У вас древний проект? Все зовут его «Legacy», а вас «неудачник»? Возможно они даже смеются над вами. Давайте взглянем на ситуацию с другого ракурса. Все (все, Карл!) успешные проекты рано или поздно превращаются в Legacy-проекты. Я затрону тему Legacy не просто как явление, а как возможность быть постоянно в тренде, прослыть супер-спецом (даже если ты знаешь всего два фреймворка), сделать карьеру, как делать, то что ты хочешь, а не то что тебя просят. Ладно, ладно, я наврал про два фреймворка, но все остальное чистая правда. Я покажу, что вы можете творить, имея правильный подход к Legacy коду. Суть в том, что Legacy — это не грустно/уныло/немодно, это просто/клево/весело, если с умом подойти к задаче!

1. Legacy Projects
How to win the race

2. Victor Polischuk
Many years of
legacy systems
reviving and
refactoring
experience
Loves it
E-mail:
victor2@ukr.net
Skype:
victor-cr
Twitter:
@alkovictor

3. Legacy Projects History
2004
Others Java
2014
Others Java

4. What is…
…legacy projects?

5. Comparison Sheet
Legacy
Earned a fortune
Important
Predictable
Crappy
Designed by morons
Boring
Unmaintainable
No documentation

6. Legacy
Crappy

7. What is the main difference?
Happy owner
Better quality
No difference
Project cost

8. What is the main difference?
Happy owner
Better quality
No difference
Project cost

9. Why Does…
…a legacy project born?

10. Time
Timepassed
Time
Because of time
Tim
e
Time passed
Time
Time
Timepassed
Becauseoftim
e
Because of time
Because of time
Time passed
Time passed
Tim
e
Time
Time
Time passed
Time
Tim
e
Timepassed
Because of time
Time passed
Time passed
Tim
e
Time
Is it the ONLY reason?

11. You are an Architect

12. Brand new projectis waiting...

13. Would you choose...

14. Cutting Edge
Shiny

15. Dull
Mainstream

16. New
technologies
Challenge
unknown
Evolve
You are special
Boring stack
Challenge
patience
Nothing new
You are just
as everyone

17. Terrible
Project
Clean
Project
In future Now
Legacy

18. No escape
Legacy is
everywhere!

19. Rewrite…
…or not?

20. 1. Specify
2. Estimate
3. Compare
4. ?????
5. Profit!!!!!
Write down all requirements
Each module complexity
Pick reasonable bounds
?????
Happy dancing

21. Failed somewhere?

22. Refactoring
…cookbook

23. Boy-scout rule Libraries upgrade
Build migration Code transformation
Code generation Miscellaneous

24. Keep Stack Updated

25. Obsolete
Let’s upgrade
MigrationSanity Check
Production

26. Build Health

27. Checkout
/
Clone
Valid
Artefact
Test/Prod
Deploy

28. Bulk Code Changes

29. Know Your Tools
Regexp:
(?ms)publics+statics+([^{]+).*?(?=s+publics+|}s+z)
XSLT:
<xsl:stylesheet…>
<xsl:template match="/">
<beans>
<xsl:apply-templates
select="struts-config/action-mappings/*"/>
</beans>
</xsl:template>
<xsl:template match="action">
<bean id="{@path}" class="{@type}"/>
</xsl:template>
</xsl:stylesheet>

30. <struts-config>
…
<action-mappings>
…
<action path="/logon“ type="example.LogonAction">
<forward ... />
<exception ... />
</action>
<action type="example.LogoutAction" path="/logout"/>
…
</action-mappings>
…
</struts-config>
XSLT: Source

31. <xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<beans>
<xsl:apply-templates
select="struts-config/action-mappings/*"/>
</beans>
</xsl:template>
<xsl:template match="action">
<bean id="{@path}" class="{@type}"/>
</xsl:template>
</xsl:stylesheet>
XSLT: Template

32. <beans>
...
<bean id="/logon" class="example.LogonAction"/>
<bean id="/logout" class="example.LogoutAction"/>
...
</beans>
XSLT: Result

33. Prototyping

34. Scripting
Visio
Rational
Rose
Power
Designer

35. Script Data Model
Template
Engine
Generated
Prototype

36. Maintain Clean Code

37. ResultSet aResultSet = null;
ArrayList theAttribute1List = new ArrayList();
ArrayList theAttribute2List = new ArrayList();
…
ArrayList theAttribute30List = new ArrayList();
…
StringBuffer aQuery = new StringBuffer("select ")
.append("ATTRIBUTE1,")
.append("ATTRIBUTE2,")
…
while (aResultSet.next()) {
if (aResultSet.getString("ATTRIBUTE1") != null)
theAttribute1List.add(aResultSet.getString("ATTRIBUTE1"));
…
htAttributeList.put("ATTRIBUTE1", distinct(theAttribute1List));
htAttributeList.put("ATTRIBUTE2", distinct(theAttribute2List));
010

38. What have you done to prevent me seeing
it?

39. Universal soldier...

40. public class UniversalComparator implements Comparator {
…
if (value1 instanceof GregorianCalendar) {
GregorianCalendar lcal_obj1 = (GregorianCalendar) value1;
GregorianCalendar lcal_obj2 = (GregorianCalendar) value2;
boolean lb_value = lcal_obj1.before(lcal_obj2);
if (ii_comparatorDirection == COMP_ASC) {
if (lb_value == true) {
return 1;
} else {
return -1;
}
} else {
if (lb_value == true) {
return -1;
} else {
return 1;
}
}
} 07

