demo 解读

有了第一篇的基础,操作jolt已经不成问题,对于大部分json的mapping已经得心应手了,本片主要聚焦jolt除了json的mapping功能以外的其他功能。

数据相关 - List Functions

json input

{
  "scores": [
    4,
    2,
    8,
    7,
    5
  ]
}

json spec

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      // 计算数组长度
      "numScores": "=size(@(1,scores))",
      // 数组取头取尾
      "firstScore": "=firstElement(@(1,scores))",
      "lastScore": "=lastElement(@(1,scores))",
      // 出不来值
      "scoreAtMidPoint": "=elementAt(@(1,scores),2)",
      // 数组排序
      "sortedScores": "=sort(@(1,scores))"    }
  }
]

json output

{
  "scores" : [ 4, 2, 8, 7, 5 ],
  "numScores" : 5,
  "firstScore" : 4,
  "lastScore" : 5,
  "sortedScores" : [ 2, 4, 5, 7, 8 ]
}

数学相关 - Math Functions

json input

{
  "intData" : [ 2, 7, 5 ],
  "doubleData" : [ 0.25, 1.5, 1 ],

  "a" : 10,
  "b" : 5,
  "c" : 3,

  "negative" : "-1.0"
}

json spec

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      //
      // Sums
      "sumIntData": "=intSum(@(1,intData))",
      "sumLongData": "=intSum(@(1,intData))", // same as intSum but returns a Java Long
      "sumDoubleData": "=doubleSum(@(1,doubleData))",
      //
      // Averages
      "avgIntData" : "=avg(@(1,intData))",    // note this returns a double
      "avgDoubleData" : "=avg(@(1,doubleData))",
      //
      // Sort ascending
      "sortedIntScores" : "=sort(@(1,intData))",
      //
      // Min, Max, Absolute Value
      "minAB" : "=min(@(1,a),@(1,b))",  // should be 5
      "maxAB" : "=max(@(1,a),@(1,b))",  // should be 10
      "abs" : "=abs(@(1,negative))",
      //
      // Divide
      "aDivB": "=divide(@(1,a),@(1,b))",
      "aDivC": "=divide(@(1,a),@(1,c))", // will be 3.3333
      //
      // Divide and Round : decimal point to round to is first param
      "aDivCRounded4": "=divideAndRound(4,@(1,a),@(1,c))"
    }
  }
]

json output

{
  "intData" : [ 2, 7, 5 ],
  "doubleData" : [ 0.25, 1.5, 1 ],
  "a" : 10,
  "b" : 5,
  "c" : 3,
  "negative" : "-1.0",
  "sumIntData" : 14,
  "sumLongData" : 14,
  "sumDoubleData" : 2.75,
  "avgIntData" : 4.666666666666667,
  "avgDoubleData" : 0.9166666666666666,
  "sortedIntScores" : [ 2, 5, 7 ],
  "minAB" : 5,
  "maxAB" : 10,
  "abs" : 1.0,
  "aDivB" : 2.0,
  "aDivC" : 3.3333333333333335,
  "aDivCRounded4" : 3.3333
}

类型转换 - Type Conversion

json input

{
  "happy": "true",
  "meh": "meh",
  "answer": 42,

  "statistics" : [
    {
      "id" : "A",
      "min" : "2.0",
      "max" : "10.0",
      "avg" : "7.9"
    },
    {
      "min" : "6",
      "max" : "6",
      "avg" : "6"
    },
    {
      "id" : "C"
    }
  ]
}
    

json spec

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      // convert strings to a boolean, case-insensitive
      "happy": "=toBoolean",
      // meh might not be a boolean, so if it does not evaluate to a boolean
      //  then default in a boolean of false
      "meh": ["=toBoolean", false],
      //
      // convert the number to a String
      "answer": "=toString",
      //
      //
      // Here we want to do some type conversions, and specify
      //  default values for missing data.
      "statistics": {
        "*": {
          // Overwrite min, max, and avg by type converting them.
          // If they don't exist, then fill in default values.
          "min": ["=toInteger", 0],
          "max": ["=toInteger", null],
          "avg": ["=toDouble", null],
          //
          // In this example, min, max, and average "overwrite"
          // is the right thing to do (why the operation is
          //   "modify-overwrite-beta")
          //
          // Note that the 2nd item in the list does not have and "id"
          //  field.
          //
          // Is this instane, we don't actually want to "overwrite" the "id" it exists
          //  but we do want to apply a default if it does not.
          // In the input, the 2nd item in the "statistics" array is missing its id.
          //
          // The solution is to apply a "node level" change of behavior from
          //  "overwrite" to "define", so that we will only fill in the id if it is missing.
          //
          // To do this we prefix the ke, "id", with an underscore, "_".
          "_id": "UNKNOWN"
        }
      }
    }
  }
]

json output

{
  "happy" : true,
  "meh" : false,
  "answer" : "42",
  "statistics" : [ {
    "id" : "A",
    "min" : 2,
    "max" : 10,
    "avg" : 7.9
  }, {
    "min" : 6,
    "max" : 6,
    "avg" : 6.0,
    "id" : "UNKNOWN"
  }, {
    "id" : "C",
    "min" : 0,
    "max" : null,
    "avg" : null
  } ]
}

字符串连接 - String Concatenation

json input

{
  "x": [ 3, 2, 1, "go"  ],
  "small": "small",
  "BIG": "BIG",

  "people": [
    {
      "firstName": "Bob",
      "lastName": "Smith",
      "address": {
        "state": null
      }
    },
    {
      "firstName": "Sterling",
      "lastName": "Archer"
    }
  ]
}

json spec

[
  {
    "operation": "modify-default-beta",
    "spec": {
      // String join the values in the array x, with a comma and a space
      "y": "=join(',',@(1,x))",
      "z": "=join(' ',@(1,x))",
      //
      // make small big, and make big small
      "small_toUpper": "=toUpper(@(1,small))",
      "BIG_toLower": "=toLower(@(1,BIG))",
      //
      // Here we are dealing with an array of people objects.
      // We want to build a fullName for them, and default them
      // to 'live' in Texas, only if they don't already have an address defined.
      "people": {
        "*": {
          // build the fullName from the first and last names
          //
          // @(1,firstName)
          //  -  is "evaluated" before being passed to the =concat function.
          //  -  means go up two levels, and then come back down and grab
          //      the value from firstName
          "fullName": "=concat(@(1,firstName),' ',@(1,lastName))",
          //
          // Suffix of "?" means only match if the input actually has an "address"
          "address?": {
            // The transform "modify-default-beta" will only match if the
            //  "left hand side" does not exist or is null
            "state": "Texas"
          }
        }
      }
    }
  }
]

json output

{
  "x" : [ 3, 2, 1, "go" ],
  "small" : "small",
  "BIG" : "BIG",
  "people" : [ {
    "firstName" : "Bob",
    "lastName" : "Smith",
    "address" : {
      "state" : "Texas"
    },
    "fullName" : "Bob Smith"
  }, {
    "firstName" : "Sterling",
    "lastName" : "Archer",
    "fullName" : "Sterling Archer"
  } ],
  "y" : "3,2,1,go",
  "z" : "3 2 1 go",
  "small_toUpper" : "SMALL",
  "BIG_toLower" : "big"
}