record.hbm.xml
Field.hbm.xml
Session session = sessionFactory.openSession()
IOCBoot.hbm.xml
hibernate.cfg.xml
<hibernate-configuration>
<session-factory>
<property name=“connection.*” value=“blah”/>
<property name=“dialect” value=“net.sf.hibernate.dialect.MySQLDialect” />
<mapping resource=“gov/anl/aps/irmis/persistence/pv/Record.hbm.xml” />
<mapping resource=“gov/anl/aps.irmis/persistence/pv/Field.hbm.xml” />
<mapping resource=“gov/anl/aps/irmis/persistence/pv/IOCBoot.hbm.xml” />
</session-factory>
</hibernate-configuration>
7
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Partial Record.hbm.xml mapping
<hibernate-mapping>
<class name=“gov.anl.aps.irmis.persistence.pv.Record”
table=“rec” lazy=“true” >
<id name=“id” column=“rec_id” type=“long” >
<generator class=“native”/>
</id>
<property name=“recordName” type=“string” column=“rec_nm” />
<set name=“fields” inverse=“true” lazy=“true” >
<key column=“rec_id” />
<one-to-many class=“gov.anl.aps.irmis.persistence.pv.Field” />
</set>
<many-to-one name=“recordType” column=“rec_type_id”
class=“gov.anl.aps.irmis.persistence.pv.RecordType” />
</class>
</hibernate-mapping>
8
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Record class (Record.java)
Public class Record implements Serializable {
private Long id; public boolean equals (Object o) {
private String recordName; if (this == other) return true;
private Set fields = new HashSet(); if (!(other instanceof Record))
private RecordType recordType; return false;
// constructor and accessor methods final Record castO = (Record)o;
public Record() {} return this.getIocBoot().getId()==castO
public Long getId() { return this.id; } .getIocBoot().getId() && this.getRecordName()
public void setId(Long id) { this.id = id; } ==castO.getRecordName();
public Set getFields() { return this.fields; } }
public void setFields(Set fields) { public int hashCode() {
this.fields = fields; int result = HashCodeUtil.SEED;
} result = HashCodeUtil.hash(result, getIocBoot().getId());
public void addField(Field field) { result = HashCodeUtil.hash(result, getRecordName());
field.setRecord(this); return result;
fields.add(field); }
} }
9
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Querying for objects using HQL (Hibernate Query Language)
- What is HQL?
- minimal OO extension to SQL select
- Why?
- Query in terms of objects you are interested in
- Db independence since Hibernate generates SQL for your db
- Optimization - hibernate generally makes optimal SQL
List records = session.find(“select from Record r where r.recordName like „ABC%‟”);
List records = session.find(“from Record r join fetch r.fields”);
IOCBoot boot = session.find(“from IOCBoot ib where ib.ioc.iocName = „iocpar01‟”);
- OR - if you absolutely have to use native SQL and JDBC
Connection con = session.connection();
// any JDBC stuff can be done here
10
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Saving or updating new objects
Record rec = new Record();
rec.setRecordName(“AB:CD:ai”);
// set remaining fields except id
Transaction tx = session.beginTransaction();
session.saveOrUpdate(rec);
tx.commit();
11
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
IRMIS rdbCore Java API
• Hibernate experience
- It has a learning curve (2 weeks ?)
- Very active support forums where core developers lurk and
answer questions within hours
- Extremely flexible
- Only a small corner of mapping possibilities shown
- Will work with schemas using natural keys
- Objects can be mapped to one or many tables, either through
composition or association
- Easy to tweak mappings and watch behavior of SQL
(comparing query time using lazy versus eager fetch)
- Good log output (uses commons-logging and log4j)
12
Pioneering Office of Science
Science and U.S. Department
Technology of Energy
