Brief overview of different ways to work with legacy projects. Presentation for XPDays Ukraine 2014.

1. Legacy Projects
How to win the race

2. Legacy Projects
How to win the race

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

4. Legacy Projects History
2004
Others Java
2014
Others Java

5. What is…
…legacy projects?

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

7. Legacy
Crappy

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

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

10. Why Does…
…a legacy project born?

11. Time passed
Time
Because of time
Timepassed
Time
Because of time
Is it the ONLY reason?

14. Would you choose...

15. Shiny

16. Dull
Mainstream

18. Terrible
Project
Clean
Project
In future Now
Legacy

19. No escape

20. ReWRite…
…or not?

22. Failed somewhere?

23. Refactoring
…cookbook

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

25. Keep Stack Updated

27. Build Health

29. Bulk Code Changes

30. 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>

31. Prototyping

32. Scripting
Visio
Rational
Rose
Power
Designer

34. Maintain Clean Code

35. 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

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

37. Universal soldier...

38. 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

39. 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

40. JavaDoc... No, have never heard

41. 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

42. 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

43. Fail of fail-over protection

44. 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

45. Master class of API design

46. 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

47. Fatality!

48. 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

49. What Else?

50. Transaction Management
Dependency Injection
Mass Relocation
Various Migrations

51. Mindset
Prepare yourself

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

53. I cannot understand
It is a crap
Assumptions

54. I cannot understand
It may be a crap
Assumptions

56. Pet Clinic Comparison
Poor Successful
…
Carenot, killing
…
…
Care, not killing
…

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

58. Conclusions
Finally

59. 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

60. Questions
Thank you for attention