EventBus 不是通用的消息系统，也不是用来做进程间的通信的，而是在进程内，用于解耦两段直接调用的业务逻辑；
1、代码结构
- event：eventbus中流转的事件（消息），包结构按照业务模块在细分(比如应用部署模块就是deployment)；
- subscriber：消费者，和event 是一一对应的，一个event 对应一个消费者，包结构按照业务模块在细分(比如应用部署模块就是deployment)；
- poster：生产者，这边把生产者单独出来是为了收敛入口，这样可以方便的知道有哪些地方在生产消息，按照业务模块分为不同的类(因为生产消息的功能比较单薄)；
2、代码实现
在applicationContext.xml 中定义好EventBus
asyncEventBus
<
bean
id
=
"taskExecutor"
class
=
"org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor"
lazy-init
=
"true"
>
<
property
name
=
"corePoolSize"
value
=
"10"
/>
<
property
name
=
"maxPoolSize"
value
=
"50"
/>
<
property
name
=
"queueCapacity"
value
=
"10000"
/>
<
property
name
=
"keepAliveSeconds"
value
=
"300"
/>
<
property
name
=
"rejectedExecutionHandler"
>
<
bean
class
=
"java.util.concurrent.ThreadPoolExecutor$CallerRunsPolicy"
/>
</
property
>
</
bean
>
<
bean
id
=
"asyncEventBus"
class
=
"com.google.common.eventbus.AsyncEventBus"
>
<
constructor-arg
name
=
"executor"
ref
=
"taskExecutor"
/>
</
bean
>
|
2.1、标准化subscriber
所有的subscriber都要实现 BaseSubscriber这个 interface
BaseSubscriber
public
interface
BaseSubscriber<E> {
/**
* event 处理逻辑入口
**/
void
subscribe(E event);
}
|
所有的subscriber在类上加上EventBusRegister 这个annotation
EventBusRegister
@Target
({ElementType.TYPE})
@Retention
(RetentionPolicy.RUNTIME)
@Documented
public
@interface
EventBusRegister {
}
|
实现EventBusAdapter用于自动注册subscriber
EventBusAdapter
@Component
public
class
EventBusAdapter
implements
ApplicationContextAware, InitializingBean {
@Autowired
private
AsyncEventBus asyncEventBus;
private
ApplicationContext applicationContext;
@Override
public
void
afterPropertiesSet()
throws
Exception {
this
.applicationContext.getBeansWithAnnotation(EventBusRegister.
class
).forEach((name, bean) -> {
asyncEventBus.register(bean);
});
}
@Override
public
void
setApplicationContext(ApplicationContext applicationContext)
throws
BeansException {
this
.applicationContext = applicationContext;
}
}
|
举个例子
BuildUpdateSubscriber
@Component
@EventBusRegister
public
class
BuildUpdateSubscriber
implements
BaseSubscriber<BuildUpdateEvent> {
@Autowired
private
BuildService buildService;
@Subscribe
@Override
public
void
subscribe(BuildUpdateEvent event) {
switch
(event.getEventType()) {
case
BUILD_CONNECTED:
List<BuildVo> buildVos = (List<BuildVo>) event.getData();
buildService.addBuildVosAndTriggerConnectEvent(buildVos);
break
;
case
BUILD_ADD:
BuildVo addedBuildVo = (BuildVo) event.getData();
buildService.addBuildVoAndTriggerClientEvent(addedBuildVo);
break
;
case
BUILD_MODIFY:
BuildVo modifiedBuildVo = (BuildVo) event.getData();
buildService.modifyBuildVoAndTriggerEvent(modifiedBuildVo);
break
;
case
BUILD_DELETE:
BuildVo deletedBuildVo = (BuildVo) event.getData();
buildService.deleteBuildVoAndTriggerClientEvent(deletedBuildVo);
break
;
default
:
// ignore
break
;
}
}
}
|
3、代码实现改进
前面通过规范代码的包结构、加了一些trick使得我们可以方便的使用eventbus解耦我们的业务逻辑，但是有时候我们需要的bean被注册 的前后做一些业务逻辑，所以我们在bean 被注册到eventbus前后加了两个hook：AfterRegisterProcessor、BeforeRegisterProcessor；实现这两个interface并且实现对于的方法，会在bean 被注册前后被调用
bean 注册到eventbus前的hook
BeforeRegisterProcessor
public
interface
BeforeRegisterProcessor {
void
beforeRegister();
}
|
bean 注册到eventbus后的hook
AfterRegisterProcessor
public
interface
AfterRegisterProcessor {
void
afterRegister();
}
|
实现：保证在 client.watch 之前，注册已经完成，这样watch产生的消息就能够保证被成功消费
GlueService
@Service
public
class
GlueService
implements
AfterRegisterProcessor {
@Autowired
private
PodListener podListener;
@Autowired
private
RouteListener routerListener;
@Autowired
private
BuildListener buildListener;
@Autowired
private
DeploymentListener deploymentListener;
@Autowired
private
OpenShiftClient openShiftClient;
@Override
public
void
afterRegister() {
IClient client = openShiftClient.getClient();
podWatch = client.watch(podListener, ResourceKind.POD);
routeWatch = client.watch(routerListener, ResourceKind.ROUTE);
buildWatch = client.watch(buildListener, ResourceKind.BUILD);
deploymentWatch = client.watch(deploymentListener, ResourceKind.REPLICATION_CONTROLLER);
}
}
|