Spring, CDI, Jakarta EE good parts

SPRING, JAKARTA EE, CDISPRING, JAKARTA EE, CDI
and otherand otherand other pathologiespathologiespathologies

JAREK RATAJSKIJAREK RATAJSKI
Software Developer, Wizard, AnarchitectSoftware Developer, Wizard, AnarchitectSoftware Developer, Wizard, Anarchitect
at Engenius GmbHat Engenius GmbHat Engenius GmbH

@ Engeniush GmbH@ Engeniush GmbH@ Engeniush GmbH
Yes, we hireYes, we hireYes, we hire

Pros:Pros:Pros:
No table football

Cons:Cons:Cons:
you have to talk to people

I WORK WITH JAVA EE SINCE ~2001I WORK WITH JAVA EE SINCE ~2001
WITH SPRING SINCE 2006WITH SPRING SINCE 2006
I remember EJB-OSS
and huge xmls in Spring

At the moment I amAt the moment I amAt the moment I am making my hands dirty in about 15 various Springmaking my hands dirty in about 15 various Springmaking my hands dirty in about 15 various Spring
and Java EE projectsand Java EE projectsand Java EE projects

I code for only few projects that are notI code for only few projects that are notI code for only few projects that are not SpringSpringSpring
ororor Java EEJava EEJava EE basedbasedbased

I code for only few projects that are notI code for only few projects that are notI code for only few projects that are not SpringSpringSpring
ororor Java EEJava EEJava EE basedbasedbased
including one very critical application (netty based)including one very critical application (netty based)including one very critical application (netty based)

⚠ I like xing production bugs:⚠ I like xing production bugs:⚠ I like xing production bugs:

⚠ I like xing production bugs:⚠ I like xing production bugs:⚠ I like xing production bugs:
Concurrency, security, performance, heisenbugsConcurrency, security, performance, heisenbugsConcurrency, security, performance, heisenbugs

As I have some Java EE, Spring experienceAs I have some Java EE, Spring experienceAs I have some Java EE, Spring experience

I think,I think,I think,

they are doing too much harm to your code (architecture)they are doing too much harm to your code (architecture)they are doing too much harm to your code (architecture)

they are doing too much harm to your code (architecture)they are doing too much harm to your code (architecture)they are doing too much harm to your code (architecture)
we have to do betterwe have to do betterwe have to do better

STORY OFSTORY OF GO TOGO TO ((GOTOGOTO))

GO TO STATEMENT CONSIDERED HARMFULGO TO STATEMENT CONSIDERED HARMFUL
March 1968,March 1968,March 1968, Edsger W. DijkstraEdsger W. DijkstraEdsger W. Dijkstra

E.D.E.D.E.D.
For a number of years I have been familiar with theFor a number of years I have been familiar with theFor a number of years I have been familiar with the
observation that the quality of programmers is aobservation that the quality of programmers is aobservation that the quality of programmers is a
decreasing function of the density of go todecreasing function of the density of go todecreasing function of the density of go to
statements in the programs they produce. Morestatements in the programs they produce. Morestatements in the programs they produce. More
recently I discovered why the use of the go torecently I discovered why the use of the go torecently I discovered why the use of the go to
statement has such disastrous e ects, and I becamestatement has such disastrous e ects, and I becamestatement has such disastrous e ects, and I became
convinced that the go to statement should beconvinced that the go to statement should beconvinced that the go to statement should be
abolished from all "higher level" programmingabolished from all "higher level" programmingabolished from all "higher level" programming
languages (i.e. everything except, perhaps, plainlanguages (i.e. everything except, perhaps, plainlanguages (i.e. everything except, perhaps, plain
machine code). At that time I did not attach toomachine code). At that time I did not attach toomachine code). At that time I did not attach too
much importance to this discovery; I now submit mymuch importance to this discovery; I now submit mymuch importance to this discovery; I now submit my
considerations for publication because in veryconsiderations for publication because in veryconsiderations for publication because in very
recent discussions in which the subject turned up, Irecent discussions in which the subject turned up, Irecent discussions in which the subject turned up, I
have been urged to do so.have been urged to do so.have been urged to do so.

GOT0 CONSIDERED HARMFUL - CONSIDERED HARMFULGOT0 CONSIDERED HARMFUL - CONSIDERED HARMFUL
March 1987, Frank RubinMarch 1987, Frank RubinMarch 1987, Frank Rubin

F.R.F.R.F.R.
GOTO-less programs are harder and costlier toGOTO-less programs are harder and costlier toGOTO-less programs are harder and costlier to
create, test, and modify.create, test, and modify.create, test, and modify.

