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Cleanup Java #1

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64a3139
Refactor and clean up some code
wilvdb May 2, 2020
5284899
Add getter and setters + private constructors
wilvdb May 3, 2020
b74f578
Review generics
wilvdb May 8, 2020
db2fa14
Remove lombok
wilvdb May 9, 2020
8f6c0bb
Step 2 - add getter and setters
wilvdb May 9, 2020
f662d05
Step 3 - add getter and setters
wilvdb May 9, 2020
18d0171
Step 3 - fix test
wilvdb May 9, 2020
9b2f7a2
Step 4 - add getter and setter
wilvdb May 9, 2020
5cd75f4
Step 5 - add getter and setter
wilvdb May 9, 2020
7ae25a2
Step 6 - add getter and setter
wilvdb May 9, 2020
3790e6c
Step 6 - refactor generic components
wilvdb May 9, 2020
15e7593
Step 5 - refactor generic components
wilvdb May 9, 2020
a7b76a8
Step 4 - refactor generic components
wilvdb May 9, 2020
f3d26ce
Remove singleton
wilvdb May 10, 2020
80d5a2b
Replace ifthenelse code by registry and lambda
wilvdb Jun 9, 2020
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6 changes: 6 additions & 0 deletions Step07/app/build.gradle
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Expand Up @@ -16,5 +16,11 @@ repositories {
dependencies {
implementation 'org.springframework.boot:spring-boot-starter'
runtimeOnly 'org.springframework.boot:spring-boot-devtools'
compileOnly 'org.projectlombok:lombok:1.18.12'
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@cpontet cpontet May 20, 2020

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Because this code is a workshop, and because not everyone is familiar with lombok, I wanted to use vanilla java code and not carry extra dependencies doing black magic. I admit though that lombok is a good library.

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@wilvdb wilvdb Jun 9, 2020

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I used it when I started to modify the code, but it has been removed since.

annotationProcessor 'org.projectlombok:lombok:1.18.12'

testCompileOnly 'org.projectlombok:lombok:1.18.12'
testAnnotationProcessor 'org.projectlombok:lombok:1.18.12'

testImplementation 'org.springframework.boot:spring-boot-starter-test'
}
6 changes: 3 additions & 3 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/core/AggregateRoot.java
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Expand Up @@ -32,8 +32,8 @@ public final Iterable<? extends Event> getUncommittedChanges() {

public final void loadFromHistory(Iterable<? extends Event> history) {
for (Event e : history) {
if(version + 1 == e.version) {
version = e.version;
if(version + 1 == e.getVersion()) {
version = e.getVersion();
}
applyChange(e, false);
}
Expand All @@ -48,7 +48,7 @@ private void applyChange(Event event, boolean isNew) {

if (isNew) {
version++;
event.version = version;
event.setVersion(version);
changes.add(event);
}
}
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13 changes: 10 additions & 3 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/core/Command.java
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@@ -1,11 +1,18 @@
package net.agilepartner.workshops.cqrs.core;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.Setter;

import java.util.UUID;

@Getter
@Setter(AccessLevel.PROTECTED)
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@cpontet cpontet May 20, 2020

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Ouuuuhhh black magic

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@wilvdb wilvdb Jun 9, 2020

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Black magic has been removed.

public abstract class Command implements Message {
public UUID id;
public UUID aggregateId;

private static final long serialVersionUID = -840035726759327475L;

private UUID id;
private UUID aggregateId;


}
13 changes: 10 additions & 3 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/core/Event.java
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@@ -1,10 +1,17 @@
package net.agilepartner.workshops.cqrs.core;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.Setter;

import java.util.UUID;

@Getter
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@cpontet cpontet May 20, 2020

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More black magic

@Setter
public abstract class Event implements Message {
public UUID aggregateId;
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@cpontet cpontet May 20, 2020

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I understand it seems counter-intuitive to have public fields, but most likely the events will be serialized, and there is no real need for encapsulation here, since events (and command for that matter) are mainly data containers, and have no logic.
Therefore, I go for simplicity and don't need getters and setters that just add syntactic noise here... using the black magic of lombok

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@wilvdb wilvdb Jun 9, 2020

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Sure, it's counter-intuitive. And in case field are not encapsulated, the temptation is use something like lombok.

