Extraction

In Preacher, an “extraction” is a process to extract values from a target such as a response body. Extractions are descripted in jq or XPath.

Grammer

Full Definition

Here is the definition of Extraction as a mapping.

The definition of Extraction Object

Key	Type	Required?	Description	Example
jq	String	?	A jq query.	".foo.bar"
xpath	String	?	A XPath query.	"/foo/nar"
key	String	?	A key of a dictionary.	"key"
multiple	boolean	no	See: Multiple Values	true
cast_to	string	no	See: Casting	"float"

Note

One of jq, xpath or key is required.

There are some options for each extraction method.

For XPath

The definition of options for XPath extraction.

Key	Type	Description	Example
namespaces	Map[String, String]	A namespace mapping from a prefix to a namespace URI.	{"ns": "namespace-uri"}

Note

All namespaces you expect must be specified explicitly.

Note

Use arbitrary prefix for default namespaces, which XPath 1.0 does not support.

Multiple Values

By default, an extraction provides the first of extracted values. When multiple is true, it provides the list of all extracted values.

Casting

Extracted values can be casted by cast_to settings. This feature is useful for XML analysis, which provides only strings even if they are numbers.

Allowed values are:

• int: Cast to an integer.

• float: Cast to a floating point number.

• string: Cast to a string.

Note

Casting does not affect null.

Abbreviation

Ordinary, extractions should be very simple jq queries. In these cases, an extraction can be written in a string, which is equivalent to {"jq": it}.

Content Compatibility

A extraction must be compatible for the content.

Content	jq	xpath	key
JSON (an object)	o	x	o
JSON (not an object)	o	x	x
XML	x	o	x