F.R.F.R.F.R.
AsAsAs I introduce GOTOs to untangleI introduce GOTOs to untangleI introduce GOTOs to untangle each deeplyeach deeplyeach deeply
nested mess of code,nested mess of code,nested mess of code, I have found that the numberI have found that the numberI have found that the number
of lines of code often drops byof lines of code often drops byof lines of code often drops by 20-25 percent,20-25 percent,20-25 percent,

F.R.F.R.F.R.
I am aware that some awful programs have beenI am aware that some awful programs have beenI am aware that some awful programs have been
written usingwritten usingwritten using GOTOs. This is often the fault ofGOTOs. This is often the fault ofGOTOs. This is often the fault of thethethe
language (because it lackslanguage (because it lackslanguage (because it lacks other constructs), or theother constructs), or theother constructs), or the
text editor (because it lacks a blocktext editor (because it lacks a blocktext editor (because it lacks a block move). With amove). With amove). With a
proper languageproper languageproper language and editor, and adequateand editor, and adequateand editor, and adequate
instruction in the use of GOTO, thisinstruction in the use of GOTO, thisinstruction in the use of GOTO, this should not be ashould not be ashould not be a
consideration.consideration.consideration.

somesomesome C# .NetC# .NetC# .Net code presented to proove howcode presented to proove howcode presented to proove how COOLCOOLCOOL goto is (at polishgoto is (at polishgoto is (at polish
4programmers message board)4programmers message board)4programmers message board)
private static bool TryParseSByteD(ReadOnlySpan<byte> source, out sbyte value, out int bytesConsumed)
{
if (source.Length < 1)
goto FalseExit;
int sign = 1;
int index = 0;
int num = source[index];
if (num == '-')
{
sign = -1;
index++;
if ((uint)index >= (uint)source.Length)
goto FalseExit;
num = source[index];
}
else if (num == '+')
{
index++;
goto FalseExit;
}
int answer = 0;
if (ParserHelpers.IsDigit(num))
{
if (num == '0')
{
do
{
index++;
goto Done;
} while (num == '0');
if (!ParserHelpers.IsDigit(num))
goto Done;
}
answer = num - '0';
index++;
goto Done;
if (!ParserHelpers.IsDigit(num))
goto Done;
index++;
answer = 10 * answer + num - '0';
// Potential overflow
goto Done;

ON A SOMEWHAT DISAPPOINTING CORRESPONDENCEON A SOMEWHAT DISAPPOINTING CORRESPONDENCE
May 1987, Edsger W. DijkstraMay 1987, Edsger W. DijkstraMay 1987, Edsger W. Dijkstra

E.D.E.D.E.D.
By my standards, a competent professionalBy my standards, a competent professionalBy my standards, a competent professional
programmer in 1987programmer in 1987programmer in 1987
should recognize that Rubin’s problem asks to be
solved by a nested application of the same
algorithm;
should know the theorem of “The bounded linear
search”;
should be able to derive that theorem and its
proof;
should not hesitate to use it;
should not waste his time in pointing out that the
boolean variable d is super uous;
should keep his repetitions simple and
disentangled;
etc. . .

It is typically possible to show how greatIt is typically possible to show how greatIt is typically possible to show how great GO TOGO TOGO TO is,is,is, on a small selectedon a small selectedon a small selected
piece of codepiece of codepiece of code
it is performantit is performantit is performant
write nowwrite nowwrite now - jump anywhere- jump anywhere- jump anywhere

BrokenBrokenBroken local reasoninglocal reasoninglocal reasoning

BrokenBrokenBroken local reasoninglocal reasoninglocal reasoning
how much code do you have to read when something does not workhow much code do you have to read when something does not workhow much code do you have to read when something does not work

MAINSTREAM INDUSTRY STOPPED USINGMAINSTREAM INDUSTRY STOPPED USING "GOTO""GOTO" DECADESDECADES
AGOAGO
Costs (risks) are greater thanCosts (risks) are greater thanCosts (risks) are greater than pro tspro tspro ts

10:10: BeansBeans (AS YOU KNOW) ARE(AS YOU KNOW) ARE "GOTOs""GOTOs" OF JAVAOF JAVA

Forget about classicForget about classicForget about classic JavaBeansJavaBeansJavaBeans

Forget about classicForget about classicForget about classic JavaBeansJavaBeansJavaBeans
This is closed topic,This is closed topic,This is closed topic, we don't gowe don't gowe don't go there anymorethere anymorethere anymore

SPRING BEANS, JAVA EE BEANS, CDI BEANS, JSF,SPRING BEANS, JAVA EE BEANS, CDI BEANS, JSF,
JPA...JPA...

