Simple

Since Camel 1.1

The Simple Expression Language was a really simple language when it was created, but has since grown more powerful. It is primarily intended for being a very small and simple language for evaluating Expression or Predicate without requiring any new dependencies or knowledge of other scripting languages such as Groovy.

The simple language is designed with intent to cover almost all the common use cases when little need for scripting in your Camel routes.

However, for much more complex use cases, then a more powerful language is recommended such as:

The simple language requires camel-bean JAR as classpath dependency if the simple language uses OGNL expressions, such as calling a method named myMethod on the message body: ${body.myMethod()}. At runtime the simple language will then us its built-in OGNL support which requires the camel-bean component.

The simple language uses ${body} placeholders for complex expressions or functions.

See also the CSimple language which is compiled.

Alternative syntax

You can also use the alternative syntax which uses $simple{ } as placeholders. This can be used in situations to avoid clashes when using, for example, Spring property placeholder together with Camel.

Simple Language options

The Simple language supports 2 options, which are listed below.

Name Default Java Type Description

Name	Default	Java Type	Description
resultType (common)		`String`	Sets the class of the result type (type from output).
trim (advanced)	`true`	`Boolean`	Whether to trim the value to remove leading and trailing whitespaces and line breaks.

resultType (common)

String

Sets the class of the result type (type from output).

trim (advanced)

