> ## Documentation Index
> Fetch the complete documentation index at: https://doc.lucidworks.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Template Expressions
export const LwTemplate = ({title = "Key questions to get you started", icon = "sparkles", cta = "Powered by Agent Studio", linkHref = "https://lucidworks.com/demo/?utm_source=docs&utm_medium=referral&utm_campaign=docs_cta_ai"}) => {
const [isLoaded, setIsLoaded] = useState(false);
useEffect(() => {
const timer = setTimeout(() => {
setIsLoaded(true);
}, 500);
return () => clearTimeout(timer);
}, []);
return
{isLoaded && `
}} />}
Powered by Lucidworks Agent Studio
;
};
[localhost link]: http://localhost:3000/docs/5/fusion/getting-data-out/query-enhancement/template-expressions/overview
[mintlify link]: https://doc.lucidworks.com/docs/5/fusion/getting-data-out/query-enhancement/template-expressions/overview
[old doc.lw link]: https://doc.lucidworks.com/fusion/5.9/10911
Template expressions are a way to map field values in a document. They are used to configure some Fusion index pipeline stages, query pipeline stages, and messaging services. When the value of a configuration parameter is a template expression, that expression is dynamically evaluated at runtime by the [StringTemplate](https://github.com/antlr/stringtemplate4/blob/master/doc/cheatsheet.md) library.
Fusion template expressions are delimited by angle bracket characters `<` and `>`.
The expression consists of the name of a variable in the scope of that component.
Since these variables are Java objects, if object **foo** of type Foo has a field named **bar**, the expression **``** will evaluate to the string representation of the contents of field **bar**.
For example, given a PipelineDocument where a field named **title** has a value of **Star Wars**, the template expression `` evaluates to **Star Wars**.
## Index pipeline stage template expression variables
Index stages have the following variables available:
* `ctx`. [Context](https://javadoc.lucidworks.com/fusion-pipeline-javadocs/5.9/com/lucidworks/apollo/pipeline/Context.html): used to pass variables between stages
* `doc`. [PipelineDocument](https://javadoc.lucidworks.com/fusion-pipeline-javadocs/5.9/com/lucidworks/apollo/common/pipeline/PipelineDocument.html): Fusion internal representation of a Solr Document. Please note that if you change this class in ways that affect the serialized form (adding fields, for example) you need to change the deserialization code in `GenericJSONDocumentMessageReader`.
The format required is ``.
## Query pipeline stage template expression variables
Query stages have the following variables available:
* `ctx`. [Context](https://javadoc.lucidworks.com/fusion-pipeline-javadocs/5.9/com/lucidworks/apollo/pipeline/Context.html): used to pass variables between stages
* `reqResp`. [QueryRequestAndResponse](https://javadoc.lucidworks.com/fusion-pipeline-javadocs/5.9/com/lucidworks/apollo/pipeline/query/QueryRequestAndResponse.html): deserializes pre-request parameters and makes them available
The format required is ``.
## Example
Check that a query has an `fq` filter on a given field for a given value:
In the UI, set property name to `ids` and Property Value to `req.hasParam("fq")`
## Messaging services template expression variables
Messages have a set of variables which correspond to the parts of a system message:
* id
* to
* from
* subject
* body
* type
* schedule
A system message is the result of evaluating the following expression:
```xml wrap theme={"dark"}
```
## Messaging services template expression variables
Messages have a set of variables which correspond to the parts of a system message:
* id
* to
* from
* subject
* body
* type
* schedule
A system message is the result of evaluating the following expression:
```xml wrap theme={"dark"}