BEAN == MUTILATED, CRIPPLED CLASS(OBJECT) IN JAVABEAN == MUTILATED, CRIPPLED CLASS(OBJECT) IN JAVA

Looks like normal object, but does not behave (like) normalLooks like normal object, but does not behave (like) normalLooks like normal object, but does not behave (like) normal

Not instantiated by new

Not instantiated by new
there are special rules, limitations, conventions on use

BEANS, BUT WHY?BEANS, BUT WHY?

20: DISASTER NO. 120: DISASTER NO. 1

dependency injectiondependency injectiondependency injection - what is a DI?- what is a DI?- what is a DI?

WikipediaWikipediaWikipedia
In software engineering, dependency injection is aIn software engineering, dependency injection is aIn software engineering, dependency injection is a
technique whereby one object supplies thetechnique whereby one object supplies thetechnique whereby one object supplies the
dependencies of another object. A "dependency" isdependencies of another object. A "dependency" isdependencies of another object. A "dependency" is
an object that can be used, for example a service.an object that can be used, for example a service.an object that can be used, for example a service.
Instead of a client specifying which service it willInstead of a client specifying which service it willInstead of a client specifying which service it will
use, something tells the client what service to use.use, something tells the client what service to use.use, something tells the client what service to use.
The "injection" refers to the passing of a dependencyThe "injection" refers to the passing of a dependencyThe "injection" refers to the passing of a dependency
(a service) into the object (a client) that would use it.(a service) into the object (a client) that would use it.(a service) into the object (a client) that would use it.
The service is made part of the client's state.[1]The service is made part of the client's state.[1]The service is made part of the client's state.[1]
Passing the service to the client, rather thanPassing the service to the client, rather thanPassing the service to the client, rather than
allowing a client to build or nd the service, is theallowing a client to build or nd the service, is theallowing a client to build or nd the service, is the
fundamental requirement of the pattern.fundamental requirement of the pattern.fundamental requirement of the pattern.

Passing the service to the client, rather thanPassing the service to the client, rather thanPassing the service to the client, rather than
allowing a client to build or nd the service, is theallowing a client to build or nd the service, is theallowing a client to build or nd the service, is the
fundamental requirement of the pattern.fundamental requirement of the pattern.fundamental requirement of the pattern.

Do we have aDo we have aDo we have a dependency injectiondependency injectiondependency injection here?here?here?
class MyService {
private final DbRepo db;
public MyService() {
this.db = new DbRepo("jdbc://url")
}
}

Do we have aDo we have aDo we have a dependency injectiondependency injectiondependency injection here?here?here?
class MyService {
private final DbRepo db;
public MyService(DbRepo db) {
this.db = db;
}
}
MyService serviceProvider() {
var db = new DbRepo("jdbc://url")
return MyService(db)
}

https://sites.google.com/site/unclebobconsultingllc/blogs-by-robert-https://sites.google.com/site/unclebobconsultingllc/blogs-by-robert-https://sites.google.com/site/unclebobconsultingllc/blogs-by-robert-
martin/dependency-injection-inversionmartin/dependency-injection-inversionmartin/dependency-injection-inversion
Dependency Injection doesn’t require a framework;Dependency Injection doesn’t require a framework;Dependency Injection doesn’t require a framework;
it just requires that you invert your dependenciesit just requires that you invert your dependenciesit just requires that you invert your dependencies
and then construct and pass your arguments toand then construct and pass your arguments toand then construct and pass your arguments to
deeper layers.deeper layers.deeper layers.

Framework (IoC container) lets youFramework (IoC container) lets youFramework (IoC container) lets you injectinjectinject at aat aat a small costsmall costsmall cost

Framework (IoC container) lets youFramework (IoC container) lets youFramework (IoC container) lets you injectinjectinject at aat aat a small costsmall costsmall cost
It is in fact technical debt - you will pay laterIt is in fact technical debt - you will pay laterIt is in fact technical debt - you will pay later

Typical Spring (DI) application architectureTypical Spring (DI) application architectureTypical Spring (DI) application architecture (simpli ed)(simpli ed)(simpli ed)

Repository in Controller - no problemRepository in Controller - no problemRepository in Controller - no problem

HttpRequest in Persistence layer - no problemHttpRequest in Persistence layer - no problemHttpRequest in Persistence layer - no problem

Injecting anything anywhere - no problemInjecting anything anywhere - no problemInjecting anything anywhere - no problem

Injecting anything anywhere - no problemInjecting anything anywhere - no problemInjecting anything anywhere - no problem
Bean transferred diseases - gratisBean transferred diseases - gratisBean transferred diseases - gratis

Beans just pretend they are not infamousBeans just pretend they are not infamousBeans just pretend they are not infamous SingletonSingletonSingletonsss

Only bad developers do thisOnly bad developers do thisOnly bad developers do this

Only bad developers do thisOnly bad developers do thisOnly bad developers do this
oh, really?oh, really?oh, really?

