Response Templating
Response headers and bodies, as well as proxy URLs, can optionally be rendered using Handlebars templates. This enables attributes of the request to be used in generating the response e.g. to pass the value of a request ID header as a response header or render an identifier from part of the URL in the response body.
Enabling/disabling response templating #
Response templating is enabled by default in local mode when WireMock is started programmatically, meaning that it will only be applied to stubs that have the response-template
transformer added to them (see below for details).
Templating can be applied globally (without having to explicitly add response-template
) via a startup option:
WireMockServer wm =
new WireMockServer(options().globalTemplating(true));
It can also be disabled completely via a startup option:
WireMockServer wm =
new WireMockServer(options().templatingEnabled(false));
See the command line docs for the standalone equivalents of these parameters.
Response templating can also be disabled on a per-stub basis when using the bodyFileName
element by adding the disableBodyFileTemplating
parameter to the transformerParameters
object in the stub response definition.
{
"request": {
"method": "GET",
"urlPath": "/test"
},
"response": {
"status": 200,
"bodyFileName": "response.json",
"transformerParameters": {
"disableBodyFileTemplating": true
}
}
}
Customising and extending the template engine #
Custom Handlebars helpers can be registered via an extension point. See Adding Template Helpers for details.
Similarly custom model data providers can be registered as extensions. See Adding Template Model Data for details.
Applying templating in local mode #
When templating is enabled in local mode you must add it to each stub to which you require templating to be applied. This is done by adding response-template
to the set of transformers on the response.
Java #
wm.stubFor(get(urlPathEqualTo("/templated"))
.willReturn(aResponse()
.withBody("{{request.path.[0]}}")
.withTransformers("response-template")));
JSON #
{
"request": {
"urlPath": "/templated"
},
"response": {
"body": "{{request.path.[0]}}",
"transformers": ["response-template"]
}
}
Template caching #
All templated fragments (headers, bodies and proxy URLs) are cached in their compiled form for performance, since compilation can be expensive for larger templates.
By default the capacity of this cache is not limited but a limit can be set via the startup options:
WireMockServer wm =
new WireMockServer(options().withMaxTemplateCacheEntries(10000));
See the command line docs for the equivalent configuration setting when running standalone.
Proxying #
Templating also works when defining proxy URLs, e.g.
Java #
wm.stubFor(get(urlPathEqualTo("/templated"))
.willReturn(aResponse()
.proxiedFrom("{{request.headers.X-WM-Proxy-Url}}")
.withTransformers("response-template")));
JSON #
{
"request": {
"urlPath": "/templated"
},
"response": {
"proxyBaseUrl": "{{request.headers.X-WM-Proxy-Url}}",
"transformers": ["response-template"]
}
}
Templated body file #
The body file for a response can be selected dynamically by templating the file path:
Java #
wm.stubFor(get(urlPathMatching("/static/.*"))
.willReturn(ok()
.withBodyFile("files/{{request.pathSegments.[1]}}")));
JSON #
{
"request": {
"urlPathPattern": "/static/.*",
"method": "GET"
},
"response": {
"status": 200,
"bodyFileName": "files/{{request.pathSegments.[1]}}"
}
}
The request model #
The model of the request is supplied to the header and body templates. The following request attributes are available:
request.id
- The unique ID of each request (introduced in WireMock version 3.7.0
)
request.url
- URL path and query
request.path
- URL path. This can be referenced in full or it can be treated as an array of path segments (like below) e.g. request.path.3
. When the path template URL match type has been used you can additionally reference path variables by name e.g. request.path.contactId
.
request.pathSegments.[<n>]
- URL path segment (zero indexed) e.g. request.pathSegments.2
request.query.<key>
- First value of a query parameter e.g. request.query.search
request.query.<key>.[<n>]
- nth value of a query parameter (zero indexed) e.g. request.query.search.5
request.method
- request method e.g. POST
request.host
- hostname part of the URL e.g. my.example.com
request.port
- port number e.g. 8080
request.scheme
- protocol part of the URL e.g. https
request.baseUrl
- URL up to the start of the path e.g. https://my.example.com:8080
request.headers.<key>
- First value of a request header e.g. request.headers.X-Request-Id
request.headers.[<key>]
- Header with awkward characters e.g. request.headers.[$?blah]
request.headers.<key>.[<n>]
- nth value of a header (zero indexed) e.g. request.headers.ManyThings.1
request.cookies.<key>
- First value of a request cookie e.g. request.cookies.JSESSIONID
request.cookies.<key>.[<n>]
- nth value of a request cookie e.g. request.cookies.JSESSIONID.2
request.body
- Request body text (avoid for non-text bodies)
request.bodyAsBase64
- As of WireMock 3.8.0
, the Base64 representation of the request body.
request.multipart
- As of WireMock 3.8.0
, if the request is a multipart request (boolean).
request.parts
- As of WireMock 3.8.0
, the individual parts of a multipart request are exposed via the template model. Each part can be referenced by its name and exposes a number of properties in the template model. For example, a multipart request with a name of text
has the following properties available:
request.parts.text.binary
- if the part is a binary type.request.parts.text.headers.<key>
- first value of a part header -request.parts.text.headers.content-type
request.parts.text.body
- part body as text.request.parts.text.bodyAsBase64
- part body as base64.
