多层 JSON 转换成 CSV
【问题】
This is how my json looks like:
{
“data” :
[
{ “f1” : “v1”,
“f2” : “v2”,
“group” : [
{ “f3” : “x1”,
“f4” : “y1”,
“f5” : “z1”
},
{ “f3” : “x1”,
“f4” : “y2”,
“f5” : “z2”
},
{ “f3” : “x2”,
“f4” : “y3”,
“f5” : “z3”
}]
},
{ “f1” : “vf1”,
“f2” : “vf2”,
“group” : [
{ “f3” : “x1”,
“f4” : “y1”,
“f5” : “z1”
},
{ “f3” : “x1”,
“f4” : “y2”,
“f5” : “z2”
},
{ “f3” : “x1”,
“f4” : “y3”,
“f5” : “z3”
}]
}
]
}
I am using the following code to convert it into Csv:
JSONArray array = (JSONArray)json.get(“data”);
String dataCSV = CDL.toString(array);
But this code is giving me “null” in dataCSV.
I want to know why it is getting null in dataCSV and also please provide a solution on “How to get CSV from this JSON ?” or “from a POJO Class to CSV”.
Thanks in advance
【回答】
f1,f2 是上级（相当于分组字段），需要重复拼到下级（相当于组内明细），也就是将多层 json 转为单层（二维表），这样才能输出为 csv。用 SPL 实现这个过程比较简单：
| A | |
|---|---|
| 1 | =file(“d:\\data.json”).read() |
| 2 | =json(A1).dat |
| 3 | =A2.news(group;A2.f1,A2.f2,f3,f4,f5) |
| 4 | =file(“d:\\result.csv”).export@c(A3) |
A3 运行结果：
A1：读取 JSON
A2：解析 json 获得 data 节点
A3：提取所需字段生成新序列
A4 输出到 csv 文件
这段代码可以方便地集成进 Java，参考【Java 如何调用 SPL 脚本】。