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

Variables

Variable Type Description

Variable	Type	Description
camelId	String	the CamelContext name
camelContext.OGNL	Object	the CamelContext invoked using a Camel OGNL expression.
exchange	Exchange	the Exchange
exchange.OGNL	Object	the Exchange invoked using a Camel OGNL expression.
exchangeId	String	the exchange id
id	String	the message id
logExchange	String	Dumps the exchange for logging purpose (uses `ExchangeFormatter` to format the output).
messageTimestamp	long	the message timestamp (millis since epoc) that this message originates from. Some systems like JMS, Kafka, AWS have a timestamp on the event/message that Camel received. This method returns the timestamp if a timestamp exists. The message timestamp and exchange created are different. An exchange always has a created timestamp which is the local timestamp when Camel created the exchange. The message timestamp is only available in some Camel components when the consumer is able to extract the timestamp from the source event. If the message has no timestamp, then 0 is returned.
body	Object	the body
body.OGNL	Object	the body invoked using a Camel OGNL expression.
bodyAs(type)	Type	Converts the body to the given type determined by its classname. The converted body can be null.
bodyAs(type).OGNL	Object	Converts the body to the given type determined by its classname and then invoke methods using a Camel OGNL expression. The converted body can be null.
bodyOneLine	String	Converts the body to a String and removes all line-breaks, so the string is in one line.
prettyBody	String	Converts the body to a String, and attempts to pretty print if JSon or XML; otherwise the body is returned as the String value.
originalBody	Object	The original incoming body (only available if allowUseOriginalMessage=true).
mandatoryBodyAs(type)	Type	Converts the body to the given type determined by its classname, and expects the body to be not null.
mandatoryBodyAs(type).OGNL	Object	Converts the body to the given type determined by its classname and then invoke methods using a Camel OGNL expression.
header.foo	Object	refer to the foo header
header[foo]	Object	refer to the foo header
headers.foo	Object	refer to the foo header
headers:foo	Object	refer to the foo header
headers[foo]	Object	refer to the foo header
header.foo[bar]	Object	regard foo header as a map and perform lookup on the map with bar as the key
header.foo.OGNL	Object	refer to the foo header and invoke its value using a Camel OGNL expression.
headerAs(key,type)	Type	converts the header to the given type determined by its classname
headers	Map	refer to the headers
headers.size	int	The number of headers
variable.foo	Object	refer to the foo variable
variable[foo]	Object	refer to the foo variable
variable.foo.OGNL	Object	refer to the foo variable and invoke its value using a Camel OGNL expression.
variableAs(key,type)	Type	converts the variable to the given type determined by its classname
variables	Map	refer to the variables
variables.size	int	The number of variables
exchangeProperty.foo	Object	refer to the foo property on the exchange
exchangeProperty[foo]	Object	refer to the foo property on the exchange
exchangeProperty.foo.OGNL	Object	refer to the foo property on the exchange and invoke its value using a Camel OGNL expression.
messageAs(type)	Type	Converts the message to the given type determined by its classname. The converted message can be null.
messageAs(type).OGNL	Object	Converts the message to the given type determined by its classname and then invoke methods using a Camel OGNL expression. The converted message can be null.
sys.foo	String	refer to the JVM system property
sysenv.foo	String	refer to the system environment variable
env.foo	String	refer to the system environment variable
exception	Object	refer to the exception object on the exchange, is null if no exception set on exchange. Will fall back and grab caught exceptions (`Exchange.EXCEPTION_CAUGHT`) if the Exchange has any.
exception.OGNL	Object	refer to the exchange exception invoked using a Camel OGNL expression object
exception.message	String	refer to the `exception.message` on the exchange, is null if no exception set on exchange. Will fall back and grab caught exceptions (`Exchange.EXCEPTION_CAUGHT`) if the Exchange has any.
exception.stacktrace	String	refer to the exception.stracktrace on the exchange, is null if no exception set on exchange. Will fall back and grab caught exceptions (`Exchange.EXCEPTION_CAUGHT`) if the Exchange has any.
date:_command_	Date	evaluates to a Date object. Supported commands are: `now` for current timestamp, `exchangeCreated` for the timestamp when the current exchange was created, `header.xxx` to use the Long/Date object in the header with the key xxx. `variable.xxx` to use the Long/Date in the variable with the key xxx. `exchangeProperty.xxx` to use the Long/Date object in the exchange property with the key xxx. `file` for the last modified timestamp of the file (available with a File consumer). Command accepts offsets such as: `now-24h` or `header.xxx+1h` or even `now+1h30m-100`.
date:_command:pattern_	String	Date formatting using `java.text.SimpleDateFormat` patterns.
date-with-timezone:_command:timezone:pattern_	String	Date formatting using `java.text.SimpleDateFormat` timezones and patterns.
bean:_bean expression_	Object	Invoking a bean expression using the Bean language. Specifying a method name, you must use dot as the separator. We also support the ?method=methodname syntax that is used by the Bean component. Camel will by default lookup a bean by the given name. However, if you need to refer to a bean class (such as calling a static method), then you can prefix with the type, such as `bean:type:fqnClassName`.
properties:key:default	String	Lookup a property with the given key. If the key does not exist nor has a value, then an optional default value can be specified.
propertiesExist:key	boolean	Checks whether a property placeholder with the given key exists or not. The result can be negated by prefixing the key with `!`.
fromRouteId	String	Returns the original route id where this exchange was created.
routeId	String	Returns the route id of the current route the Exchange is being routed.
routeGroup	String	Returns the route group of the current route the Exchange is being routed. Not all routes have a group assigned, so this may be null.