public int version;

private static final long serialVersionUID = 8922791526755347386L;

private UUID aggregateId;
private int version;

}
4 changes: 2 additions & 2 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/core/Repository.java
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Expand Up @@ -3,6 +3,6 @@
import java.util.UUID;

public interface Repository<T extends AggregateRoot> {
public T getById(UUID aggregateId);
public void save(T aggregate);
T getById(UUID aggregateId);
void save(T aggregate);
}
10 changes: 10 additions & 0 deletions ...n/java/net/agilepartner/workshops/cqrs/core/infrastructure/UnsupportedEventException.java
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@@ -0,0 +1,10 @@
package net.agilepartner.workshops.cqrs.core.infrastructure;

import net.agilepartner.workshops.cqrs.core.Event;

public class UnsupportedEventException extends RuntimeException {

public UnsupportedEventException(Class< ? extends Event> eventType) {
super("Unsupported event " + eventType.getSimpleName());
}
}
2 changes: 1 addition & 1 deletion ...n/java/net/agilepartner/workshops/cqrs/core/infrastructure/memory/InMemoryEventStore.java
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Expand Up @@ -24,7 +24,7 @@ public void save(UUID aggregateId, Iterable<? extends Event> newEvents, int expe

if (events.containsKey(aggregateId)) {
existingEvents = events.get(aggregateId);
currentVersion = existingEvents.get(existingEvents.size() - 1).version;
currentVersion = existingEvents.get(existingEvents.size() - 1).getVersion();
} else {
events.put(aggregateId, existingEvents);
}
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12 changes: 9 additions & 3 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/CheckInventoryItemIn.java
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Expand Up @@ -2,16 +2,22 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Command;

@Getter
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class CheckInventoryItemIn extends Command {
private static final long serialVersionUID = 1L;
public int quantity;

private int quantity;

public static CheckInventoryItemIn create(UUID aggregateId, int quantity) {
CheckInventoryItemIn cmd = new CheckInventoryItemIn();
cmd.id = UUID.randomUUID();
cmd.aggregateId = aggregateId;
cmd.setId(UUID.randomUUID());
cmd.setAggregateId(aggregateId);
cmd.quantity = quantity;

return cmd;
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4 changes: 2 additions & 2 deletions ...app/src/main/java/net/agilepartner/workshops/cqrs/domain/CheckInventoryItemInHandler.java
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Expand Up @@ -12,8 +12,8 @@ public CheckInventoryItemInHandler(Repository<InventoryItem> repository) {

@Override
public void handle(CheckInventoryItemIn command) throws InventoryItemDeactivatedException {
InventoryItem item = repository.getById(command.aggregateId);
item.checkIn(command.quantity);
InventoryItem item = repository.getById(command.getAggregateId());
item.checkIn(command.getQuantity());
repository.save(item);
}
}
12 changes: 9 additions & 3 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/CheckInventoryItemOut.java
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Expand Up @@ -2,16 +2,22 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Command;

@Getter
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class CheckInventoryItemOut extends Command {
private static final long serialVersionUID = 2660471147867347530L;
public int quantity;

private int quantity;

public static CheckInventoryItemOut create(UUID aggregateId, int quantity) {
CheckInventoryItemOut cmd = new CheckInventoryItemOut();
cmd.id = UUID.randomUUID();
cmd.aggregateId = aggregateId;
cmd.setId(UUID.randomUUID());
cmd.setAggregateId(aggregateId);
cmd.quantity = quantity;

return cmd;
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4 changes: 2 additions & 2 deletions ...pp/src/main/java/net/agilepartner/workshops/cqrs/domain/CheckInventoryItemOutHandler.java
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Expand Up @@ -12,8 +12,8 @@ public CheckInventoryItemOutHandler(Repository<InventoryItem> repository) {

@Override
public void handle(CheckInventoryItemOut command) throws NotEnoughStockException, InventoryItemDeactivatedException {
InventoryItem item = repository.getById(command.aggregateId);
item.checkOut(command.quantity);
InventoryItem item = repository.getById(command.getAggregateId());
item.checkOut(command.getQuantity());
repository.save(item);
}
}
15 changes: 10 additions & 5 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/CreateInventoryItem.java
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Expand Up @@ -2,19 +2,24 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Command;

