Filter java模式_Java设计模式应用——过滤器模式

storm引擎计算出一批中间告警结果，会发送一条kafka消息给告警入库服务，告警入库服务接收到kafka消息后读取中间告警文件，经过一系列处理后把最终告警存入mysql中。

实际上，中间告警结果可能有重复告警、错误告警、无用告警，告警入库服务会过滤，压缩中间告警，把用户关心的告警存入数据库。过滤的步骤较多，并且客户关心的告警可能会随时变化，写死的告警过滤很快就无法满足应用场景，这种场景下使用过滤器模式则很好满足业务上的不确定性欲扩展性。

告警入库服务涉及消息过滤和告警过滤，下面我们以消息过滤器来讲一下过滤器模式。

1、消息过滤器接口

packagecom.coshaho.learn.filter;/***

* IMessageFilter.java Create on 2017年5月13日 上午12:43:56

*

* 类功能说明: 告警消息过滤器

*

* Copyright: Copyright(c) 2013

* Company: COSHAHO

* @Version 1.0

* @Author coshaho*/

public abstract class IMessageFilter implements Comparable{public intpriority()

{return 0;

}public abstract booleandoFilter(Message msg);public intcompareTo(IMessageFilter arg0)

{return priority() -arg0.priority();

}

}

2、时间过滤器

packagecom.coshaho.learn.filter;importorg.springframework.stereotype.Component;/***

* TimeFilter.java Create on 2017年5月13日 上午12:44:25

*

* 类功能说明: 时间过滤

*

* Copyright: Copyright(c) 2013

* Company: COSHAHO

* @Version 1.0

* @Author coshaho*/@Componentpublic class TimeFilter extendsIMessageFilter

{public intpriority()

{return 1;

}public booleandoFilter(Message msg)

{if(msg.getHour() < 8 || msg.getHour() > 17)

{

System.out.println("Time filter false, message is " +msg);return false;

}

System.out.println("Time filter true, message is " +msg);return true;

}

}

3、级别过滤器

packagecom.coshaho.learn.filter;importorg.springframework.stereotype.Component;/***

* ServerityFilter.java Create on 2017年5月13日 上午12:44:13

*

* 类功能说明: 级别过滤

*

* Copyright: Copyright(c) 2013

* Company: COSHAHO

* @Version 1.0

* @Author coshaho*/@Componentpublic class ServerityFilter extendsIMessageFilter

{public intpriority() {return 2;

}public booleandoFilter(Message msg) {if(msg.getSeverity() == 0)

{

System.out.println("Severity filter false, message is " +msg);return false;

}

System.out.println("Severity filter true, message is " +msg);return true;

}

}

4、类型过滤器

packagecom.coshaho.learn.filter;importorg.springframework.stereotype.Component;/***

* TypeFilter.java Create on 2017年5月13日 上午12:44:36

*

* 类功能说明: 类型过滤

*

* Copyright: Copyright(c) 2013

* Company: COSHAHO

* @Version 1.0

* @Author coshaho*/@Componentpublic class TypeFilter extendsIMessageFilter{public intpriority()

{return 3;

}public booleandoFilter(Message msg) {if(msg.getType() < 3)

{

System.out.println("Type filter false, message is " +msg);return false;

}

System.out.println("Type filter true, message is " +msg);return false;

}

}

5、消息监听服务

packagecom.coshaho.learn.filter;importjava.util.Collections;importjava.util.List;importorg.springframework.context.ApplicationContext;importorg.springframework.context.support.ClassPathXmlApplicationContext;importorg.springframework.stereotype.Component;/***

* MessageListener.java Create on 2017年5月13日 上午12:44:49

*

* 类功能说明: 告警消息监听

*

* Copyright: Copyright(c) 2013

* Company: COSHAHO

* @Version 1.0

* @Author coshaho*/@Componentpublic classMessageListener

{public static voidmain(String[] args)

{

@SuppressWarnings("resource")

ApplicationContext context= new ClassPathXmlApplicationContext("classpath:spring.xml");

MessageListener listener= (MessageListener)context.getBean("messageListener");

Message msg= newMessage();

msg.setHour(12);

msg.setName("coshaho");

msg.setType(5);

msg.setSeverity(3);

listener.listen(msg);

}public voidlisten(Message msg)

{

excute(msg);

}private booleanexcute(Message msg)

{

@SuppressWarnings("unchecked")

List filters = (List)SpringUtils.getBeansOfType(IMessageFilter.class);

Collections.sort(filters);for(IMessageFilter filter : filters)

{if(!filter.doFilter(msg))

{return false;

}

}return true;

}

}

6、Spring工具类

packagecom.coshaho.learn.filter;importjava.util.ArrayList;importjava.util.List;importjava.util.Map;importorg.springframework.beans.BeansException;importorg.springframework.context.ApplicationContext;importorg.springframework.context.ApplicationContextAware;importorg.springframework.stereotype.Service;

@Servicepublic class SpringUtils implementsApplicationContextAware

{private staticApplicationContext context;public voidsetApplicationContext(ApplicationContext context)throwsBeansException

{

SpringUtils.context=context;

}

@SuppressWarnings({"rawtypes", "unchecked"})public staticList getBeansOfType(Class clazz)

{

Map map=context.getBeansOfType(clazz);return newArrayList(map.values());

}

}

7、消息类

packagecom.coshaho.learn.filter;/***

* Message.java Create on 2017年5月13日 上午12:43:37

*

* 类功能说明: 告警消息

*

* Copyright: Copyright(c) 2013

* Company: COSHAHO

* @Version 1.0

* @Author coshaho*/

public classMessage

{privateString name;private inthour;private inttype;private intseverity;publicString getName() {returnname;

}public voidsetName(String name) {this.name =name;

}public intgetHour() {returnhour;

}public void setHour(inthour) {this.hour =hour;

}public intgetType() {returntype;

}public void setType(inttype) {this.type =type;

}public intgetSeverity() {returnseverity;

}public void setSeverity(intseverity) {this.severity =severity;

}

@OverridepublicString toString() {return "Message [name=" + name + ", hour=" + hour + ", type=" +type+ ", severity=" + severity + "]";

}

}

可以看到，过滤器模式可以很方便的扩展过滤业务。