# Variable Resolver

### Functionality

You can define variable resolvers to help you resolve expressions in the following format:

```highlight
#{name:key:element}
```

* `name`: The name of the metadata element to use to resolve the variable
* `key`: The key or path to use to retrieve the value.
* `element`: In case the value retrieved is in JSON form, we can pick one of the values out of it (OPTIONAL)

{% hint style="warning" %}
An error in resolving a variable does not lead to a failure on the level of a pipeline or workflow.
{% endhint %}

{% hint style="info" %}
Because of usability reasons, errors are not immediately shown in the user interface. It would become impossible to type in any expression because of it. Check the log in the [Hop GUI](/data-shaper-1.21/index-1/hop-gui.md) execution pane to see any errors thrown back by the resolvers.
{% endhint %}

{% hint style="info" %}
If you find that typing in variable expressions in a table view (table grid) is too slow, uncheck the option to resolve variables in tooltips in the [configuration perspective](/data-shaper-1.21/knowing-the-data-shaper-designer/index/perspectives/perspective-configuration.md).
{% endhint %}

### Nested resolving

Suppose you have a variable with its value being a resolve expression. In that case you’ll notice that when you ask for the value of the variable, the variable resolver also is being used.

For example, you can have a `PASSWORD` variable pointing to value `p@55w0rd` in a development environment, and to a secrets vault in production by setting `PASSWORD` to a resolver expression like:

```highlight
#{vault:secret/data/database:password}
```

When executing a pipeline or workflow, the value of variable `PASSWORD` will then first be resolved to the expression and then, using the variable resolver called `vault`, the password is retrieved from the secrets vault.

{% hint style="warning" %}
For now, the variable resolver is not doing any more nested resolving to avoid complications like infinite loops.
{% endhint %}

### Plugins

Here are the available variable resolver plugins:

* [Pipeline variable resolver](/data-shaper-1.21/knowing-the-data-shaper-designer/index-2/index/pipeline-variable-resolver.md)
* [Hashicorp Vault variable resolver](/data-shaper-1.21/knowing-the-data-shaper-designer/index-2/index/vault-variable-resolver.md)
* [Google Secret Manager Variable Resolver](/data-shaper-1.21/knowing-the-data-shaper-designer/index-2/index/google-secret-manager-variable-resolver.md)


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