@Getter
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class CreateInventoryItem extends Command {

private static final long serialVersionUID = 1L;
public String name;
public int initialQuantity;

private String name;
private int initialQuantity;

public static CreateInventoryItem create(String name, int initialQuantity) {
CreateInventoryItem cmd = new CreateInventoryItem();
cmd.id = UUID.randomUUID();
cmd.aggregateId = UUID.randomUUID();
cmd.setId(UUID.randomUUID());
cmd.setAggregateId(UUID.randomUUID());
cmd.name = name;
cmd.initialQuantity = initialQuantity;

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2 changes: 1 addition & 1 deletion .../app/src/main/java/net/agilepartner/workshops/cqrs/domain/CreateInventoryItemHandler.java
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Expand Up @@ -12,7 +12,7 @@ public CreateInventoryItemHandler(Repository<InventoryItem> repository) {

@Override
public void handle(CreateInventoryItem command) {
InventoryItem item = InventoryItem.create(command.aggregateId, command.name, command.initialQuantity);
InventoryItem item = InventoryItem.create(command.getAggregateId(), command.getName(), command.getInitialQuantity());
repository.save(item);
}
}
7 changes: 5 additions & 2 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/DeactivateInventoryItem.java
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Expand Up @@ -2,16 +2,19 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Command;

@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class DeactivateInventoryItem extends Command {

private static final long serialVersionUID = 1L;

public static DeactivateInventoryItem create(UUID aggregateId) {
DeactivateInventoryItem cmd = new DeactivateInventoryItem();
cmd.id = UUID.randomUUID();
cmd.aggregateId = aggregateId;
cmd.setId(UUID.randomUUID());
cmd.setAggregateId(aggregateId);

return cmd;
}
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2 changes: 1 addition & 1 deletion .../src/main/java/net/agilepartner/workshops/cqrs/domain/DeactivateInventoryItemHandler.java
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Expand Up @@ -12,7 +12,7 @@ public DeactivateInventoryItemHandler(Repository<InventoryItem> repository) {

@Override
public void handle(DeactivateInventoryItem command) {
InventoryItem item = repository.getById(command.aggregateId);
InventoryItem item = repository.getById(command.getAggregateId());
item.deactivate();;
repository.save(item);
}
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10 changes: 5 additions & 5 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/InventoryItem.java
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Expand Up @@ -63,18 +63,18 @@ private void checkActivated() throws InventoryItemDeactivatedException {
protected <T extends Event> void apply(T event) {
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@cpontet cpontet May 20, 2020

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Actually, this is exactly what we want to avoid by having the "ugly" reflection code in the AggregateRoot base class.

I want to avoid the if-then-else like the plague and I'd much rather stay with nice, clean, and small apply methods that respect the Single Responsibility Principle instead.

I agree that reflection is not the most efficient and clean way to implement that. There are cleaner ways to implement the AggregateRoot base class to avoid reflection, using a more functional approach for example. But this code is for a workshop and I personally prefer focussing on a clean domain than the plumbing code.

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@wilvdb wilvdb Jun 9, 2020

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For this point, I'm totally agree it is not ideal. I'm just looking for a better solution.
I propose to implement it as bellow:

public abstract class AggregateRoot {
    protected Map<Class<? extends Event>, Consumer<? extends Event>> eventsConsumer = new HashMap<>();

    protected AggregateRoot(UUID id) {
        registerEventsConsumer();
        this.id = id;
    }

    protected abstract void registerEventsConsumer();
}

class InventoryItem extends AggregateRoot {
@Override
    protected void registerEventsConsumer() {
        eventsConsumer.put(InventoryItemCreated.class, (Consumer<InventoryItemCreated>) this::apply);
        eventsConsumer.put(InventoryItemRenamed.class, (Consumer<InventoryItemRenamed>) this::apply);
        eventsConsumer.put(InventoryItemCheckedIn.class, (Consumer<InventoryItemCheckedIn>) this::apply);
        eventsConsumer.put(InventoryItemCheckedOut.class, (Consumer<InventoryItemCheckedOut>) this::apply);
        eventsConsumer.put(InventoryItemDeactivated.class, (Consumer<InventoryItemDeactivated>) this::apply);
    }

private void apply(InventoryItemCreated event) {
        this.name = event.getName();
        this.stock = event.getQuantity();
        this.active = true;
    }
}

