CQRS框架:AxonFramework 之 Hello World

Command Query Responsibility Segregation,CQRS 这个架构好象最近博客园里讨论得比较多,有几篇园友的文章很有深度,推荐阅读:

CQRS架构简介

浅谈命令查询职责分离(CQRS)模式

DDD CQRS架构和传统架构的优缺点比较

比较有趣的是,以往一断谈及架构思路、OO这些,往往都是java大佬们的专长,而CQRS这个话题,好象.NET占了上风。园友汤雪华ENODE开源大作,在github上人气也很旺。

于是,我逆向思路搜索了下java的类似项目,果然有一个AxonFramework,甚至还有一个专门的网站。按文档上的介绍,弄了一个hello world,记录一下:

CRQS是基于事件驱动的,其主要架构并不复杂,见下图:

简单来讲,对数据库的修改操作,UI层只管发送各种命令(Command),触发事件(Event),然后由EventHandler去异步处理,最终写入master DB,对于数据库的查询,则查询slave DB(注:这里的master db, slave db只是一个逻辑上的区分,可以是真正的主-从库,也可以都是一个库)。 这样的架构,很容易实现读写分离,也易于大型项目的扩展。

项目结构:

package的名称上大概就能看出用途:

command包定义各种命令,

event包定义各种事件,

handler包定义事件处理逻辑,

model包相当于领域模型

最外层的ToDOItemRunner相当于应用程序入口。

gradle依赖项:

group 'yjmyzz'
version '1.0'

apply plugin: 'java'
apply plugin: 'application'

sourceCompatibility = 1.8

repositories {
    mavenLocal()
    maven {
        url 'http://maven.oschina.net/content/groups/public/'
    }
    mavenCentral()
}

dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
    compile "org.axonframework:axon:2.4.3"
    compile "org.axonframework:axon-core:2.4.3"
    compile "org.axonframework:axon-test:2.4.3"
    compile 'org.springframework:spring-core:4.2.3.RELEASE'
    compile 'org.springframework:spring-beans:4.2.3.RELEASE'
    compile 'org.springframework:spring-context:4.2.3.RELEASE'
    compile 'org.springframework:spring-context-support:4.2.3.RELEASE'
    compile 'org.springframework:spring-aop:4.2.3.RELEASE'
    compile 'org.springframework:spring-test:4.2.3.RELEASE'
    compile 'org.apache.logging.log4j:log4j-slf4j-impl:2.5'
    compile 'org.apache.logging.log4j:log4j-core:2.5'
    compile 'javax.persistence:persistence-api:2.1'
}

mainClassName='demo.axon.ToDoItemRunner'

command命令:

这里我们假设了二个命令:创建命令、完成命令

CreateToDoItemCommand

package demo.axon.command;

import org.axonframework.commandhandling.annotation.TargetAggregateIdentifier;

public class CreateToDoItemCommand {

    @TargetAggregateIdentifier
    private final String todoId;
    private final String description;

    public CreateToDoItemCommand(String todoId, String description) {
        this.todoId = todoId;
        this.description = description;
    }

    public String getTodoId() {
        return todoId;
    }

    public String getDescription() {
        return description;
    }
}

MarkCompletedCommand

package demo.axon.command;

import org.axonframework.commandhandling.annotation.TargetAggregateIdentifier;

public class MarkCompletedCommand {

    @TargetAggregateIdentifier
    private final String todoId;

    public MarkCompletedCommand(String todoId) {
        this.todoId = todoId;
    }

    public String getTodoId() {
        return todoId;
    }
}

Event事件:

ToDoItemCreatedEvent

package demo.axon.event;

public class ToDoItemCreatedEvent {

    private final String todoId;
    private final String description;

    public ToDoItemCreatedEvent(String todoId, String description) {
        this.todoId = todoId;
        this.description = description;
    }

    public String getTodoId() {
        return todoId;
    }

    public String getDescription() {
        return description;
    }
}
ToDoItemCompletedEvent
package demo.axon.event;

public class ToDoItemCompletedEvent {

    private final String todoId;

    public ToDoItemCompletedEvent(String todoId) {
        this.todoId = todoId;
    }

    public String getTodoId() {
        return todoId;
    }
}

EventHandler事件处理

package demo.axon.handler;

import demo.axon.event.ToDoItemCompletedEvent;
import demo.axon.event.ToDoItemCreatedEvent;
import org.axonframework.eventhandling.annotation.EventHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ToDoEventHandler {