It is likeIt is likeIt is like GO TOGO TOGO TO

Sooner or later someone will make a shortcut an hour before DEMOSooner or later someone will make a shortcut an hour before DEMOSooner or later someone will make a shortcut an hour before DEMO
An it will stay like that -An it will stay like that -An it will stay like that - foreverforeverforever
Because, the most important things in agile are:Because, the most important things in agile are:Because, the most important things in agile are:

Sooner or later someone will make a shortcut an hour before DEMOSooner or later someone will make a shortcut an hour before DEMOSooner or later someone will make a shortcut an hour before DEMO
An it will stay like that -An it will stay like that -An it will stay like that - foreverforeverforever
Because, the most important things in agile are:Because, the most important things in agile are:Because, the most important things in agile are:
VelocityVelocityVelocity and niceand niceand nice burndown chartsburndown chartsburndown charts

LOBOLOBO
Level of Beans obscurityLevel of Beans obscurityLevel of Beans obscurity
(same for Jakarta EE -(same for Jakarta EE -(same for Jakarta EE - CDICDICDI @Inject@Inject@Inject, EJB, EJB, EJB @EJB@EJB@EJB ...)...)...)

It is evenIt is evenIt is even pro containerspro containerspro containers argument !argument !argument !
Would you write all those hundreds of injectionsWould you write all those hundreds of injectionsWould you write all those hundreds of injections
manually?manually?manually?

Step 0Step 0Step 0
class A {
@Autowired
Xx;
@Autowired
Y y;
@AUtowired
Z z;
}

Step 1Step 1Step 1
((( )))
class A {
final X x;
final Y y;
final Z z;
@Autowired
A(X x, Y y, Z z) {
this.x =x; this.y = y; this.z = z;
}
}
http://olivergierke.de/2013/11/why- eld-injection-is-evil/http://olivergierke.de/2013/11/why- eld-injection-is-evil/http://olivergierke.de/2013/11/why- eld-injection-is-evil/

Step 2Step 2Step 2
class A {
final X x;
final Y y;
final Z z;
//@Autowired
A(X x, Y y, Z z) {
this.x =x; this.y = y; this.z = z;
}
}

BACK TO CODING SCHOOL:BACK TO CODING SCHOOL:

If code is repeated - extract it to functionIf code is repeated - extract it to functionIf code is repeated - extract it to function

Sections of repeatingSections of repeatingSections of repeating newnewnew can be as well extractedcan be as well extractedcan be as well extracted

Use factories / providersUse factories / providersUse factories / providers

Use factories / providersUse factories / providersUse factories / providers
Too many arguements in constructor? Split a class in two (or three) (!)Too many arguements in constructor? Split a class in two (or three) (!)Too many arguements in constructor? Split a class in two (or three) (!)

PLENTY OF "BEANS" HAVE EXACTLY ONEPLENTY OF "BEANS" HAVE EXACTLY ONE
IMPLEMENTATIONIMPLEMENTATION

Services, Controllers...Services, Controllers...Services, Controllers...

Services, Controllers...Services, Controllers...Services, Controllers...
You don't need to make everything injectableYou don't need to make everything injectableYou don't need to make everything injectable

EXAMPLE (IN KOTLIN + VAVR)EXAMPLE (IN KOTLIN + VAVR)
data class StonesModule(
private val seq: DbSequence = DbSequence(),
val stoneRepo: Lazy<StoneRepo> = Lazy.of { StoneRepo(seq) },
val stoneService: Lazy<StoneService> = Lazy.of {StoneService
val stoneRest: Lazy<StoneRest> = Lazy.of {StoneRest(stoneSer
) //this is Kotlin uber constructor
// somewhere else
val myModule = StoneRepo( stoneRepo = Lazy.of{MyRepo()})
val service = myModule.stoneService.get()

"MANUAL" DI VS FRAMEWORK"MANUAL" DI VS FRAMEWORK
Manual DI vs container IoC
small pain every day <--> no problem for months - the disaster
tree like structure <--> ball of mud (messy cake)
3 - 6 deps per class <--> 5 - 18 deps per class (LOBO)

THERE ARE BEANS WORSE THAN SINGLETONS....THERE ARE BEANS WORSE THAN SINGLETONS....

