【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】。