druid json格式数据源，多层嵌套官方样例测试，发现两处语法错误bug

官方提供了下面的样例进行嵌套json扁平化：

{
 "timestamp": "2015-09-12T12:10:53.155Z",
 "dim1": "qwerty",
 "dim2": "asdf",
 "dim3": "zxcv",
 "ignore_me": "ignore this",
 "metrica": 9999,
 "foo": {"bar": "abc"},
 "foo.bar": "def",
 "nestmet": {"val": 42},
 "hello": [1.0, 2.0, 3.0, 4.0, 5.0],
 "mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],
 "world": [{"hey": "there"}, {"tree": "apple"}],
 "thing": {"food": ["sandwich", "pizza"]}
}

我对这个样例进行了批量，并传输至kakfa中,截取一小段：

{"timestamp": "2018-12-20T14:12:39","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}
{"timestamp": "2018-12-20T14:12:39","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}
{"timestamp": "2018-12-20T14:12:40","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}
{"timestamp": "2018-12-20T14:12:40","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}
{"timestamp": "2018-12-20T14:12:40","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}
{"timestamp": "2018-12-20T14:12:41","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}
{"timestamp": "2018-12-20T14:12:41","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}
{"timestamp": "2018-12-20T14:12:41","dim1": "qwerty","dim2": "asdf","dim3": "zxcv","ignore_me": "ignore this","metrica": 9999,"foo": {"bar": "abc"},"foo.bar": "def","nestmet":{"val": 42},"hello": [1.0, 2.0, 3.0, 4.0, 5.0],"mixarray": [1.0, 2.0, 3.0, 4.0, {"last": 5}],"world": [{"hey": "there"}, {"tree": "apple"}],"thing": {"food": ["sandwich", "pizza"]}}

官方给的解析方式：

"parseSpec": {
  "format": "json",
  "flattenSpec": {
    "useFieldDiscovery": true,
    "fields": [
      {
        "type": "root",
        "name": "dim1"
      },
      "dim2",
      {
        "type": "path",
        "name": "foo.bar",
        "expr": "$.foo.bar"
      },
      {
        "type": "root",
        "name": "foo.bar"
      },
      {
        "type": "path",
        "name": "path-metric",
        "expr": "$.nestmet.val"
      },
      {
        "type": "path",
        "name": "hello-0",
        "expr": "$.hello[0]"
      },
      {
        "type": "path",
        "name": "hello-4",
        "expr": "$.hello[4]"
      },
      {
        "type": "path",
        "name": "world-hey",
        "expr": "$.world[0].hey"
      },
      {
        "type": "path",
        "name": "worldtree",
        "expr": "$.world[1].tree"
      },
      {
        "type": "path",
        "name": "first-food",
        "expr": "$.thing.food[0]"
      },
      {
        "type": "path",
        "name": "second-food",
        "expr": "$.thing.food[1]"
      },
      {
        "type": "jq",
        "name": "first-food-by-jq",
        "expr": ".thing.food[1]"
      },
      {
        "type": "jq",
        "name": "hello-total",
        "expr": ".hello | sum"
      }
    ]
  },
  "dimensionsSpec" : {
   "dimensions" : [],
   "dimensionsExclusions": ["ignore_me"]
  },
  "timestampSpec" : {
   "format" : "auto",
   "column" : "timestamp"
  }
}

生成数据源后，发现不读取kafka数据，检查发现拉取数据的进程失败了，原因是有相同字段field出现：

      {
        "type": "path",
        "name": "foo.bar",
        "expr": "$.foo.bar"
      },
      {
        "type": "root",
        "name": "foo.bar"
      },

修改为这样重启：

      {
        "type": "path",
        "name": "foo-bar",
        "expr": "$.foo.bar"
      },
      {
        "type": "root",
        "name": "foo.bar"
      },

重启后日志仍然报错，原因是jq没有sum函数：

        "type": "jq",
        "name": "hello-total",
        "expr": ".hello | sum"
      }

去掉后重启恢复正常。

找到原因后，又测试了3层，4层嵌套，都能扁平化flatten，没找到不确定长度数组怎么添加field key。

jq的函数没找到怎么数组sum求和。

jackson-jq  github： https://github.com/eiiches/jackson-jq

jackson-jq  官网：https://stedolan.github.io/jq/

json-path github：https://github.com/json-path/JsonPath

官方路径：http://druid.io/docs/latest/ingestion/flatten-json.html