# HTML Mask (HtmlMaskGenerator)

The [HTML Mask](https://docs.tonic.ai/app/generation/generators/generator-reference/html-mask) generator masks text columns. It parses the content as HTML, and applies sub-generators to specified path expressions.

If a sub-generator application fails because of an error, then Structural applies the fallback generator instead.

## Link object structure <a href="#generator-api-html-mask-link-object" id="generator-api-html-mask-link-object"></a>

For the HTML Mask generator, there is a link object for each XPath expression value to assign a generator to.

The generator does not itself support consistency or differential privacy.

The `metadata` object is populated from the [`HtmlMaskMetadata`](https://app.tonic.ai/apidocs/index.html#/models/HtmlMaskMetadata) object. It includes:

* `pathExpression`, which is the XPath expression that identifies the value to apply the sub-generator to.
* The `subGeneratorMetadata` object, which identifies and configures the sub-generator.

{% code overflow="wrap" %}

```json
{
  "schema": "string",
  "table": "string",
  "column": "string",
  "metadata": {
    "generatorId": "HtmlMaskGenerator",
    "customValueProcessor": "string",  //If custom value processor applied
    "pathExpression": "string",
    "subGeneratorMetadata": {
      "presetId": "string",
      "generatorId": "string",
      //Metadata for the selected sub-generator
      "customValueProcessor": "string"  //If custom value processor applied to the sub-generator
    }
  }
}
```

{% endcode %}

## Example replacement <a href="#generator-api-html-mask-replacement" id="generator-api-html-mask-replacement"></a>

In the following example replacement for the HTML Mask generator:

* The Character Scramble generator is assigned to the value of the XPath expression `//p`. Consistency is disabled.
* The Company Name generator is assigned to the value of the XPath expression `//p/@data`. Consistency is disabled.
* In the case of an error applying either of those generators, the fallback generator is the Constant generator, which sets the value to `10`.

```json
{
  "name": "html_data",
  "schema": "public",
  "table": "html_me",
  "links": [
    {
      "schema": "public",
      "table": "html_me",
      "column": "html_data",
      "metadata": {
        "generatorId": "HtmlMaskGenerator",
        "presetId": "HtmlMaskGenerator",
        "pathExpression": "//p",
        "subGeneratorMetadata": {
          "presetId": "TextMaskGenerator",
          "generatorId": "TextMaskGenerator",
          "isConsistent": false
        }
      }
    },
    {,
      "schema": "public",
      "table": "html_me",
      "column": "html_data",
      "metadata": {
        "generatorId": "HtmlMaskGenerator",
        "presetId": "HtmlMaskGenerator",
        "pathExpression": "//p/@data",
        "subGeneratorMetadata": {
          "presetId": "CompanyNameGenerator",
          "generatorId": "CompanyNameGenerator",
          "isConsistent": false
        }
      }
    }
  ],
  "fallbackLinks": [
    {
      "schema": "public",
      "table": "html_me",
      "column": "html_data",
      "metadata": {
        "presetId": "string",
        "generatorId": "ConstantGenerator",
        "constant": "10"
      }
    }
  ]
}
```


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