Using simple expression language in Dovetail

Simple expression are supported by the following components:

• Set Header
• Set Headers
• Filter
• Content Router
• Split

Frequently used headers

Occurrence	Header name	Expression (example)
Sets full message body to a header of your choice	[Random]	${bodyAs(String)}
Adds an attachment to email	Content-Disposition	attachment;filename=text.csv
Specifies the content type of an xml message	Content-Type	text/xml
Specifies the content type of a json message	Content-Type	text/json or application/json
Specifies the content type of a well formed e-mail in HTML format	Content-Type	text/html
Specifies the content type of an e-mail in plain text format	Content-Type	text/plain
Specifies the filename with a timestamp of the message export	CamelFileName	products_${date:now:yyyyMMdd_HHmmssSS}.xml
Specifies the filename without the original extension of the message export	CamelFileName	john_${file:onlyname.noext}.jpg
Replaces a character range in a value of a header with another range	[Random]	${header.HeaderName.replaceAll("A","B")}
Adds a random number to the value of an existing header	[Random]	${header.CamelFileName}_${random(100)}
Adds a Europe/Amsterdam DateTimeNow to a header	[Random]	${date-with-timezone:now:Europe/Amsterdam:yyyy-MM-dd HH:mm:ss}
Determines the length of the message body	[Random]	${bodyAs(String).length}
Trims the value to remove leading and trailing whitespaces and line breaks	[Random]	${header.HeaderName.trim()}
Gets the error message of the exchange	[Random]	${exchangeProperty.CamelExceptionCaught.getMessage()}

Frequently used content filters

Occurrence	Expression (example)
Allows messages to pass through if the header contains a specific character range	${header.HeaderName} contains "A"
Allows messages to pass through if the header contains the same specific character range as an other header has	'${header.Authorization}' == '#{InboundAuthorizationCode}'
Allows messages to pass through if the length of the consumed file is larger than 0 kB	${header.CamelFileLength} > 0
Allows messages to pass through if one header doesn't contain a specific character range and simultaneously another header doesn't contain a specific character range too	${bodyAs(String)} not contains '"data":"UPDATE"' && ${bodyAs(String)} not contains '"data":"INSERT"'
Allows messages to pass through if a message header is empty.	${header.abc} == ""
Allows messages to pass through if a message header is not empty.	${header.abc} != ""
Allows messages to pass through if the body length is larger than 2 characters	${bodyAs(String).length} > 2

Operator support

Things to keep in mind

• To refer a header in the simple expression language use the notation as follows: ${header.headername}
• Enclose a literal string in ' '
• There must be spaces around the operator
• Syntax: ${header} [operator] 'value'
• Dovetail will automatically type convert the value type to the header type, so it is possible to for example, convert a string into a numeric so you can use > comparison for numeric values
• Keep in mind that simple headers are not case sensitive. When a header variable named errormessage is set at an earlier stage, a header variable set to ERRORMESSAGE will update the previously set header variable errormessage and will not create a new header variable.

Frequently used operators

Operator	Description
==	Equals
>	Greater than
>=	Greater than or equals
<	Less than
<=	Less than or equals
!=	Not equals
contains	For testing if contains in a string based value
not contains	For testing if not contains in a string based value
regex	For matching against a given regular expression pattern defined as a String value
not regex	For not matching against a given regular expression pattern defined as a String value
&&	The logical AND operator is used to group two expressions
||	The logical OR operator is used to group two expressions

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