Download - IRMIS rdbCore Java API

A U.S. Department of EnergyOffice of Science LaboratoryOperated by The University of Chicago

Argonne National Laboratory

Office of ScienceU.S. Department of Energy

IRMIS rdbCore Java API

Object-Relational Modelling (ORM)

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Pioneering Science andTechnology

Office of Science U.S. Department

of Energy


• 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

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• 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)

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• 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()

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• 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

}

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• 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)

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• Hibernate revolves around Session class

Session session = sessionFactory.openSession()

hibernate.cfg.xml

IOCBoot.hbm.xml

Field.hbm.xml

Record.hbm.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>

hibernate.cfg.xml

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• 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>

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• Record class (Record.java)Public class Record implements Serializable {

private Long id;

private String recordName;

private Set fields = new HashSet();

private RecordType recordType;

// constructor and accessor methods

public Record() {}

public Long getId() { return this.id; }

public void setId(Long id) { this.id = id; }

public Set getFields() { return this.fields; }

public void setFields(Set fields) {

this.fields = fields;

}

public void addField(Field field) {

field.setRecord(this);

fields.add(field);

}

public boolean equals (Object o) {

if (this == other) return true;

if (!(other instanceof Record))

return false;

final Record castO = (Record)o;

return this.getIocBoot().getId()==castO

.getIocBoot().getId() && this.getRecordName()

==castO.getRecordName();

}

public int hashCode() {

int result = HashCodeUtil.SEED;

result = HashCodeUtil.hash(result, getIocBoot().getId());

result = HashCodeUtil.hash(result, getRecordName());

return result;

}

}

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• 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

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• 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();

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• 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)