Values that can be one or many #
A number of HTTP elements (query parameters, form fields, headers) can be single or multiple valued. The template request model and built-in helpers attempt to make this easy to work with by wrapping these in a “list or single” type that returns the first (and often only) value when no index is specified, but also support index access.
For instance, given a request URL like /multi-query?things=1&things=2&things=3
I can extract the query data in the following ways:
Note
When using the
eq
helper with one-or-many values, it is necessary to use the indexed form, even if only one value is present. The reason for this is that the non-indexed form returns the wrapper type and not a String, and will therefore fail any comparison with another String value.
Getting values with keys containing special characters #
Certain characters have special meaning in Handlebars and therefore can’t be used in key names when referencing values. If you need to access keys containing these characters you can use the lookup
helper, which permits you to pass the key name as a string literal and thus avoid the restriction.
Probably the most common occurrence of this issue is with array-style query parameters, so for instance if your request URLs you’re matching are of the form /stuff?ids[]=111&ids[]=222&ids[]=333
then you can access these values like:
Using transformer parameters #
Parameter values can be passed to the transformer as shown below (or dynamically added to the parameters map programmatically in custom transformers).
Java #
wm.stubFor(get(urlPathEqualTo("/templated"))
.willReturn(aResponse()
.withBody("{{request.path.[0]}}")
.withTransformers("response-template")
.withTransformerParameter("MyCustomParameter", "Parameter Value")));
JSON #
{
"request": {
"urlPath": "/templated"
},
"response": {
"body": "{{request.path.[0]}}",
"transformers": ["response-template"],
"transformerParameters": {
"MyCustomParameter": "Parameter Value"
}
}
}
These parameters can be referenced in template body content using the parameters.
prefix:
Handlebars helpers #
All of the standard helpers (template functions) provided by the Java Handlebars implementation by jknack plus all of the string helpers and the conditional helpers are available e.g.
Number and assignment helpers #
Variable assignment and number helpers are available:
Val helper #
Released in WireMock version 3.6.0
, the val
helper can be used to access values or provide a default if the value is not present. It can also be used to assign a value to a variable much like the assign
helper. The main difference between val
and assign
is that val
will maintain the type of the date being assigned whereas assign
will always assign a string.
XPath helpers #
Additionally some helpers are available for working with JSON and XML.
When the incoming request contains XML, the xPath
helper can be used to extract values or sub documents via an XPath 1.0 expression. For instance, given the XML
<outer>
<inner>Stuff</inner>
</outer>
The following will render “Stuff” into the output:
And given the same XML the following will render <inner>Stuff</inner>
:
As a convenience the soapXPath
helper also exists for extracting values from SOAP bodies e.g. for the SOAP document:
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope/">
<soap:Body>
<m:a>
<m:test>success</m:test>
</m:a>
</soap:Body>
</soap:Envelope>
The following will render “success” in the output:
Using the output of xPath
in other helpers #
Since version 2.27.0 the XPath helper returns collections of node objects rather than a single string, meaning that the result can be used in further helpers.
The returned node objects have the following properties:
name
- the local XML element name.
text
- the text content of the element.
attributes
- a map of the element’s attributes (name: value)
Referring to the node itself will cause it to be printed.
A common use case for returned node objects is to iterate over the collection with the each
helper:
JSONPath helper #
It is similarly possible to extract JSON values or sub documents via JSONPath using the jsonPath
helper. Given the JSON
{
"outer": {
"inner": "Stuff"
}
}
The following will render “Stuff” into the output:
And for the same JSON the following will render { "inner": "Stuff" }
:
Default value can be specified if the path evaluates to null or undefined:
Parse JSON helper #
The parseJson
helper will parse the input into a map-of-maps. It will assign the result to a variable if a name is specified, otherwise the result will be returned.
It can accept the JSON from a block:
Or as a parameter:
Without assigning to a variable:
Date and time helpers #
A helper is present to render the current date/time, with the ability to specify the format (via Java’s SimpleDateFormat) and offset.
Dates can be rendered in a specific timezone (the default is UTC):
Pass epoch
as the format to render the date as UNIX epoch time (in milliseconds), or unix
as the format to render the UNIX timestamp in seconds.
Dates can be parsed using the parseDate
helper:
Dates can be truncated to e.g. first day of month using the truncateDate
helper:
See the full list of truncations here.
Random value helper #
Random strings of various kinds can be generated:
Pick random helper #
A value can be randomly selected from a literal list:
Or from a list passed as a parameter:
Random number helpers #
These helpers produce random numbers of the desired type. By returning actual typed numbers rather than strings we can use them for further work e.g. by doing arithemetic with the math
helper or randomising the bound in a range
.