Single Responsibility Principle is respected, and there is no more ugly code.

if (event instanceof InventoryItemCreated) {
InventoryItemCreated evt = (InventoryItemCreated) event;
this.name = evt.name;
this.stock = evt.quantity;
this.name = evt.getName();
this.stock = evt.getQuantity();
this.active = true;
} else if (event instanceof InventoryItemRenamed) {
InventoryItemRenamed evt = (InventoryItemRenamed) event;
this.name = evt.name;
this.name = evt.getName();
} else if (event instanceof InventoryItemCheckedIn) {
InventoryItemCheckedIn evt = (InventoryItemCheckedIn) event;
this.stock += evt.quantity;
this.stock += evt.getQuantity();
} else if (event instanceof InventoryItemCheckedOut) {
InventoryItemCheckedOut evt = (InventoryItemCheckedOut) event;
this.stock -= evt.quantity;
this.stock -= evt.getQuantity();
} else if (event instanceof InventoryItemDeactivated) {
this.active = false;
} else {
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10 changes: 8 additions & 2 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/InventoryItemCheckedIn.java
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Expand Up @@ -2,15 +2,21 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Event;

@Getter
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class InventoryItemCheckedIn extends Event {
private static final long serialVersionUID = -8744398303363497614L;
public int quantity;

private int quantity;

public static InventoryItemCheckedIn create(UUID aggregateId, int quantity) {
InventoryItemCheckedIn evt = new InventoryItemCheckedIn();
evt.aggregateId = aggregateId;
evt.setAggregateId(aggregateId);
evt.quantity = quantity;
return evt;
}
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9 changes: 7 additions & 2 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/InventoryItemCheckedOut.java
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Expand Up @@ -2,15 +2,20 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Event;

@Getter
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class InventoryItemCheckedOut extends Event {
private static final long serialVersionUID = 1L;
public int quantity;
private int quantity;

public static InventoryItemCheckedOut create(UUID aggregateId, int quantity) {
InventoryItemCheckedOut evt = new InventoryItemCheckedOut();
evt.aggregateId = aggregateId;
evt.setAggregateId(aggregateId);
evt.quantity = quantity;
return evt;
}
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12 changes: 9 additions & 3 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/InventoryItemCreated.java
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Expand Up @@ -2,16 +2,22 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Event;

@Getter
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class InventoryItemCreated extends Event {
private static final long serialVersionUID = -5604800934233512172L;
public String name;
public int quantity;

private String name;
private int quantity;

public static InventoryItemCreated create(UUID aggregateId, String name, int quantity) {
InventoryItemCreated evt = new InventoryItemCreated();
evt.aggregateId = aggregateId;
evt.setAggregateId(aggregateId);
evt.name = name;
evt.quantity = quantity;
return evt;
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5 changes: 4 additions & 1 deletion ...07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/InventoryItemDeactivated.java
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Expand Up @@ -2,15 +2,18 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Event;

@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class InventoryItemDeactivated extends Event {

private static final long serialVersionUID = 1L;

public static InventoryItemDeactivated create(UUID aggregateId) {
InventoryItemDeactivated evt = new InventoryItemDeactivated();
evt.aggregateId = aggregateId;
evt.setAggregateId(aggregateId);
return evt;
}
}
10 changes: 8 additions & 2 deletions Step07/app/src/main/java/net/agilepartner/workshops/cqrs/domain/InventoryItemRenamed.java
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Expand Up @@ -2,15 +2,21 @@

import java.util.UUID;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import net.agilepartner.workshops.cqrs.core.Event;

@Getter
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class InventoryItemRenamed extends Event {
private static final long serialVersionUID = 1L;
public String name;

private String name;

public static InventoryItemRenamed create(UUID aggregateId, String name) {
InventoryItemRenamed evt = new InventoryItemRenamed();
evt.aggregateId = aggregateId;
evt.setAggregateId(aggregateId);
evt.name = name;
return evt;
}
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