Code Generation with giant CRUD

Code generation with giant CRUD Tom Klaasen 10to1

Tom Klaasen Works professionally with Java since 1999  Co-founder of 10to1 (http://www.10to1.be)  Has worked on a project involving a lot of  code generation over the last 2 years tom@10to1.be  www.javapolis.com

Overall Presentation Goal Reducing typing with code generation www.javapolis.com

The question Who wants to type in 1000+ Java class files? www.javapolis.com

The problem Mission: “Create generic CRUD screens for  a domain model” www.javapolis.com 6

The problem “Our domain model will likely contain a few  hundred classes” www.javapolis.com 7

The problem “Oh, and we’re not sure which parts will  stay generic and which won’t” www.javapolis.com 8

The problem “And please, have it done in 3 months, with  4 developers” www.javapolis.com 9

The problem “And use RUP. But don’t wait for the  analysts to finish their job, because we don’t have that kind of time” Change your code when the Use Cases are  finished www.javapolis.com 10

The problem “(And don’t wait for the data modellers  either. We really don’t have any time.)” www.javapolis.com 11

The problem Domain model with 500+ classes  Each class: 1 interface, 2 implementations  Relations between those objects are first-  class citizens Also 1 interface, 2 implementations  Some classes have a lot of performance-  gaining methods Fine-grained getters and setters for the relations  Each class has 10+ attributes  Each needing a getter and a setter  www.javapolis.com

The problem For each domain class:  DAO  Manager  FormAction  form.jsp  searchform.jsp  list.jsp  editflow.xml  Another 1000 lines of Java, JSP and XML  code www.javapolis.com 13

The problem Result: 2000+ lines of code per domain  object For 4000 domain objects  Who wants to type these in?  www.javapolis.com 14

The problem Most of the constructs will change over  time 4000 x 2000 lines of code are subject to change  Who wants to make these corrections?  www.javapolis.com 15

Other constraints 2 years ago: beginning of 2005  Java 1.4  www.javapolis.com 16

The approach Generate everything  But: make it possible to hand-code  everything Attribute definitions: in the DB  www.javapolis.com 17

Generation process: first generation .hbm.xml DB Tables .jsp FormAction Domain DB .java Flow.xml Manager DAO www.javapolis.com 18

The tools AppFuse + AppGen  Ant  XDoclet  Hibernate  Home-written Access tool  www.javapolis.com 19

The tools XDoclet: extended with custom annotations  @gui hidden=”false”  @relation mandatory=”true”  www.javapolis.com 20

Disadvantages Ant: messed-up build scripts  XDoclet  2 ‘design decisions’ for each information to be  passed slow  www.javapolis.com 21

Improvements Maven  Clean project structure  FreeMarker  More flexible than XDoclet  Read directly from the DB  Don’t always generate everything  More and more hand-coded ‘generic’ files  As knowledge about the domain grew  www.javapolis.com 22

The end situation .hbm.xml DB Tables Domain DB .java .jsp www.javapolis.com 18 23

The pros Always flexible  When no knowledge available: generate  everything Override with hand-coded parts where necessary  When patterns and securities arise: hand-code  them in a generic way www.javapolis.com 24

Comparison with other solutions Hand-code everything (and every change)  Hire a lot of code monkeys  Design everything generically, correctly the  first time And good luck with that  Trails  Code is not generated  Thus impossible to override  Rails (with JRuby)  This started in 2005, remember?  www.javapolis.com 25

Conclusion Code generation can make you flexible and responsive. Do try this at home. (Or at work) www.javapolis.com

Q&A View JavaPolis talks @ www.parleys.com

Thank you for your attention

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Code Generation with giant CRUD

by Tom Klaasen

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