FIWARE CEP (Proton) 派生事件属性与聚合 EPA 错误

Question

我从 Orion 收到一个 ContextUpdate 事件，我设置了一个规则来计算在特定时间 window 内接收到的事件的数量，可能具有相同的 "entityId"。在聚合 EPA 的派生事件中，我希望 "DeviceID" 属性采用与接收到的事件的 "entityId" 相同的值。但是，无论是 "Defered" 还是 "Immediate" 评估策略，在消费者输出（文本文件）的 DeviceID 属性中，我都有：

"DeviceID":"[Ljava.lang.Object;@4456c43f"

有什么提示吗？

谢谢。

这里是 json 配置：

{
"epn": {
    "events": [{
        "name": "DCUPiazzaCarraraContextUpdate",
        "createdDate": "Thu Oct 22 2015",
        "attributes": [{
            "name": "entityId",
            "type": "String",
            "dimension": 0
        }, {
            "name": "entityType",
            "type": "String",
            "dimension": 0
        }, {
            "name": "battery",
            "type": "Double",
            "dimension": 0
        }, {
            "name": "temperature",
            "type": "Double",
            "dimension": 0
        }, {
            "name": "stato",
            "type": "Boolean",
            "dimension": 0
        }, {
            "name": "rssi",
            "type": "Integer",
            "dimension": 0
        }, {
            "name": "lqi",
            "type": "Integer",
            "dimension": 0
        }, {
            "name": "timestamp",
            "type": "String",
            "dimension": 0
        }, {
            "name": "numprog",
            "type": "Integer",
            "dimension": 0
        }, {
            "name": "dcu",
            "type": "String",
            "dimension": 0
        }]
    }, {
        "name": "DCUAbsence",
        "createdDate": "Sat Nov 07 2015",
        "attributes": [{
            "name": "entityId",
            "type": "String",
            "dimension": 0
        }, {
            "name": "entityType",
            "type": "String",
            "dimension": 0
        }, {
            "name": "AlertType",
            "type": "String",
            "dimension": 0
        }, {
            "name": "eventnum",
            "type": "Integer",
            "dimension": 0
        }, {
            "name": "DeviceID",
            "type": "String",
            "dimension": 0
        }, {
            "name": "DeviceContext",
            "type": "String",
            "dimension": 0
        }]
    }],
    "epas": [{
        "name": "AbsenceDCU",
        "createdDate": "Sat Nov 07 2015",
        "epaType": "Aggregate",
        "context": "AbsenceDCUComp",
        "inputEvents": [{
            "name": "DCUPiazzaCarraraContextUpdate",
            "consumptionPolicy": "Reuse",
            "instanceSelectionPolicy": "First"
        }],
        "computedVariables": [{
            "name": "eventnum",
            "aggregationType": "Count",
            "DCUPiazzaCarraraContextUpdate": "1"
        }],
        "evaluationPolicy": "Immediate",
        "cardinalityPolicy": "Unrestricted",
        "internalSegmentation": [],
        "derivedEvents": [{
            "name": "DCUAbsence",
            "reportParticipants": false,
            "expressions": {
                "entityId": "\"Alert\"",
                "entityType": "\"PiazzaCarrara\"",
                "AlertType": "\"006\"",
                "eventnum": "eventnum",
                "DeviceID": "DCUPiazzaCarraraContextUpdate.entityId",
                "DeviceContext": "DCUPiazzaCarraraContextUpdate.entityType"
            }
        }]
    }],
    "contexts": {
        "temporal": [{
            "name": "AbsenceDCUWindow",
            "createdDate": "Sat Nov 07 2015",
            "type": "TemporalInterval",
            "atStartup": false,
            "neverEnding": false,
            "initiators": [{
                "initiatorType": "Event",
                "initiatorPolicy": "Ignore",
                "name": "DCUPiazzaCarraraContextUpdate"
            }],
            "terminators": [{
                "terminatorType": "RelativeTime",
                "terminationType": "Discard",
                "relativeTime": "5000"
            }]
        }],
        "segmentation": [{
            "name": "AbsenceDCUID",
            "createdDate": "Thu Dec 17 2015",
            "participantEvents": [{
                "name": "DCUPiazzaCarraraContextUpdate",
                "expression": "DCUPiazzaCarraraContextUpdate.entityId"
            }, {
                "name": "DCUAbsence",
                "expression": "DCUAbsence.DeviceID"
            }]
        }],
        "composite": [{
            "name": "AbsenceDCUComp",
            "createdDate": "Thu Dec 17 2015",
            "temporalContexts": [{
                "name": "AbsenceDCUWindow"
            }],
            "segmentationContexts": [{
                "name": "AbsenceDCUID"
            }]
        }]
    },
    "consumers": [{
        "name": "OnFileAlert",
        "createdDate": "Thu Oct 22 2015",
        "type": "File",
        "properties": [{
            "name": "filename",
            "value": "/var/log/tomcat7/Alert.json"
        }, {
            "name": "formatter",
            "value": "json"
        }, {
            "name": "delimiter",
            "value": ";"
        }, {
            "name": "tagDataSeparator",
            "value": "="
        }, {
            "name": "SendingDelay",
            "value": "1000"
        }, {
            "name": "dateFormat",
            "value": "dd/MM/yyyy-HH:mm:ss"
        }],
        "events": [{
            "name": "DCUAbsence"
        }, {
            "name": "DCUPiazzaCarraraContextUpdate"
        }]
    }],
    "producers": [],
    "name": "CounterExample"
}

}

Answer 1

在类型为 Aggregate 的 EPA 中，由于来自该类型的许多事件可能会在上下文中到达，因此当您在派生表达式中引用输入事件属性时，您会得到一个array 保存该类型的所有参与者输入事件的属性。

在您的示例中，DCUPiazzaCarraraContextUpdate.entityId 将包含 array entityId。

如果您想要单个值，您可以使用数组访问函数从数组中获取一个值，或者由于您对 entityId 使用分段上下文，您可以从该上下文中获取 entityId。

要从上下文中获取属性，请使用 context."segmentation-context-name" 表达式，在您的情况下是：

context.AbsenceDCUID

在一般情况下，您可以使用数组访问函数从数组中获取特定条目。例如，从数组中获取最后一个值：

ArrayGet(DCUPiazzaCarraraContextUpdate.entityId, ArraySize(DCUPiazzaCarraraContextUpdate.entityId)-1)

FIWARE CEP (Proton) 派生事件属性与聚合 EPA 错误

FIWARE CEP (Proton) Error in derived event attributes with Aggregate EPA

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