    Logger logger = LoggerFactory.getLogger(ToDoEventHandler.class);

    @EventHandler
    public void handle(ToDoItemCreatedEvent event) {
        logger.info("We've got something to do: " + event.getDescription() + " (" + event.getTodoId() + ")");
    }

    @EventHandler
    public void handle(ToDoItemCompletedEvent event) {
        logger.info("We've completed a task: " + event.getTodoId());
    }
}

上面的代码只是演示,将事件信息输出而已,真实应用中,这里可以完成对db的更新操作。 

领域模型model

package demo.axon.model;

import demo.axon.command.CreateToDoItemCommand;
import demo.axon.command.MarkCompletedCommand;
import demo.axon.event.ToDoItemCompletedEvent;
import demo.axon.event.ToDoItemCreatedEvent;
import org.axonframework.commandhandling.annotation.CommandHandler;
import org.axonframework.eventhandling.annotation.EventHandler;
import org.axonframework.eventsourcing.annotation.AbstractAnnotatedAggregateRoot;
import org.axonframework.eventsourcing.annotation.AggregateIdentifier;

public class ToDoItem extends AbstractAnnotatedAggregateRoot {

    @AggregateIdentifier
    private String id;

    public ToDoItem() {
    }

    @CommandHandler
    public ToDoItem(CreateToDoItemCommand command) {
        apply(new ToDoItemCreatedEvent(command.getTodoId(), command.getDescription()));
    }

    @EventHandler
    public void on(ToDoItemCreatedEvent event) {
        this.id = event.getTodoId();
    }

    @CommandHandler
    public void markCompleted(MarkCompletedCommand command) {
        apply(new ToDoItemCompletedEvent(id));
    }
}

然后让Spring将这些东西串在一起,配置文件如下:

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4        xmlns:axon="http://www.axonframework.org/schema/core"
 5        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
 6                            http://www.axonframework.org/schema/core http://www.axonframework.org/schema/axon-core-2.0.xsd">
 7 
 8     <axon:command-bus id="commandBus"/>
 9     <axon:event-bus id="eventBus"/>
10 
11     <axon:event-sourcing-repository id="toDoRepository"
12                                     aggregate-type="demo.axon.model.ToDoItem"/>
13 
14     <axon:aggregate-command-handler id="toDoItemHandler"
15                                     aggregate-type="demo.axon.model.ToDoItem"
16                                     repository="toDoRepository"
17                                     command-bus="commandBus"/>
18 
19     <axon:filesystem-event-store id="eventStore" base-dir="events"/>
20 
21     <axon:annotation-config />
22 
23     <bean class="demo.axon.handler.ToDoEventHandler"/>
24 
25     <bean class="org.axonframework.commandhandling.gateway.CommandGatewayFactoryBean">
26         <property name="commandBus" ref="commandBus"/>
27     </bean>
28 
29 </beans>

最后,提供一个舞台,让整个应用run起来:

package demo.axon;

import demo.axon.command.CreateToDoItemCommand;
import demo.axon.command.MarkCompletedCommand;
import org.axonframework.commandhandling.gateway.CommandGateway;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.util.UUID;

public class ToDoItemRunner {

    private CommandGateway commandGateway;

    public ToDoItemRunner(CommandGateway commandGateway) {
        this.commandGateway = commandGateway;
    }

    public static void main(String[] args) {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("sampleContext.xml");
        ToDoItemRunner runner = new ToDoItemRunner(applicationContext.getBean(CommandGateway.class));
        runner.run();
    }

    private void run() {
        final String itemId = UUID.randomUUID().toString();
        commandGateway.send(new CreateToDoItemCommand(itemId, "Need to do this"));
        commandGateway.send(new MarkCompletedCommand(itemId));
    }
}

输出结果:

12:01:36,113 <demo.axon.handler.ToDoEventHandler>  INFO [main]: We've got something to do: Need to do this (3126f293-67fd-4bb7-b152-069acba775b6)
12:01:36,114 <org.axonframework.commandhandling.callbacks.LoggingCallback>  INFO [main]: Command executed successfully: demo.axon.command.CreateToDoItemCommand
12:01:36,205 <demo.axon.handler.ToDoEventHandler>  INFO [main]: We've completed a task: 3126f293-67fd-4bb7-b152-069acba775b6
12:01:36,206 <org.axonframework.commandhandling.callbacks.LoggingCallback>  INFO [main]: Command executed successfully: demo.axon.command.MarkCompletedCommand

axon框架测试也很容易:

package test.demo.axon;

import demo.axon.command.CreateToDoItemCommand;
import demo.axon.command.MarkCompletedCommand;
import demo.axon.event.ToDoItemCompletedEvent;
import demo.axon.event.ToDoItemCreatedEvent;
import demo.axon.model.ToDoItem;
import org.axonframework.test.FixtureConfiguration;
import org.axonframework.test.Fixtures;
import org.junit.Before;
import org.junit.Test;

public class ToDoItemTest {

    private FixtureConfiguration fixture;

    @Before
    public void setUp() throws Exception {
        fixture = Fixtures.newGivenWhenThenFixture(ToDoItem.class);
    }

    @Test
    public void testCreateToDoItem() throws Exception {
        fixture.given()
                .when(new CreateToDoItemCommand("todo1", "need to implement the aggregate"))
                .expectEvents(new ToDoItemCreatedEvent("todo1", "need to implement the aggregate"));
    }

    @Test
    public void testMarkToDoItemAsCompleted() throws Exception {
        fixture.given(new ToDoItemCreatedEvent("todo1", "need to implement the aggregate"))
                .when(new MarkCompletedCommand("todo1"))
                .expectEvents(new ToDoItemCompletedEvent("todo1"));
    }

}

given/when/expectEvents的意思是,给(given)一个事件,然后当(when)某个命令被调用时,期待(expectEvents)某个事件被触发。

最后 github上还有一个比较复杂的示例项目:https://github.com/AxonFramework/Axon-trader,想深入了解的可以研究下

本文参与腾讯云自媒体分享计划,欢迎正在阅读的你也加入,一起分享。

发表于

我来说两句

0 条评论
登录 后参与评论

相关文章

来自专栏乐沙弥的世界

X86 DBCA, NETCA GIVE JAVA HOTSPOT ERROR IF ON X86_64 HARDWARE

    在使用DBCA命令创建新的数据库时,DBCA命令无法启动。运行的环境是宿主机64bit+AMD cpu, 而客户机为Linux 32bit + Grid...

10420
来自专栏Objective-C

iOS-安装和使用 CocoaPods

55970
来自专栏耕耘实录

找回win7桌面IE图标我有绝招

现在很多同学都用了微软的新一代操作系统Windows7,都为Windows7的华丽界面及更人性化得操作所深深吸引,但是由于我们大多数同学都习惯了原来的Windo...

37250
来自专栏微信音视频小程序

教你1天搭建自己的“微视”

A simple iOS Application project is shown below to illustrate how to configure S...

1.1K50
来自专栏杨建荣的学习笔记

由一条日志警告所做的调优分析(r3笔记第40天)

这个案例发生有段时间了,但是今天无意中看到当时的邮件,感觉还是收益匪浅,看来还是细节决定成败啊。从一些日志或trace 文件中的警告信息中我们可以发掘出潜在的问...

37730
来自专栏阿杜的世界

Spring Boot with Redis

Spring Boot是为了简化Spring开发而生,从Spring 3.x开始,Spring社区的发展方向就是弱化xml配置文件而加大注解的戏份。最近召开的S...

10920
来自专栏Android中高级开发

Android开发之漫漫长途 IX——彻底掌握Binder

该文章是一个系列文章,是本人在Android开发的漫漫长途上的一点感想和记录,我会尽量按照先易后难的顺序进行编写该系列。该系列引用了《Android开发艺术探索...

12420
来自专栏光变

Gradle Unsupported Method 'provided'

8810
来自专栏一个会写诗的程序员的博客

Spring Boot 集成 WebFlux 开发 Reactive Web 应用Spring Boot 集成 WebFlux 开发 Reactive Web 应用

IBM的研究称,整个人类文明所获得的全部数据中,有90%是过去两年内产生的。在此背景下,包括NoSQL,Hadoop, Spark, Storm, Kylin在...

16320
来自专栏数据和云

实践真知:使用ASM和文件系统的数据库在AIO上有何不同?

张大朋(Lunar)Oracle 资深技术专家 Lunar 拥有超过十年的 ORACLE SUPPORT 从业经验,曾经服务于ORACLE ACS部门,现就职...

30840

扫码关注云+社区

领取腾讯云代金券