Using Simple expressions

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

Share

Useful and original tips and tricks are always welcome. Inform us to share it with other users by using the form!