Surviving and working efficiently with legacy codes is becoming more and more of a nightmare for long running projects, big companies and young engineers. It’s becoming a norm in software development - thus modernizing and reimplementing them is deemed highly necessary. In this session let's take a deep look into how legacy codes are made and how we can safely refactor/reimplement them.

1. München/HQ Bamberg Berlin Đà Nẵng Dresden Grenoble Hamburg Cologne Leipzig Nuremberg Prague Washington Zug
Make Legacy Code Great Again
Ezekiel Olasehinde
Đà Nẵng, 11/07/2020

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About me
Software Engineer
IT Freak
Scrum
Master
Web
Application
Developer

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Basic attributes
not
documented
unsupported
technology
not tested
inherited

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How is legacy code made?
Technical Debt
Forgotten technology
Ignorance

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Technical Debt

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Refactoring is a control technique for improving the
design on an existing code base.
What is refactoring ?

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Why you should refactor?

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Unit test
Prevents regressions
Verification
Documentation

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Approval testing

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Fixing legacy codes – Where to start?

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Customer call

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One true legacy validation
…
…
public String doLegacyValidation(ValidatableUser validatableUser) {
//session based validation
if (!UserSession.getInstance().isUserLoggedIn() && validatableUser.isValidationAllowed()) {
return "Validation impossible with logged in user";
}
String errorMessage = "";
//email validation
if (StringUtils.isEmpty(validatableUser.getEmail())) {
errorMessage += "email is required";
} else if (!validatableUser.getEmail().contains("@")) errorMessage += "this is not an email n";
else if (validatableUser.getEmail().contains("@")) {
String[] emailSplit = validatableUser.getEmail().split("@");
if (emailSplit[1].split(".").length < 2)
errorMessage += "Unrecognized email pattern";
}
//zip code validation
try {
int zip = Integer.parseInt(validatableUser.getZipCode());
if (validatableUser.getZipCode().length() < 6) {
errorMessage += "zip code needs to be atleast of length of 6";
} else if (validatableUser.getZipCode().length() > 7) {
errorMessage += "zip code length must not be more than 7";
}
int countOfFives = 0;
for (int a = 0; a < validatableUser.getZipCode().length(); a++) {
if (validatableUser.getZipCode().charAt(a) == '5') {
countOfFives++;
}
}
if (countOfFives < 2) {
errorMessage += "zip code failed the requirement of atleast double 5";
}
if (StringUtils.pathEquals(validatableUser.getUsername(), validatableUser.getPassword().getKey())) {
errorMessage += "Invalid confirm password, kindly check our password policyn";
}
} catch (NumberFormatException n) {
errorMessage += "unrecognized zip code";
}
//username validation
if (Arrays.asList("admin", "systemadmin", "annoymous").contains(validatableUser.getUsername().toLowerCase())) {
errorMessage += "Invalid username, kindly check our username policyn";
} else if (length(validatableUser.getUsername(), ' ') < 6) {
errorMessage += "Invalid username, kindly check our username policyn";
} else if (length(validatableUser.getUsername(), ' ') > 10) {
errorMessage += "Invalid username, kindly check our username policyn";
}
//password validation
if (Arrays.asList("admin", "sysadmin", "anonymous").contains(validatableUser.getPassword().getKey().toLowerCase())) {
errorMessage += "Invalid password, kindly check our password policyn";
} else if (length(validatableUser.getPassword().getKey(), ' ') < 6) {
errorMessage += "Invalid password, kindly check our password policyn";
} else if (length(validatableUser.getPassword().getKey(), ' ') > 10) {
errorMessage += "Invalid password, kindly check our password policyn";
}
if (Arrays.asList("admin", "sysadmin", "anonymous").contains(validatableUser.getPassword().getValue().toLowerCase())) {
errorMessage += "Invalid confirm password, kindly check our password policyn";
} else if (length(validatableUser.getPassword().getValue(), ' ') < 6) {
errorMessage += "Invalid confirm password kindly check our password policyn";
} else if (length(validatableUser.getPassword().getValue(), ' ') > 10) {
errorMessage += "Invalid confirm password, kindly check our password policyn";
}
return errorMessage;
}
…
…

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Problem
...
...
if (!UserSession.getInstance().isUserLoggedIn() && validatableUser.isValidationAllowed())
{
return "Validation impossible with logged in user";
}
…
…

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Problem
//username validation
if (Arrays.asList("admin", "systemadmin",
"annoymous").contains(validatableUser.getUsername().toLowerCase())) {
errorMessage += "Invalid username, kindly check our username policyn";
} else if (length(validatableUser.getUsername(), ' ') < 6) {
errorMessage += "Invalid username, kindly check our username policyn";
} else if (length(validatableUser.getUsername(), ' ') > 10) {
errorMessage += "Invalid username, kindly check our username policyn";
}
…
…

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Eliminate singleton
private final UserSession userSession;
public boolean isValidationAllowed(ValidatableUser validatableUser) {
return !userSession.isUserLoggedIn() && validatableUser.isValidationAllowed();
}

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def userSession = Mock(UserSession)
@Subject
def validationProvider = new ValidationProvider(userSession)
@Unroll
def 'validate user session where validation allowed #validationAllowed and userlogged is #isloggedIn'() {
//validation tests
}
Test

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Approval Test

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Minimum refactoring
public String validateUsername(ValidatableUser validatableUser) {
String validationMessage;
//copied validation logic
...
...
return validationMessage;
}

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@Unroll
def 'validate username #username' () {
…
…
}
Test

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Approval Test

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Minimum refactoring
Zip code Password
Confirm
password

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More Refactoring

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Concept

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End Result
…
…
private final SystemWideUserValidator<RegistrationValidatableUser, DefaultValidationResult> systemWideUserValidator;
public DefaultValidationResult doLegacyValidation(RegistrationValidatableUser validatableUser) throws ValidationImpossibleException {
…..
…..
return systemWideUserValidator.validate(validatableUser);
}
…
…

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Refactoring Take Home
Always refactor
Test before
refactoring
Documentation
Don't focus
performance

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Innovation Implemented.
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