Request scoped

Request scoped
Session scoped

Request scoped
Session scoped
ThreadLocal based

Request scoped
Session scoped
ThreadLocal based
Those are in factThose are in factThose are in fact global variablesglobal variablesglobal variables

private C method1( A a, B b) {
//uses a, b, and this. fields
this.serviceX.method2(a); //does not use `b`
this.serviceY.method3(b); //method does not use `a`
}

@Component
@Scope(value = WebApplicationContext.SCOPE_REQUEST, proxyMode = ScopedProxyMode.TARGET_CLASS)
class TrollService {
public A getA() {
return a;
}
public void setA(A a) {
this.a = a;
}
private A a;
}
@Service
public class ServiceX {
@Autowired
private TrollService trollService;
void method2(A a) {
trollService.setA(a);
}
}

In spring based projects this isIn spring based projects this isIn spring based projects this is normalnormalnormal
(especially in Spring batch)(especially in Spring batch)(especially in Spring batch)

BrokenBrokenBroken Local reasoningLocal reasoningLocal reasoning

OUTCOME:OUTCOME:
Many of small, reasonable changesMany of small, reasonable changesMany of small, reasonable changes can break your systemcan break your systemcan break your system

OUTCOME:OUTCOME:
and tests are still green (because they test only mocks)and tests are still green (because they test only mocks)and tests are still green (because they test only mocks)

OUTCOME:OUTCOME:
and tests are still green (because they test only mocks)and tests are still green (because they test only mocks)and tests are still green (because they test only mocks)
Sleep well, all yourSleep well, all yourSleep well, all your tests are greentests are greentests are green

Slaying Sacred Cows: Deconstructing Dependency InjectionSlaying Sacred Cows: Deconstructing Dependency InjectionSlaying Sacred Cows: Deconstructing Dependency Injection
Tomer GabelTomer GabelTomer Gabel

2005:2005: DISASTER NO. 2DISASTER NO. 2

WhenWhenWhen @Transactional@Transactional@Transactional does not work?does not work?does not work?

private method

private method
public, but this.call(...)

private method
object instantiated with new

private method
kotlin nal class/method (*)

private method
called in other thread (parallelStream(), future)

private method
troll aspekt (@Trollsactional)

private method
troll aspekt (@Trollsactional)
missing jar on server

ADDADD JPA MAGIC ON TOP OF THATJPA MAGIC ON TOP OF THAT
other magic Beans
managed
detached
dirty check
proxy

ADDADD TRANSACTION ISOLATION LEVEL ASSOCIATED ISSUESTRANSACTION ISOLATION LEVEL ASSOCIATED ISSUES
A.C.I.D.A.C.I.D.

Spring withSpring withSpring with @Transactional@Transactional@Transactional andandand JPA, and Database all togetherJPA, and Database all togetherJPA, and Database all together

IfIfIf @Transactional@Transactional@Transactional does not work - where do you put a breakpoint?does not work - where do you put a breakpoint?does not work - where do you put a breakpoint?

All aspects induce similar problems:All aspects induce similar problems:All aspects induce similar problems:
@Secured
@RolesAllowed
@Cacheable
@Lock
...

@Secured
@RolesAllowed
@Cacheable
@Lock
...
Can your company accept that those aspects may beCan your company accept that those aspects may beCan your company accept that those aspects may be not active onnot active onnot active on
productionproductionproduction???

@Secured
@RolesAllowed
@Cacheable
@Lock
...
Can your company accept that those aspects may beCan your company accept that those aspects may beCan your company accept that those aspects may be not active onnot active onnot active on
productionproductionproduction???
after small refactoring ?after small refactoring ?after small refactoring ?

