Struct TransformSpec 

pub struct TransformSpec(/* private fields */);

The JSON transformation specification.

Composes a list of operation specifications. Each operation has its own DSL (Domain Specific Language) in order to facilitate its narrow job.

use harmony_jolt::TransformSpec;

let spec: TransformSpec =
serde_json::from_str(r#"[
    {
      "operation": "shift",
      "spec": {
        "name": "data.name",
        "account": "data.account"
      }
    }
  ]"#).unwrap();

Shift operation

Specifies where the data from the input JSON should be placed in the output JSON, or in other words, how the input JSON/data should be shifted around to make the output JSON/data.

At a base level, a single shift operation is a mapping from an input path to an output path, similar to the mv command in Unix, mv /var/data /var/backup/data.

The input path is a JSON tree structure, and the output path is flattened “dot notation” path notation.

For example, given this simple input JSON:

{
    "id": 1,
    "name": "John Smith",
    "account": {
        "id": 1000,
        "type": "Checking"
    }
}

A simple spec could be constructed by copying that input, and modifying it to supply an output path for each piece of data:

{
    "id": "data.id",
    "name": "data.name",
    "account": "data.account"
}

would produce the following output JSON:

{
    "data" : {
        "id": 1,
        "name": "John Smith",
        "account": {
            "id": 1000,
            "type": "Checking"
        }
    }
}

Wildcards

The shift specification on the keys level supports wildcards and conditions:
1. * - match everything
2. name1|name2|nameN - match any of the specified names

& lookup allows referencing the values captured by the * or |.
It allows for specs to be more compact. For example, for this input:

{
    "id": 1,
    "name": "John Smith",
    "account": {
        "id": 1000,
        "type": "Checking"
    }
}

to get the output:

{
    "data" : {
        "id": 1,
        "name": "John Smith",
        "account": {
            "id": 1000,
            "type": "Checking"
        }
    }
}

the spec with wildcards would be:

{
    "*": "data.&0"
}

If you want only id and name in the output, the spec is:

{
    "id|name": "data.&0"
}

& wildcard also allows to dereference any level of the path of given node:

{
    "foo": {
        "bar" : {
            "baz": "new_location.&0.&1.&2" // &0 = baz, &1 = bar, &2 = foo
            }
        }
    }
}

for the input:

{
    "foo": {
      "bar": {
        "baz": "value"
      }
    }
  }

will produce:

{
    "new_location": {
      "baz": {
        "bar": {
          "foo": "value"
        }
      }
    }
}

Default operation

Applies default values if the value is not present in the input JSON.

For example, given this simple input JSON:

{
    "phones": {
        "mobile": 01234567,
        "country": "US"
    }
}

with the following specification for default operation:

{
    "phones": {
        "mobile": 0000000,
        "code": "+1"
    }
}

the output JSON will be:

{
    "phones": {
        "mobile": 01234567,
        "country": "US",
        "code": "+1"
    }
}

As you can see, the field mobile remains not affected while the code has a default ‘+1’ value.

Remove operation

Removes content from the input JSON. The spec structure matches the input JSON structure. The value of fields is ignored.

For example, given this simple input JSON:

{
    "phones": {
        "mobile": 01234567,
        "country": "US"
    }
}

you can remove the country by the following specification for remove operation:

{
    "phones": {
        "country": ""
    }
}

the output JSON will be:

{
    "phones": {
        "mobile": 01234567
    }
}

Trait Implementations

impl Clone for TransformSpec

fn clone(&self) -> TransformSpec

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TransformSpec

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for TransformSpec

fn default() -> TransformSpec

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for TransformSpec

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for TransformSpec

fn eq(&self, other: &TransformSpec) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for TransformSpec