[Dolenc] Hibernate vs. iBatis

HIBERNATE VS. IBATIS OR TWO WAYS OF DATABASE ACCESS BOŠTJAN DOLENC, MARAND INŽENIRING

WHAT WE'RE ABOUT TO SEE: • A bit about relevancy • The ORM way (with Hibernate examples) • The JDBC+ way (with iBatis examples) • Problems • Crossing the chasm • Discussion (time permitting)

RELEVANCY • Data matters more than code • JDBC sucks – Aimde at system development – Lacks higher level features: statement manipulation, encapsulation, caching – Cumbersome use • Objects ≠ Relations (holy war)

ORM WAY • Object/class centric approach • Strict Object-Relational Mapping or “I hate bloody SQL” • Using Hibernate 3.x (and JDK <1.5)

ORM EXAMPLE

ORM EXAMPLE - CONTINUED

JDBC+ WAY • SQL centric approach • Improved JDBC or “Ad-hoc queries without JDBC horrors”

JDBC+ EXAMPLE

JDBC+ EXAMPLE - CONTINUED

ORM PROBLEM: 1+N FETCHING 1 2 10 1 11 1 42 10 12 1 43 11 13 2 44 11 22 42 45 12 23 42 46 13 ... ...

ORM PROBLEM: 1+N FETCHING - CONTINUED • Eager loading to the rescue: – Next-level-only fails in deep hierarchies – All-levels fails when accessing only top-level • HQL to the rescue: – from Customer c join c.contracts co join co.bundles b join b.services s

ORM PROBLEM: MASSIVE UPDATES for (ServiceTimeline st : services) { if (st.getValidTo() == null) 1 1.1. { st.setValidTo(newDate); 2 1.2. 1.12. } 3 15.10. } 4 1.2. 5 1.1 1.12. update service_timeline set valid_to = #newDate# where valid_to is null

OTHER ORM PROBLEMS: • xQL (HQL, JP QL) ≠ SQL – Tools – Limited to programmers • POJOs sometimes aren’t Plain and Old – Common base class, proxies, code generation, annotations... – Build/startup overhead, subtle reflection bugs

JDBC+ PROBLEM: LOTS OF WORK FOR SIMPLE THINGS

JDBC+ PROBLEM: LOTS OF WORK FOR SIMPLE THINGS - CONTINUED

JDBC+ PROBLEM: MANUAL SAVING (INSERT/UPDATE) IS TEDIOUS 1 1 2 10 1 2 11 1 3 42 10 12 1 43 11 4 13 2 44 11 5 22 42 45 12 23 42 46 13 ... ...

OTHER JDBC+ PROBLEMS: • Limited caching – Caches only query results (by definition) – ORM can “understand” mutations, JDBC+ can’t • Fear of SQL – People problem – Training and tools help a lot

MIX APPROACHES TO CROSS THE CHASM: From ORM toward JDBC+ From JDBC+ toward ORM • Eager flushing • Save phase at the end • HQL, SQL queries • Get-by-id, update, insert, delete for each class • Form-based / non-generic • Active Record-like DAOs, development reflection + dynamic SQL • Discipline, examine the • Custom development inner workings

CONCLUSION • The ORM-SQL chasm might be scary • It’s not that wide • You can stay in the middle with some tricks

[Dolenc] Hibernate vs. iBatis

by javablend on Oct 14, 2008

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[Dolenc] Hibernate vs. iBatis — Presentation Transcript