Those are just NOTThose are just NOTThose are just NOT edge casesedge casesedge cases

It happens more often than you thinkIt happens more often than you thinkIt happens more often than you think

Some of the problems (like async) are solved by another set ofSome of the problems (like async) are solved by another set ofSome of the problems (like async) are solved by another set of
annotationsannotationsannotations
@AspectJ,
@PostConstruct,
@EnableAsync,
@EnableScheduling,
@NoRepositoryBean

Bean based development - a gentle introductionBean based development - a gentle introductionBean based development - a gentle introduction

MAGIC IN CODEMAGIC IN CODE
actually false (useless) de nitionactually false (useless) de nitionactually false (useless) de nition

MAGIC IN CODEMAGIC IN CODE
actually false (useless) de nitionactually false (useless) de nitionactually false (useless) de nition
THINGS, WE DO NOTTHINGS, WE DO NOT
UNDERSTANDUNDERSTAND

MAGIC INMAGIC IN CODECODE
practical de nition (v2.0practical de nition (v2.0practical de nition (v2.0 stable)stable)stable)

MAGIC INMAGIC IN CODECODE
practical de nition (v2.0practical de nition (v2.0practical de nition (v2.0 stable)stable)stable)
THINGS,THINGS, THAT DO NOTTHAT DO NOT
COMPOSE SAFELYCOMPOSE SAFELY

John De GoesJohn De GoesJohn De Goes

John de Goes (again)John de Goes (again)John de Goes (again)
Magic is a feature with non-compositionalMagic is a feature with non-compositionalMagic is a feature with non-compositional
semantics that succeeds in making thesemantics that succeeds in making thesemantics that succeeds in making the commoncommoncommon
case easy, at the cost of making the uncommoncase easy, at the cost of making the uncommoncase easy, at the cost of making the uncommon
cases surprising, impossible, or ridiculouslycases surprising, impossible, or ridiculouslycases surprising, impossible, or ridiculously
complex.complex.complex.

MAGICMAGIC
Dynamic proxy
Thread local
Runtime re ection
Instrumentation
bytecode manipulation
Stringly typed annotations

@Retryable
void myMethod () {
}

@Transactional
void myMethod () {
}

@Transactional
@Retryable
void myMethod () {
}

Is retry inside transaction or transaction inside retry?Is retry inside transaction or transaction inside retry?Is retry inside transaction or transaction inside retry?
@Transactional
@Retryable
void myMethod () {
}

Is retry inside transaction or transaction inside retry?Is retry inside transaction or transaction inside retry?Is retry inside transaction or transaction inside retry?
cache?, security? -> have funcache?, security? -> have funcache?, security? -> have fun
@Transactional
@Retryable
void myMethod () {
}

(hidden) cost of beans magic:(hidden) cost of beans magic:(hidden) cost of beans magic:
Heisenbugs
Stopped development
Unrealistic tests ( no aspects covered)
Slow tests (with aspects)
Overmocking (aka Mocksturbation, ...sorry)
Fear of refactoring
classpath / classloader disasters (on application servers)
problem with new java versions (not in Spring)
ugly architecture with shortcuts

SPRING IS NOT SIMPLESPRING IS NOT SIMPLE

666: MY TOP 3 - MOST666: MY TOP 3 - MOST
DANGEROUS (MAGIC) TOOLSDANGEROUS (MAGIC) TOOLS

3. JPA3. JPA
void method(User user) {
user.setName("Irek"); //will be saved?
user.getGroups().forEach(...); //will work?
}

3. JPA3. JPA
Depends: isDepends: isDepends: is bean managed (tracked in JPA session),bean managed (tracked in JPA session),bean managed (tracked in JPA session),
}

3. JPA3. JPA
Depends: isDepends: isDepends: is bean managed (tracked in JPA session),bean managed (tracked in JPA session),bean managed (tracked in JPA session),
waswaswas getGroupsgetGroupsgetGroups called before?called before?called before?
}

JPA Totally breaksJPA Totally breaksJPA Totally breaks local reasoninglocal reasoninglocal reasoning

People generally know SQLPeople generally know SQLPeople generally know SQL
ThenThenThen spend hours translating SQL to JPAspend hours translating SQL to JPAspend hours translating SQL to JPA

And they useAnd they useAnd they use .save().save().save() for updatesfor updatesfor updates

And they useAnd they useAnd they use .save().save().save() for updatesfor updatesfor updates
Which means probably - they have no clueWhich means probably - they have no clueWhich means probably - they have no clue

2. APPLICATION SERVERS2. APPLICATION SERVERS
Websphere, JBoss, Tomcat
Classpath problems
vendor lock-in / java version lock-in
lost in debug
testability(*) way worse than in Spring (I am looking at you
Arquillian)

1. JSF1. JSF
Maybe not the worst web framework ever doneMaybe not the worst web framework ever doneMaybe not the worst web framework ever done
ButButBut it sets the bar pretty highit sets the bar pretty highit sets the bar pretty high (for evil ones)(for evil ones)(for evil ones)
SessionScope hell
disaster in phases
resource consumption (Memory)
funny integration problems with other Beans

HOW ALL THAT HAPPENED?HOW ALL THAT HAPPENED?

