如何编写通用Jolt转换规则实现嵌套数据转线性数据

先明确要覆盖的4种输入场景及对应输出效果：

场景1：subList元素包含S1、S2字段 #

输入：

{
  "practice_loc": "NY",
  "prac_num": "PN001",
  "topId": "T100",
  "subList": [
    {"S1": "s1_val1", "S2": "s2_val1"},
    {"S1": "s1_val2", "S2": "s2_val2"}
  ]
}

输出：

[
  {
    "practice_loc": "NY",
    "prac_num": "PN001",
    "topId": "T100",
    "S1": "s1_val1",
    "S2": "s2_val1"
  },
  {
    "practice_loc": "NY",
    "prac_num": "PN001",
    "topId": "T100",
    "S1": "s1_val2",
    "S2": "s2_val2"
  }
]

场景2：subList元素仅含S1字段 #

输入：

{
  "practice_loc": "CA",
  "prac_num": "PN002",
  "topId": "T200",
  "subList": [
    {"S1": "s1_val3"},
    {"S1": "s1_val4"}
  ]
}

输出：

[
  {
    "practice_loc": "CA",
    "prac_num": "PN002",
    "topId": "T200",
    "S1": "s1_val3"
  },
  {
    "practice_loc": "CA",
    "prac_num": "PN002",
    "topId": "T200",
    "S1": "s1_val4"
  }
]

场景3：subList元素仅含S2字段 #

输入：

{
  "practice_loc": "TX",
  "prac_num": "PN003",
  "topId": "T300",
  "subList": [
    {"S2": "s2_val5"},
    {"S2": "s2_val6"}
  ]
}

输出：

[
  {
    "practice_loc": "TX",
    "prac_num": "PN003",
    "topId": "T300",
    "S2": "s2_val5"
  },
  {
    "practice_loc": "TX",
    "prac_num": "PN003",
    "topId": "T300",
    "S2": "s2_val6"
  }
]

场景4：subList元素无S1、S2字段 #

输入：

{
  "practice_loc": "FL",
  "prac_num": "PN004",
  "topId": "T400",
  "subList": [
    {},
    {}
  ]
}

输出：

[
  {
    "practice_loc": "FL",
    "prac_num": "PN004",
    "topId": "T400"
  },
  {
    "practice_loc": "FL",
    "prac_num": "PN004",
    "topId": "T400"
  }
]

通用Jolt转换规则 #

[
  {
    "operation": "shift",
    "spec": {
      "subList": {
        "*": {
          "@(2,practice_loc)": "[&1].practice_loc",
          "@(2,prac_num)": "[&1].prac_num",
          "@(2,topId)": "[&1].topId",
          "S1": "[&1].S1",
          "S2": "[&1].S2"
        }
      }
    }
  }
]

规则说明 #

• shift是Jolt重组JSON结构的核心操作，负责字段映射与结构展平
• subList.*遍历数组内每个元素，&1代表当前元素的索引，用来定位输出数组的对应位置
• @(2,practice_loc)表示向上回溯2层（从subList元素层到根节点）提取字段值，复制到当前输出记录中
• S1、S2字段直接映射到输出位置，原元素无对应字段时，输出自动忽略，适配所有场景

内容的提问来源于stack exchange，提问作者dracile