功能：该语法是针对所查询事件中的属性又是另一种属性的查询结果控制。
格式：
| 1 | [select select_expressions from] |
| 2 | contained_expression [@type(eventtype_name)] [as alias_name] |
| 3 | [where filter_expression] |
说明:
该语法的重点在于contained_expression，这个表达式需要返回事件的属性，该属性可以是另一个事件也可以是普通数据类型，也可以是一组查询结果，比如一个数组，一个集合等等；
示例：
文件名:orderEvent.java
| 1 | public class orderEvent { |
| 2 | //基本数据类型 |
| 3 | private String name; |
| 4 | private int salary; |
| 5 | private orderArray orderAry; |
| 6 | |
| 7 | public orderArray getOrderAry() { |
| 8 | return orderAry; |
| 9 | } |
| 10 | public void setOrderAry(orderArray orderAry) { |
| 11 | this.orderAry = orderAry; |
| 12 | } |
| 13 | .......................... |
| 14 | } |
文件名：orderArray
| 1 | public class orderArray { |
| 2 | private List<orderBean> orderBeans; |
| 3 | |
| 4 | public List<orderBean> getOrderBeans() { |
| 5 | return orderBeans; |
| 6 | } |
| 7 | |
| 8 | public void setOrderBeans(List<orderBean> orderBeans) { |
| 9 | this.orderBeans = orderBeans; |
| 10 | } |
| 11 | |
| 12 | @Override |
| 13 | public String toString() { |
| 14 | return "orderArray [orderBeans=" + orderBeans + "]"; |
| 15 | } |
| 16 | } |
文件名: orderBean.java
| 1 | public class orderBean { |
| 2 | private String key; |
| 3 | private String value; |
| 4 | private orderItem bean; |
| 5 | |
| 6 | // 各个字段对应的get和set方法 |
| 7 | //............................. |
| 8 | |
| 9 | @Override |
| 10 | public String toString() { |
| 11 | return "orderBean [key=" + key + ", value=" + value + ", bean=" + bean |
| 12 | + "]"; |
| 13 | } |
| 14 | } |
文件名: orderItem.java
| 1 | public class orderItem { |
| 2 | private String name; |
| 3 | private String size; |
| 4 | |
| 5 | // 各属性字段对应的get和set方法 |
| 6 | //................................. |
| 7 | |
| 8 | @Override |
| 9 | public String toString() { |
| 10 | return "orderItem [name=" + name + ", size=" + size + "]"; |
| 11 | } |
| 12 | } |
文件名: orderMainTest(程序入口)
| 1 | int i = 8; |
| 2 | int seed = (int) (Math.random() * 100); |
| 3 | orderEvent event = new orderEvent("张", 100 + seed); |
| 4 | System.out.println("seed name:" + event.getName() + ",salary:" |
| 5 | + event.getSalary()); |
| 6 | orderBean bean = new orderBean(); |
| 7 | bean.setKey("BeanKey:" + i); |
| 8 | bean.setValue("BeanValue:" + i); |
| 9 | event.setBean(bean); |
| 10 | |
| 11 | List<orderBean> list = new ArrayList<orderBean>(); |
| 12 | for (int j = 0; j < 10; j++) { |
| 13 | bean = new orderBean(); |
| 14 | bean.setKey("ListKey:" + j); |
| 15 | bean.setValue("ListValue:" + j); |
| 16 | orderItem item = new orderItem(); |
| 17 | item.setName("chenx"); |
| 18 | item.setSize("100"+j); |
| 19 | bean.setBean(item); |
| 20 | list.add(bean); |
| 21 | } |
| 22 | |
| 23 | orderArray ary = new orderArray(); |
| 24 | ary.setOrderBeans(list); |
| 25 | event.setOrderAry(ary); |
| 26 | event.setOrderBeans(list); |
| 27 | |
| 28 | String epsql = "select * from orderEvent[orderAry.orderBeans][bean]"; |
| 29 | EPStatement epstate = epAdmin.createEPL(epsql); |
| 30 | epstate.addListener(new orderListener()); |
| 31 | |
| 32 | epRuntime.sendEvent(event); |
说明：
1、epl执行语句为 select * from orderEvent[orderAry.orderBeans] 表示查询orderEvent事件中orderAry事件属性字段中的orderBeans 事件，因为orderEvent与orderAry、orderAry与orderBeans都是有一种嵌套关系，就像类中有类一样是具有层次的；
2、epl执行语句为 select * from orderEvent[orderAry.orderBeans][bean] 表示只查询orderItem事件信息(bean为orderItem类型)， 因为orderAry.orderBeans返回的是orderBean类型的数组，而orderItem又是orderBean的属性成员（bean与orderAry.orderBeans不在一个层面上），所以[orderAry.orderBeans][bean]表示的返回orderItem事件;
3、返回结果的数据格式，由各事件类的toString函数定义；
4、Contained-Event在join查询中,如果事件来自于named window，那么连接操作就必须加上unidirectional关键字,作用为每次连接操作的结果都独立起来；
示例：
| 1 | String join5 = "select count(*) from " + mediaOrder + "[books.book] as book unidirectional, " + mediaOrder |
| 2 | + "[items.item] as item where productId = bookId"; |
| 3 | String join4 = "select count(*) from " + mediaOrder + "[books.book] as book, " + mediaOrder |
| 4 | + "[items.item] as item where productId = bookId"; |
说明：
Join4中当发送两个同样的mediaOrder对象，聚合函数count是要累加，而join5不会;