JdonFramework is a Domain Events framework that supports pub-sub asynchronous programming model.
No any message middlewares like Apache Kafka or RabbitMQ, you can directly command domain model doing something, and listen any domain events from domain model.
using JdonFramework, you can build your Domain Driven Design + CQRS + EventSourcing applications with asynchronous concurrency and higher throughput.
Jdonframework help you implement a clean and hexagonal architecture!
Domain-driven design (DDD) is an approach to developing software for complex needs by deeply connecting the implementation to an evolving model of the core business concepts,
DDD's servral concepts are the Heart and Soul of OOD:
Entities and Identity, Value Objects
Aggregate Root
Bounded context
CQRS: Command-query Responsibility Segregation, at its heart is a simple notion that you can use a different model to update information than the model you use to read information. domain events is the basice about CQRS and EventSourcing, it is all about what happened in aggregates, and means some changes happened in domain.
In CQRS, using domain events update query model; In Eventsourcing, append domain events into storage repository.
Give you a clean architecture!
Jdon introduces reactive and event-driven into domain, using jdon, a aggregate root can act as a mailbox(like scala's Actors) that is a asynchronous and non-blocking event-sending and event-recipient metaphor. Event is a better interactive way for aggregate root with each other, instead of directly exposing behavior and hold references to others. and it can better protect root entity's internal state not expose. and can safely update root's state in non-blocking way Single Writer Principle.
Jdon moves mutable state from database to memory, and uses Aggregate Root to guard it, traditional database's data operations (by SQL or JPA/ORM) not need any more, only need send a Command or Event to drive Aggregate Root to change its mutable state by its behaviours
@Model
public class AggregateRootA {
private int state = 100;
@OnCommand("CommandtoEventA")
public Object save(ParameterVO parameterVO) {
//update root's state in non-blocking single thread way (Single Writer)
this.state = parameterVO.getValue() + state;
}
}
Jdonframework work mode is Producer/Consumer, A producer emits to its Consumer by a asynchronous and non-blocking queue made by LMAX Disruptor's RingBuffer. such as:
@Send("CommandtoEventA") ---> @OnCommand("CommandtoEventA")
There are two kinds of Consumer in jdon:
@Send --> @OnCommand (1:1 Queue)
@Send --> @OnEvent (1:N topic)
Difference between 'OnCommand' and 'OnEvent' is:
When a event happend otherwhere comes in a aggregate root we regard this event as a command, and it will action a method annotated with @OnCommand, and in this method some events will happen. and they will action those methods annotated with @OnEvent.
full example: click here
Jdon can make your Domain Model as Actor(erlang/akka) concurrent model, no any lock. this is a transaction example about transferring money from one bank account to another:
@Model
public class BankAccount {
....
@OnCommand("depositCommand")
public Object deposit(TransferEvent transferEvent) {
int amount2 = amount + transferEvent.getValue();
if (amount2 > 1000) {
TransferEvent transferEventNew = new ResultEvent(
transferEvent.getId(), transferEvent.getValue(),
this.getId());
return domainEventProducer.failure(transferEventNew);
}
if (!(transferEvent instanceof WithdrawEvent)) {// first step
DepositEvent transferEventNew = new DepositEvent(
transferEvent.getId(), transferEvent.getValue(),
transferEvent.getNextId(), this.getId());
eventsourcesD.put(transferEventNew.getId(), transferEventNew);
return domainEventProducer.nextStep(transferEventNew);
}
WithdrawEvent de = (WithdrawEvent) transferEvent;
amount = amount + transferEvent.getValue();
TransferEvent transferEventNew = new ResultEvent(transferEvent.getId(),
transferEvent.getValue(), de.getPreId());
return domainEventProducer.finish(transferEventNew);
}
@OnCommand("withdrawCommand")
public Object withdraw(TransferEvent transferEvent) {
int amount2 = amount - transferEvent.getValue();
if (amount2 < 0) {
String rootId = (transferEvent instanceof DepositEvent) ? ((DepositEvent) transferEvent)
.getPreId() : this.getId();
TransferEvent transferEventNew = new ResultEvent(
transferEvent.getId(), transferEvent.getValue(), rootId);
return domainEventProducer.failure(transferEventNew);
}
if (!(transferEvent instanceof DepositEvent)) {// first step
WithdrawEvent transferEventNew = new WithdrawEvent(
transferEvent.getId(), transferEvent.getValue(),
transferEvent.getNextId(), this.getId());
eventsourcesW.put(transferEventNew.getId(), transferEventNew);
return domainEventProducer.nextStep(transferEventNew);
}
DepositEvent de = (DepositEvent) transferEvent;
amount = amount - transferEvent.getValue();
TransferEvent transferEventNew = new ResultEvent(transferEvent.getId(),
transferEvent.getValue(), de.getPreId());
return domainEventProducer.finish(transferEventNew);
}
@OnCommand("finishCommand")
public Object finish(TransferEvent transferEvent) {
if (eventsourcesW.containsKey(transferEvent.getId())){
eventsourcesW.remove(transferEvent.getId());
amount = amount - transferEvent.getValue();
}else if (eventsourcesD.containsKey(transferEvent.getId())){
eventsourcesD.remove(transferEvent.getId());
amount = amount + transferEvent.getValue();
}
return transferEvent;
}
@OnCommand("failureCommand")
public Object fail(TransferEvent transferEvent) {
eventsourcesD.remove(transferEvent.getId());
return transferEvent;
}
....
}
transfer money client code:
AppUtil appUtil = new AppUtil();
AccountService accountService = (AccountService) appUtil
.getComponentInstance("accountService");
BankAccount bankAccountA = accountService.getBankAccount("11", 100);
BankAccount bankAccountB = accountService.getBankAccount("22", 0);
DomainMessage res = accountService.transfer(bankAccountA, bankAccountB,
100);
DomainMessage res1 = (DomainMessage) res.getBlockEventResult();
DomainMessage result = (DomainMessage) res1.getBlockEventResult();
Object o = result.getBlockEventResult();// block until all transfer ok;
Assert.assertEquals(0, bankAccountA.getAmount());
Assert.assertEquals(100, bankAccountB.getAmount());
detail: click here
Apache Kafka supports Exactly-once delivery, Jdon Actor + Kafka can implement distributed transaction.
LMAX microservices distributed transaction
The Saga pattern is a preferable way of solving distributed transaction problems for a microservice-based architecture. However, it also introduces a new set of problems, such as how to atomically update the database and emit an event?
Jdonframework can atomically update database and emit an event by single-Writer pattern.
BPMN : execute this command!
aggregates: yes, Yes, task completed events!
Saga: I have accept domain events!.
Saga/process manager must hold every domain events from all aggregates, if there is any exception, it will rollback every step in this workflow，and send 'cancel' command to all aggregates to rollback.
Microservices to Workflows: The Evolution of Jet’s Order Management System
online documents : English: https://en.jdon.com/ Chinese: https://www.jdon.com/jdonframework/
In the "doc\english" directory there are all documents about how to use.
In the "doc\chinese" directory there are chinese documents about how to use.
In the "example" directory there are serveral examples that show how to use jdon, in these examples directory run 'mvn package' to get war file.
In the "JdonAccessory" directory there are struts1.x MVC and jdbc templates.
jivejdon is a discussion forum/blog/CMS platform powered by jdonframework
6.9 version.
apply jdonframework.jar to your project: MAVEN:
<dependency>
<groupId>org.jdon</groupId>
<artifactId>jdonframework</artifactId>
<version>6.9</version>
</dependency>
twiiter: @jdonframework
For bugs, questions and discussions please use the Github Issues.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
https://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.