Esper学习之十四：Pattern（一）

标签：cep   esper   数据   开源   

       今天这篇主要讲讲一些基础知识以便领大家入门，具体的语法下篇会有详细说明。

1. Pattern Atoms and Pattern operators
Pattern是通过原子事件和操作符组合在一起构成模板。原子事件有3类，操作符有4类，具体如下：

原子事件：
1). 普通事件：包括POJO，Map，Array，XML
2). 时间事件：包括间隔n个时间单位、crontab
3). 自定义插件：用于观察特定事件的发生

操作符：
1). 重复操作符：every, every-distinct, [num] and until
2). 逻辑操作符：and, or, not
3). 顺序操作符：->（Followed by）
4). 事件生命周期操作符：timer:within, timer:withinmax, while-expression, 自定义插件

关于操作符，自然会有优先级，具体如下：

上面的内容各位可以先有个印象，方便理解之后的详解。

2. Pattern Filter Expression
Pattern的Filter表达式和普通的表达式没有区别，我就不展开讲解了，各位看看下面几个例子就好，除了Filter之外的东西暂时不用关心是什么意思。

1). every e1=RfidEvent -> e2=RfidEvent(assetId=e1.assetId)
2). every e1=RfidEvent -> e2=RfidEvent(MyLib.isInRadius(e1.x, e1.y, x, y) and zone in (1, e1.zone))
3). every (RfidEvent(zone > 1) and RfidEvent(zone < 10))

3. Controlling Event Consumption
       上面说到了Filter，因为Pattern可以由多个原子事件组成，那么Filter自然也会有多个，正常情况下，所有的Filter都会对进入引擎的事件进行判定，但是我们也有只需要判定一次的时候，只要满足了某个Filter，那么其他的Filter就不用管这个事件了。Esper考虑到了这个需求，我们只需要在Filter表达式后面加个@consume注解即可，此注解可以跟随数字，表示过滤的优先级。默认优先级为1，数值越大优先级越高。

为了结合上面几节的知识，我给了个完整的实例：

package example;

import com.espertech.esper.client.EPAdministrator;
import com.espertech.esper.client.EPRuntime;
import com.espertech.esper.client.EPServiceProvider;
import com.espertech.esper.client.EPServiceProviderManager;
import com.espertech.esper.client.EPStatement;
import com.espertech.esper.client.EventBean;
import com.espertech.esper.client.UpdateListener;

/**
 * Created by Luonanqin on 8/11/14.
 */
class ConsumeEvent {

	private int id;
	private String name;
	private int age;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String toString() {
		return "ConsumeEvent{" + "id=" + id + ", name='" + name + '\'' + ", age=" + age + '}';
	}
}

class PatternConsumeListener1 implements UpdateListener {

	public void update(EventBean[] newEvents, EventBean[] oldEvents) {
		if (newEvents != null) {
			for (int i = 0; i < newEvents.length; i++) {
				System.out.println("a: " + newEvents[i].get("a"));
				System.out.println("b: " + newEvents[i].get("b"));
			}
		}
	}
}

class PatternConsumeListener2 implements UpdateListener {

	public void update(EventBean[] newEvents, EventBean[] oldEvents) {
		if (newEvents != null) {
			for (int i = 0; i < newEvents.length; i++) {
				System.out.println("a: " + newEvents[i].get("a"));
				System.out.println("b: " + newEvents[i].get("b"));
				System.out.println("c: " + newEvents[i].get("c"));
			}
		}
	}
}

public class PatternConsumeTest {

	public static void main(String[] args) {
		EPServiceProvider epService = EPServiceProviderManager.getDefaultProvider();
		EPAdministrator admin = epService.getEPAdministrator();
		EPRuntime runtime = epService.getEPRuntime();

		String consume = ConsumeEvent.class.getName();

		String epl1 = "every (a=" + consume + "(id = 1)@consume and b=" + consume + "(name = 'luonq'))";
		System.out.println("EPL1: " + epl1 + "\n");

		EPStatement stat1 = admin.createPattern(epl1);
		stat1.addListener(new PatternConsumeListener1());