Random integers can be produced with lower and/or upper bounds, or neither:
Likewise decimals can be produced with or without bounds:
Formatting numbers #
The numberFormat
helper allows you to specify how numbers are printed. It supports a number of predefined formats, custom format strings and various other options including rounding mode, decimal places and locale.
Predefined formats #
numberFormat
supports the following predefined formats:
integer
currency
percent
Predefined formats can be affected by locale, so it’s usually a good idea to explicitly specify this.
For example, to format a decimal number as currency, specifically British pounds:
Output: £123.46
.
Alternatively, if we wanted to output the number as a percentage:
Output: 12,346%
.
Custom format string #
For maximum control over the number format you can specify a format string:
Output: 123.456700
.
See the Java DecimalFormat documentation for details on how to use format strings.
Configuring number of digits #
Separate from the format parameter, the number of digits before and after the decimal place can be bounded using one or more of four parameters: maximumFractionDigits
, minimumFractionDigits
, maximumIntegerDigits
, minimumIntegerDigits
.
Output: 234.567000
.
Disabling grouping #
By default numberFormat
will insert commas, periods etc. per the locale between groups of digits e.g. 1,234.5
.
This behaviour can be disabled with groupingUsed
.
Output: 12345.678
.
Rounding mode #
The roundingMode
parameter affects how numbers will be rounded up or down when it’s necessary to do so.
For instance, to always round down:
Output: 1.23
.
Available rounding modes are:
up
down
half_up
half_down
half_even
ceiling
floor
.
See the Java RoundingMode documentation for the exact meaning of each of these.
Fake data helpers #
This helper produces random fake data of the desired types available in the Data Faker library. Due to the size of this library, this helper has been provided via RandomExtension
.
Math helper #
The math
(or maths, depending where you are) helper performs common arithmetic operations. It can accept integers, decimals or strings as its operands and will always yield a number as its output rather than a string.
Addition, subtraction, multiplication, division and remainder (mod) are supported:
Range helper #
The range
helper will produce an array of integers between the bounds specified:
This can be usefully combined with randomInt
and each
to output random length, repeating pieces of content e.g.
Array literal helper #
The array
helper will produce an array from the list of parameters specified. The values can be any valid type. Providing no parameters will result in an empty array.
Array add & remove helpers #
As of WireMock version 3.6.0
, the arrayAdd
and arrayRemove
helpers can be used to add or remove elements from an array based on a position value or the start
or end
keywords. If no position is specified, the element will be added or removed from the end of the array.
arrayJoin helper #
Released in WireMock version 3.6.0
, the arrayJoin
helper will concatenate the values passed to it with the separator specified:
You can also specify a prefix
and suffix
to be added to the start and end of the result:
The arrayJoin
helper can also be used as a block helper:
Contains helper #
The contains
helper returns a boolean value indicating whether the string or array passed as the first parameter contains the string passed in the second.
It can be used as parameter to the if
helper:
Or as a block element on its own:
Matches helper #
The matches
helper returns a boolean value indicating whether the string passed as the first parameter matches the regular expression passed in the second:
Like the contains
helper it can be used as parameter to the if
helper:
Or as a block element on its own:
String trim helper #
Use the trim
helper to remove whitespace from the start and end of the input:
Base64 helper #
The base64
helper can be used to base64 encode and decode values:
URL encoding helper #
The urlEncode
helper can be used to URL encode and decode values:
Form helper #
The formData
helper parses its input as an HTTP form, returning an object containing the individual fields as attributes. The helper takes the input string and variable name as its required parameters, with an optional urlDecode
parameter indicating that values should be URL decoded. The folowing example will parse the request body as a form, then output a single field formField3
:
If the form submitted has multiple values for a given field, these can be accessed by index:
Regular expression extract helper #
The regexExtract
helper supports extraction of values matching a regular expresson from a string.
A single value can be extracted like this:
Regex groups can be used to extract multiple parts into an object for later use (the last parameter is a variable name to which the object will be assigned):
Optionally, a default value can be specified for when there is no match. When the regex does not match and no default is specified, an error will be thrown instead.
Size helper #
The size
helper returns the size of a string, list or map:
Hostname helper #
The local machine’s hostname can be printed:
System property helper #
Environment variables and system properties can be printed:
Since 3.5 a default value can be supplied:
If you want to add permitted extensions to your rule, then you can use the ResponseTemplateTransformer
when constructing the response template extension.
The ResponseTemplateTransformer
accepts four arguments:
- The
TemplateEngine
- If templating can be applied globally
- The
FileSource
which is a list of files that can be used for relative references in stub definitions - A list of
TemplateModelDataProviderExtension
objects which are additional metadata providers which will be injected into the model and consumed in the downstream resolution if needed
@Rule
public WireMockRule wm = new WireMockRule(options()
.dynamicPort()
.withRootDirectory(defaultTestFilesRoot())
.extensions(new ResponseTemplateTransformer(
getTemplateEngine(),
options.getResponseTemplatingGlobal(),
getFiles(),
templateModelProviders
)
)
);
The regular expressions are matched in a case-insensitive manner. If no permitted system key patterns are set, a single default of wiremock.*
will be used.