Long time ago...Long time ago...Long time ago...

JAVA EE (1.X, 2.X)JAVA EE (1.X, 2.X)
Enterprise Java Bean - remote objects (better CORBA/RMI)
No one simply crates remote objects by new
Java EE/EJB - RMI on steroids
distributed transactions
2 phase commit
security in remote calls

SERVLETSSERVLETS
Classpath scan
instantiation by a container
default constructor

How can you test it?How can you test it?How can you test it?
public class HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResp
throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("<h1>" + message + "</h1>");
}
}

ONCE WE HAD NO GENERICS (BEFORE JAVA 5)ONCE WE HAD NO GENERICS (BEFORE JAVA 5)
//java 5
interface Provider<T> {
T getService();
}
//java 1.4
interface Provider {
Object getService();
}

NO LAMBDAS (BEFORENO LAMBDAS (BEFORE JAVA 8)JAVA 8)
"Aspect" done in a proper way"Aspect" done in a proper way"Aspect" done in a proper way
void <R> R doInTranasction( Funtion<DBTRansaction, R> code) {
var trx = b.beginTransaction();
try {
var result = code.apply(trx);
trx.commit();
return result;
} catch (...) {
trx.rollback();
throw ...
}
}

AT THE TIME OF JAVA 1.4AT THE TIME OF JAVA 1.4
Spring was e cient way of creating web applicationsSpring was e cient way of creating web applicationsSpring was e cient way of creating web applications

Up to java 7 there were not that many sensible alternativesUp to java 7 there were not that many sensible alternativesUp to java 7 there were not that many sensible alternatives

From javaFrom javaFrom java 8 on8 on8 on

We can use lambdas to provide similar functionality as aspects in aWe can use lambdas to provide similar functionality as aspects in aWe can use lambdas to provide similar functionality as aspects in a
compile safe waycompile safe waycompile safe way - without magic- without magic- without magic

We can use lambdas to provide similar functionality as aspects in aWe can use lambdas to provide similar functionality as aspects in aWe can use lambdas to provide similar functionality as aspects in a
compile safe waycompile safe waycompile safe way - without magic- without magic- without magic
We have mature alternatives to servlets (netty, ratpack, sparkjava,We have mature alternatives to servlets (netty, ratpack, sparkjava,We have mature alternatives to servlets (netty, ratpack, sparkjava,
spring web ux)spring web ux)spring web ux)

PSYCHOLOGICAL ASPECTSPSYCHOLOGICAL ASPECTS
everybody Java EE / Spring
magic is great (it worked again, miracle, wow)
Stockholm syndrome
developers ignore costs (risks)

STEP 1STEP 1
Drop application serversDrop application serversDrop application servers
Make Jar not War (Make Jar not War (Make Jar not War ( SpringBootSpringBootSpringBoot is good for a start)is good for a start)is good for a start)
use Kotlinuse Kotlinuse Kotlin
use vavr.iouse vavr.iouse vavr.io

STEP 2STEP 2
Hold your BeansHold your BeansHold your Beans
Use Beans where really neededUse Beans where really neededUse Beans where really needed
(example -> only(example -> only(example -> only Jax-RS annotations andJax-RS annotations andJax-RS annotations and @Controllers@Controllers@Controllers)))
Only constructors for DIOnly constructors for DIOnly constructors for DI

STEP 3STEP 3
(fun starts)(fun starts)(fun starts)
Drop JPADrop JPADrop JPA
Try:Try:Try: JOOQ, QueryDSL and alternativesJOOQ, QueryDSL and alternativesJOOQ, QueryDSL and alternatives

STEP 4STEP 4
Go functionsGo functionsGo functions

Spring WebFlux (withoutSpring WebFlux (withoutSpring WebFlux (without beans)beans)beans)
class WisniaServer {
fun start() {
val route = router {
GET("/hello", handle(::printHello))
GET("/helloUser", secure(handle(::printlHelloForUser)))
}
val httpHandler = RouterFunctions.toHttpHandler(route)
val adapter = ReactorHttpHandlerAdapter(httpHandler)
val server = HttpServer
.create()
.host("localhost")
.port(8080)
.handle(adapter)
.bindNow()
println("press enter")
readLine()
server.disposeNow()
}
}

This line:This line:This line:
secure(handle(::printlHelloForUser)))

