A U.S. Department of Energy Office of Science Laboratory Operated by The University of Chicago Argonne National Laboratory Office of Science U.S. Department of Energy IRMIS rdbCore Java API Object-Relational Modelling (ORM)

Pioneering Science and Technology Office of Science U.S. Department of Energy 2 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

Pioneering Science and Technology Office of Science U.S. Department of Energy 3 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 Joined jboss.org in 2003, so commercial support and training available -Very popular, mature, with active support forums -Excellent book “Hibernate in Action” ( Bauer, King)

Pioneering Science and Technology Office of Science U.S. Department of Energy 4 IRMIS rdbCore Java API Data Objects -IOCRecord -IOCBootRecordType -IOCResourceField -URIFieldType Data Access Objects -IOCBootDAO - IOCBoot findByIocName(String iocName) - List findCurrentLoads() -RecordDAO - setRecordTypeConstraint(List recTypes) - setRecordNameGlobConstraint(String recNamePattern) - List findByConstraints()

Pioneering Science and Technology Office of Science U.S. Department of Energy 5 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 }

Pioneering Science and Technology Office of Science U.S. Department of Energy 6 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)

Pioneering Science and Technology Office of Science U.S. Department of Energy 7 IRMIS rdbCore Java API Hibernate revolves around Session class Session session = sessionFactory.openSession() hibernate.cfg.xml IOCBoot.hbm.xml Field.hbm.xml Record.hbm.xml hibernate.cfg.xml

Pioneering Science and Technology Office of Science U.S. Department of Energy 8 IRMIS rdbCore Java API Partial Record.hbm.xml mapping <class name=“gov.anl.aps.irmis.persistence.pv.Record” table=“rec” lazy=“true” > <many-to-one name=“recordType” column=“rec_type_id” class=“gov.anl.aps.irmis.persistence.pv.RecordType” />

Pioneering Science and Technology Office of Science U.S. Department of Energy 9 IRMIS rdbCore Java API 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; }

Pioneering Science and Technology Office of Science U.S. Department of Energy 10 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

Pioneering Science and Technology Office of Science U.S. Department of Energy 11 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();

Pioneering Science and Technology Office of Science U.S. Department of Energy 12 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)