Template Expressions
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 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 <foo.bar> 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 <doc.title> evaluates to Star Wars.
Index pipeline stage template expression variables
Index stages have the following variables available:
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ctx. Context: used to pass variables between stages -
doc. PipelineDocument: 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 inGenericJSONDocumentMessageReader.
The format required is <request.q>.
Query pipeline stage template expression variables
Query stages have the following variables available:
-
ctx. Context: used to pass variables between stages -
reqResp. QueryRequestAndResponse: deserializes pre-request parameters and makes them available
The format required is <request.q>.
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:
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id
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to
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from
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subject
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body
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type
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schedule
A system message is the result of evaluating the following expression:
<id><to><from><subject><body><type><schedule>