This all works nicelyThis all works nicelyThis all works nicely in:in:in:

SPRINGSPRING

SPRINGSPRING
SPRING WEBFLUXSPRING WEBFLUX

SPRINGSPRING
SPRING WEBFLUXSPRING WEBFLUX
FullyFullyFully functionalfunctionalfunctional syntax, no beans, no annotations, no aspects neededsyntax, no beans, no annotations, no aspects neededsyntax, no beans, no annotations, no aspects needed

No classpath scanning -> SpringWeb ux starts in 200msNo classpath scanning -> SpringWeb ux starts in 200msNo classpath scanning -> SpringWeb ux starts in 200ms
Ratpack (alternative) starts in 10msRatpack (alternative) starts in 10msRatpack (alternative) starts in 10ms

Testing ofTesting ofTesting of functionalfunctionalfunctional applications is fast and easyapplications is fast and easyapplications is fast and easy
var app = Application(withMyTestDB).start();
var result = app.myApiCall();
assertEquals(expectedResult, result);

STEP 5 (REAL FUN)STEP 5 (REAL FUN)
Go monadsGo monadsGo monads
Transaction is a monadTransaction is a monadTransaction is a monad

Example usingExample usingExample using NeeNeeNee project for aspectsproject for aspectsproject for aspects
fun addNewStone(newStone: StoneData) = seq.next().flatMap {
addStone(it, newStone)
}
private fun addStone(stoneId : Long, newStone: StoneData)
= Nee.constP(transactional) { jdbcProvider ->
val dsl = DSL.using(jdbcProvider.getConnection().getResource())
val insertedRows = dsl.insertInto(Stones.STONES)
.values(stoneId, newStone.name, newStone.price)
.execute()
if (insertedRows == 1) {
Option.some(stoneId)
} else {
Option.none()
}
}

Instead of writing:Instead of writing:Instead of writing:
Write this:Write this:Write this:
class Hasiok {
@Resource
val jdbcConnection: Connection
@Transactional
@Secure
@Cacheable
@Retryable
fun f(p:P) {
//code
}
}
class Hasiok {
private val f = {jdbcConnection:Connection ->
{p: P ->
//code
}
}
val enterprisyF = Nee.pure(
secure
.and(retryable)
.and(cacheable)
.and(transactional), f)
}

We need time to adopt to new things /We need time to adopt to new things /We need time to adopt to new things / conceptconceptconcept
I understand you still use spring in 2019I understand you still use spring in 2019I understand you still use spring in 2019
Reduce risks / harmReduce risks / harmReduce risks / harm

Bill G icker image (Bill G icker image (Bill G icker image ( )))https://www. ickr.com/photos/billerr/1814657036https://www. ickr.com/photos/billerr/1814657036https://www. ickr.com/photos/billerr/1814657036

Bill G icker image (Bill G icker image (Bill G icker image ( )))
Baby stepsBaby stepsBaby steps
https://www. ickr.com/photos/billerr/1814657036https://www. ickr.com/photos/billerr/1814657036https://www. ickr.com/photos/billerr/1814657036

Spring 5 -> Spring Web ux is a huge step towards fpSpring 5 -> Spring Web ux is a huge step towards fpSpring 5 -> Spring Web ux is a huge step towards fp

I have clean spring web ux based applications without beans !!!I have clean spring web ux based applications without beans !!!I have clean spring web ux based applications without beans !!!

Spring is not like a WAR (or Java EE)Spring is not like a WAR (or Java EE)Spring is not like a WAR (or Java EE)

It changesIt changesIt changes

maybe one day spring will not promote beans anymore?maybe one day spring will not promote beans anymore?maybe one day spring will not promote beans anymore?

maybe one day spring will not promote beans anymore?maybe one day spring will not promote beans anymore?maybe one day spring will not promote beans anymore?
They have stopped with XMLs some time agoThey have stopped with XMLs some time agoThey have stopped with XMLs some time ago

Thank youThank youThank you
@jarek000000@jarek000000@jarek000000
Sources:Sources:Sources:
Adam Warski 2017 - The Case against annotations
Tomer Gabel - Slaying sacred cows
From Spring Boot Apps to Functional Kotlin Nicholas Frankel
- plain java Pong server
-
https://sites.google.com/site/unclebobconsultingllc/blogs-by-robert-
martin/dependency-injection-inversion
https://www.youtube.com/watch?v=f6a78mCrSeE
https://github.com/javaFunAgain/ratpong
https://github.com/nee ect/nee

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