我想从mt消息中找到一些mandatoy字段，并将其Map到基于pacs008格式的jsonapi格式。怎么做？下面给出了输出api响应的示例。我需要知道如何从mt消息中读取这些feild的值。如果有任何文件，请提供给我。

{
"grpHdr": {
"msgId": "12345",
"creDtTm": "2020-09-21T09:30:10Z",
"instgAgt": {
"finInstnId": {
"bicfi": "BICCDXXX",
"nm": "BANK X",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
},
"brnchId": {
"id": "Branch123",
"nm": "Branch Name",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
}
},
"instdAgt": {
"finInstnId": {
"bicfi": "BICCDXXX",
"nm": "BANK X",
"pstlAdr": {
"adrTp": {
"cd": "ADDR",
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
},
"brnchId": {
"id": "Branch123",
"nm": "Branch Name",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
}
}
},
"orgnlGrpInfAndSts": [{
"orgnlMsgId": "Original Message ID",
"orgnlMsgNmId": "Original message name identifier",
"orgnlCreDtTm": "2020-09-21T09:30:10Z",
"orgnlNbOfTxs": "1",
"orgnlCtrlSum": 100,
"grpSts": "RJCT",
"stsRsnInf": [{
"orgtr": {
"nm": "JOHN DOE",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
},
"id": {
"prvtId": {
"dtAndPlcOfBirth": {
"birthDt": "2020-09-21T09:30:10Z",
"prvcOfBirth": "NEW YORK",
"cityOfBirth": "NEW YORK",
"ctryOfBirth": "US"
},
"othr": [{
"id": "ABC123AB",
"schmeNm": {
"cd": "CCPT"
},
"issr": "United States"
}]
}
},
"ctryOfRes": "US"
},
"rsn": {
"cd": "AC04"
},
"addtlInf": ["The account is closed"]
}]
}],
"txInfAndSts": [{
"stsId": "DECLINED",
"orgnlTxId": "1234",
"txSts": "RJCT",
"instgAgt": {
"finInstnId": {
"bicfi": "BICCDXXX",
"nm": "BANK X",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
},
"brnchId": {
"id": "Branch123",
"nm": "Branch Name",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
}
},
"instdAgt": {
"finInstnId": {
"bicfi": "BICCDXXX",
"nm": "BANK X",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
},
"brnchId": {
"id": "Branch123",
"nm": "Branch Name",
"pstlAdr": {
"adrTp": {
"cd": "ADDR"
},
"strtNm": "Street Name",
"ctrySubDvsn": "New York",
"ctry": "US"
}
}
}
}]
}