Esper事件处理引擎_8_EPL 语法_2_Context 上下文_2_条件控制

EPL_2_Context_2

package com.framework_technology.esper.epl_context;

import com.framework_technology.esper.javabean.Apple;

/**
* Created by IntelliJ IDEA.
* User: wei.Li
* Date: 14-8-7
* <p>
* 1.类别分组新建 context        {@link #contextCategorySegmented()}
* 2.通过开始和结束条件控制 context 的新建和停止（重叠和非重叠）     {@link #contextNon_Overlapping(),#contextOverlapping()}
* 3.不同的事件的起始条件        {@link #contextDistinctEventsForTheInitiatingCondition()}
*/
public class EPL_2_Context_2 {

/**
* 类别分组 context
* <p>
* create context context_name
* group [by] group_expression as category_label
* [, group [by] group_expression as category_label]
* [, ...]
* from stream_def
* <p>
* group_expression表示分组策略的表达式，category_label为策略定义一个名字，一个context可以有多个策略同时存在，但是特殊的是之能有一个stream_def。
* <p>
* Name	    Description
* ===================================================
* name	    The string-type context name.
* id	    The integer-type internal context id that the engine assigns to the context partition.
* label	类别标签的字符串标识符值后所指定的每一组的作为关键字。
*
* @return epl[]
*/
protected static String[] contextCategorySegmented() {
String epl1 = "create context esbtest group by price<0 as low, group by price>0 and price<10 as middle,group by price>10 as high from " + Apple.CLASSNAME;
String epl2 = "context esbtest select context.id,context.name,context.label, price from " + Apple.CLASSNAME;

return new String[]{epl1, epl2};
}

/**
* 一次或重复的规则的方式通过开始和结束条件控制。
* 上下文的分区数始终为1或零：上下文分区不重叠。
* <p>
* create context context_name
* start (@now | start_condition)
* end end_condition
*
* @return epl[]
*/
protected static String[] contextNon_Overlapping() {
//上午9点-下午5点间启动 context，过滤价格大于100的事件
String epl1 = "create context NineToFive start (0, 9, *, *, *) end (0, 17, *, *, *)";
String epl2 = "context NineToFive select * from " + Apple.CLASSNAME + "(price >= 100)";

//下面的语句在停电期间，并持续5秒输出温度的动力：
String epl3 = "create context PowerOutage start PowerOutageEvent end pattern [PowerOnEvent -> timer:interval(5)]";
String epl4 = "context PowerOutage select * from TemperatureEvent";

//语句创建立即开始，持续15分钟，以15分钟的间隔一再分配一个新的上下文分区context Every15Minutes ：
String epl5 = "create context Every15Minutes start @now end after 15 minutes";

return new String[]{epl1, epl2};
}

/**
* OverLapping和NoOverLapping一样都有两个条件限制，{@link EPL_2_Context_2#contextNon_Overlapping()}
* 但是区别在于OverLapping的初始条件可以被触发多次，并且只要被触发就会新建一个context，但是当终结条件被触发时，之前建立的所有context都会被销毁。
* <p>
* create context context_name
* initiated [by] [distinct (distinct_value_expr [,...])] [@now and] initiating_condition
* terminated [by] terminating_condition
*
* @return epl[]
*/
protected static String[] contextOverlapping() {
// Apple进入 事件触发开始，5分钟后结束
String epl1 = "create context CtxTrainEnter initiated by " + Apple.CLASSNAME + " as te  terminated after 5 minutes";
String epl4 = "context CtxTrainEnter select context.name, context.startTime, context.endTime , a.* from " + Apple.CLASSNAME + "(price >= 10) as a";

//TODO unsolved
String epl2 = "context CtxTrainEnter" +
"select t1 from pattern [" +
"  t1=TrainEnterEvent -> timer:interval(5 min) and not TrainLeaveEvent(trainId = context.te.trainId)" +
"  ]";
//TODO unsolved 每隔一分钟新建一个，一分钟后停止
String epl3 = "create context CtxEachMinute initiated @now and pattern [every timer:interval(1 minute)] terminated after 1 minutes";

return new String[]{epl1, epl4};
}

/**
* 不同的事件的起始条件
* <p>
* 请注意以下限制：
* <p>
* 1.distinct关键字需要事件流的初始条件(例如,而不是crontab或模式)和流名称必须分配使用关键字。
* 2.子查询、聚合和特殊上一页和前函数是不允许在distinct-value表达式。
*
* @return EPL
*/
protected static String[] contextDistinctEventsForTheInitiatingCondition() {
// NewOrderEvent的不同的orderId进入 事件触发开始，CloseOrderEvent进入后根据orderId是否相等停止
String epl1 = "create context OrderContext" +
"  initiated by distinct(orderId) NewOrderEvent as newOrder " +
"  terminated by CloseOrderEvent(closeOrderId = newOrder.orderId)";

return new String[]{epl1};
}

/**
*  上下文startTime/endTime

Name	    Description
=================================================
name	    The string-type context name.
startTime	分区的开始时间上下文。
endTime	分区的结束时间上下文。分区的结束时间上下文。这个字段是唯一可用的情况下,它可以计算从crontab或提供时间表达式。

*/

}