41. if (value1 instanceof Boolean) {
Boolean lv_obj1 = (Boolean) value1;
Boolean lv_obj2 = (Boolean) value2;
String ls_value1 = lv_obj1.toString();
String ls_value2 = lv_obj2.toString();
logService.debug("compare: lb_value1, lb_value2: "
+ ls_value1 + ", " + ls_value2);
int lv_value1 = (ls_value1 == "true") ? 1 : 0;
int lv_value2 = (ls_value2 == "true") ? 1 : 0;
if (ii_comparatorDirection == COMP_ASC) {
int val = (lv_value1 < lv_value2) ? -1 : 1;
// log("val: " + val);
return (lv_value1 < lv_value2) ? -1 : 1;
} else
return (lv_value1 < lv_value2) ? 1 : -1;
}
06

42. Standard Library???
No, have never heard

43. private void moveFile(String from, String to) throws Exception {
//move files from 'from' to 'to'
String[] cmd;
if (File.separator.compareTo("") == 0) { //windows
cmd = new String[] {"cmd", "/c", "move",
from.trim().replace("/", File.separator),
to.trim().replace("/", File.separator)
};
} else {//linux like, simple mv command does not work, using script
cmd = new String[] {parameters.get("movePath") + ".sh",
from.trim().replace("/", File.separator),
to.trim().replace("/", File.separator)
};
}
System.gc(); //reduces current process size before fork
Process p = Runtime.getRuntime().exec(cmd);
p.waitFor();
p.destroy(); //free up memory
}
05

44. Code review?... WTF?
private static final List<Option> DEFAULT_OPTIONS =
new ArrayList<Option>(4);
{
DEFAULT_OPTIONS.add(new Option(1, "Unavailable"));
DEFAULT_OPTIONS.add(new Option(2, "Unidirectional"));
DEFAULT_OPTIONS.add(new Option(3, "Bidirectional"));
DEFAULT_OPTIONS.add(new Option(4, "Not applicable"));
}
04

45. Fail of fail-over protection

46. public static void lockPartyWithLog(Party p, UnitOfWork uow) {
// Local variables
Party partyClone = null;
// Lock the object
// LOCK_NOWAIT : an exception occurs if the object is being locked
try {
partyClone = (Party) uow.refreshAndLockObject(p,
ObjectLevelReadQuery.LOCK_NOWAIT);
} catch (DatabaseException dbe) {
logService.info("The party ID = " + p.getId()
+ " is locked by an other process");
try {
Thread.currentThread().sleep(1000);
} catch (Exception e) {
logService.error("Thread Exception ", e);
}
lockPartyWithLog(p, uow);
}
}
03

47. Master class of API design

48. public interface Parser {
void setReport(InputStream inputstream);
void setReport(String s);
String getReport();
void save();
void delete(String Query) throws HibernateException;
void setParams(Map<String, String> map);
Map<String, String> getParams();
void saveReport(String reportPath);
Boolean isDuplicated(String fileName);
}
23: public class PMScanReport extends AbstractParser
23: implements Parser {
..........
1556: }
02

49. Comparatality!

50. public int compare(TradeConfirmation tc1, TradeConfirmation tc2) {
int value;
Offer o1 = (Offer) tc1.getOffer();
Offer o2 = (Offer) tc2.getOffer();
if (o1.getTradingInterval() < o2.getTradingInterval()) {
value = -1;
} else {
if (o1.getTradingInterval() == o2.getTradingInterval()) {
if (o1.getType() < o2.getType()) {
value = -1;
} else {
if (o1.getType() == o2.getType()) {
PartyDef p1 = o1.getParty().getEffectiveNow();
PartyDef p2 = o2.getParty().getEffectiveNow();
if (p1.getName().compareTo(p2.getName()) < 0) {
value = -1;
} else {
if (p1.getName().compareTo(p2.getName()) == 0) {
if (o1.getTradingZone().getEffectiveNow().getIdentification().compareTo(…) < 0) {
value = -1;
} else {
if (o1.getTradingZone().getEffectiveNow().getIdentification().compareTo(…)) == 0) {
value = 0;
} else {
value = 1;
}
}
} else {
value = 1;
}
}
} else {
value = 1;
}
}
} else {
value = 1;
}
}
return value;
}
01

51. What Else?

52. Transaction Management
Dependency Injection
Mass Relocation
Various Migrations

53. Mindset
Prepare yourself

54. Legacy Law
Successful
Legacy Non-legacy
Legacy
Crappy Non-crappy

55. I cannot understand
It is a crap
Assumptions

56. I cannot understand
It may be a crap
Assumptions

57. Victim Warrior

58. Pet Clinic Comparison
Poor Successful
…
Care not, killing
…
…
Care, not killing
…

59. Who would you trust
with your most precious
pet?

60. Conclusions
Finally

61. Legacy is everywhere
• You cannot hide or pretend it has nothing to do with you
Legacy means success
• Truly crappy things do not live long
Knowledge is a weapon
• People feel calm when encounter known problems
Change your mindset
• It is up to you: run crying or deal with it like a boss
Trust is important
• It also influences your freedom in decision making

62. Questions
Thank you for attention