在Jmeter中，我试图从json中提取值。这是我收到的json 响应：

    {
    Definition: {
        key: 1124,
        Id: 1743,
        srcID: "3427",
        pcKey: -1,
        userName: "abraizada",
        cName: "JMeter2016-11-27-1480283993838",
        Type: "SUBJECT",
        cohortTool: "Web app",
        cCount: 74,
        extractionStatus: "Completed",
        dateCreated: "2017-05-09T18:35:35Z"
    },
    datasource: {
        id: 2,
        name: "Claims-OMOP",
        subjectCount: 116352
    },
    project: {
        id: 747,
        name: "Jmeter Project"
    }
},
{
    cohortDefinition: {
        key: 1123,
        Id: 1742,
        srcID: "3447",
        pcKey: -1,
        userName: "IE_USER",
        cName: "JMeter2016-11-15-1479204865900",
        Type: "SUBJECT",
        cohortTool: "Web app",
        cCount: 74,
        extractionStatus: "",
        dateCreated: "2017-05-09T18:35:35Z"
    },
    datasource: {
        id: 2,
        name: "External",
        sCount: 116352
    },
    project: {
        id: 747,
        name: "Jmeter Project"
    }
},

从上面的响应中，如果srcID = 3447，我想提取值’key’。我试图做这个$ .. cohortKey [？（@。srcCohortId = 3447）]。cohortKey

但没有得到结果。谁能帮助我根据
条件提取“关键”价值。