		ConsumeEvent ce1 = new ConsumeEvent();
		ce1.setId(1);
		ce1.setName("luonq");
		System.out.println("Send Event: " + ce1);
		runtime.sendEvent(ce1);

		System.out.println();

		ConsumeEvent ce2 = new ConsumeEvent();
		ce2.setId(2);
		ce2.setName("luonq");
		System.out.println("Send Event: " + ce2);
		runtime.sendEvent(ce2);

		stat1.destroy();
		System.out.println();

		String epl2 = "every (a=" + consume + "(id = 1)@consume(2) or b=" + consume + "(name = 'luonq')@consume(3) or c=" + consume + "(age > 2))";
		System.out.println("EPL2: " + epl2 + "\n");

		EPStatement stat2 = admin.createPattern(epl2);
		stat2.addListener(new PatternConsumeListener2());

		ConsumeEvent ce3 = new ConsumeEvent();
		ce3.setId(1);
		ce3.setName("luonq");
		ce3.setAge(3);
		System.out.println("Send Event: " + ce3);
		runtime.sendEvent(ce3);

		ConsumeEvent ce4 = new ConsumeEvent();
		ce4.setId(1);
		ce4.setName("luonqin");
		ce4.setAge(1);
		System.out.println("Send Event: " + ce4);
		runtime.sendEvent(ce4);

		ConsumeEvent ce5 = new ConsumeEvent();
		ce5.setId(3);
		ce5.setName("luonqin");
		ce5.setAge(5);
		System.out.println("Send Event: " + ce5);
		runtime.sendEvent(ce5);
	}
}

EPL1: every (a=example.ConsumeEvent(id = 1)@consume and b=example.ConsumeEvent(name = 'luonq'))

Send Event: ConsumeEvent{id=1, name='luonq', age=0}

Send Event: ConsumeEvent{id=2, name='luonq', age=0}
a: ConsumeEvent{id=1, name='luonq', age=0}
b: ConsumeEvent{id=2, name='luonq', age=0}

EPL2: every (a=example.ConsumeEvent(id = 1)@consume(2) or b=example.ConsumeEvent(name = 'luonq')@consume(3) or c=example.ConsumeEvent(age > 2))

Send Event: ConsumeEvent{id=1, name='luonq', age=3}
a: null
b: ConsumeEvent{id=1, name='luonq', age=3}
c: null
Send Event: ConsumeEvent{id=1, name='luonqin', age=1}
a: ConsumeEvent{id=1, name='luonqin', age=1}
b: null
c: null
Send Event: ConsumeEvent{id=3, name='luonqin', age=5}
a: null
b: null
c: ConsumeEvent{id=3, name='luonqin', age=5}

EPL1: every (a=example.ConsumeEvent(id = 1) and b=example.ConsumeEvent(name = 'luonq'))

Send Event: ConsumeEvent{id=1, name='luonq', age=0}
a: ConsumeEvent{id=1, name='luonq', age=0}
b: ConsumeEvent{id=1, name='luonq', age=0}

Send Event: ConsumeEvent{id=2, name='luonq', age=0}

EPL2: every (a=example.ConsumeEvent(id = 1) or b=example.ConsumeEvent(name = 'luonq') or c=example.ConsumeEvent(age > 2))

Send Event: ConsumeEvent{id=1, name='luonq', age=3}
a: ConsumeEvent{id=1, name='luonq', age=3}
b: null
c: null
Send Event: ConsumeEvent{id=1, name='luonqin', age=1}
a: ConsumeEvent{id=1, name='luonqin', age=1}
b: null
c: null
Send Event: ConsumeEvent{id=3, name='luonqin', age=5}
a: null
b: null
c: ConsumeEvent{id=3, name='luonqin', age=5}

本篇内容较少，主要是将一些必备的基础知识跟各位说说，下一篇会对围绕操作符展开，如果篇幅过长，可能会分成两篇为大家献上。敬请期待……

Esper学习之十四：Pattern（一）

标签：cep   esper   数据   开源   

原文地址：http://blog.csdn.net/luonanqin/article/details/38872729