stepId	String	Returns the id of the current step the Exchange is being routed.
threadId	String	Returns the id of the current thread. Can be used for logging.
threadName	String	Returns the name of the current thread. Can be used for logging.
hostname	String	Returns the local hostname (may be empty if not possible to resolve).
ref:xxx	Object	To look up a bean from the Registry with the given id.
type:name.field	Object	To refer to a type or field by its FQN name. To refer to a field, you can append .FIELD_NAME. For example, you can refer to the constant field from Exchange as: `org.apache.camel.Exchange.FILE_NAME`
empty(type)	depends on parameter	Creates a new empty object of the type given as parameter. The type-parameter-Strings are case-insensitive. `string` → empty String `list` → empty ArrayList `map` → empty HashMap
null	null	represents a null
random(value)	Integer	returns a random Integer between 0 (included) and value (excluded)
random(min,max)	Integer	returns a random Integer between min (included) and max (excluded)
replace(from,to)	String	replace all the string values in the message body. To make it easier to replace single and double quotes, then you can use XML escaped values `"` as double quote, `'` as single quote, and `∅` as empty value.
replace(from,to,exp)	String	replace all the string values in the given expression. To make it easier to replace single and double quotes, then you can use XML escaped values `"` as double quote, `'` as single quote, and `∅` as empty value.
substring(num1)	String	returns a substring of the message body. If the number is positive, then the returned string is clipped from the beginning. If the number is negative, then the returned string is clipped from the ending.
substring(num1,num2)	String	returns a substring of the message body. If the number is positive, then the returned string is clipped from the beginning. If the number is negative, then the returned string is clipped from the ending.
substring(num1,num2,exp)	String	returns a substring of the given expression. If the number is positive, then the returned string is clipped from the beginning. If the number is negative, then the returned string is clipped from the ending.
collate(group)	List	The collate function iterates the message body and groups the data into sub lists of specified size. This can be used with the Splitter EIP to split a message body and group/batch the split sub message into a group of N sub lists. This method works similar to the collate method in Groovy.
skip(number)	Iterator	The skip function iterates the message body and skips the first number of items. This can be used with the Splitter EIP to split a message body and skip the first N number of items.
join(separator,prefix,exp)	String	The join function iterates the message body (by default) and joins the data into a string. The separator is by default a comma. The prefix is optional. The join uses the message body as source by default. It is possible to refer to another source (simple language) such as a header via the exp parameter. For example `join('&','id=','$\{header.ids}')`.
messageHistory	String	The message history of the current exchange - how it has been routed. This is similar to the route stack-trace message history the error handler logs in case of an unhandled exception.
messageHistory(false)	String	As messageHistory but without the exchange details (only includes the route stack-trace). This can be used if you do not want to log sensitive data from the message itself.
uuid(type)	String	Returns a UUID using the Camel `UuidGenerator`. You can choose between `default`, `classic`, `short` and `simple` as the type. If no type is given, the default is used. It is also possible to use a custom `UuidGenerator` and bind the bean to the Registry with an id. For example `${uuid(myGenerator)}` where the ID is myGenerator.
hash(exp,algorithm)	String	Returns a hashed value (string in hex decimal) using JDK MessageDigest. The algorithm can be SHA-256 (default) or SHA3-256.
jsonpath(exp)	Object	When working with JSon data, then this allows using the JsonPath language, for example, to extract data from the message body (in JSon format). This requires having camel-jsonpath JAR on the classpath.
jsonpath(input,exp)	Object	When working with JSon data, then this allows using the JsonPath language, for example, to extract data from the message body (in JSon format). This requires having camel-jsonpath JAR on the classpath. For input, you can choose `header:key`, `exchangeProperty:key` or `variable:key` to use as input for the JSon payload instead of the message body.
jq(exp)	Object	When working with JSon data, then this allows using the JQ language, for example, to extract data from the message body (in JSon format). This requires having camel-jq JAR on the classpath.
jq(input,exp)	Object	When working with JSon data, then this allows using the JQ language, for example, to extract data from the message body (in JSon format). This requires having camel-jq JAR on the classpath. For input, you can choose `header:key`, `exchangeProperty:key` or `variable:key` to use as input for the JSon payload instead of the message body.
xpath(exp)	Object	When working with XML data, then this allows using the XPath language, for example, to extract data from the message body (in XML format). This requires having camel-xpath JAR on the classpath.
xpath(input,exp)	Object	When working with XML data, then this allows using the XPath language, for example, to extract data from the message body (in XML format). This requires having camel-xpath JAR on the classpath. For input you can choose `header:key`, `exchangeProperty:key` or `variable:key` to use as input for the JSon payload instead of the message body.
pretty(exp)	String	Converts the inlined expression to a String, and attempts to pretty print if JSon or XML, otherwise the expression is returned as the String value.
iif(predicate, trueExp, falseExp)	Object	Evaluates the `predicate` expression and returns the value of `trueExp` if the predicate is true, otherwise the value of `falseExp` is returned. This function is similar to the ternary operator in Java.

camelId

String

the CamelContext name

camelContext.OGNL

Object

the CamelContext invoked using a Camel OGNL expression.

exchange

Exchange

the Exchange

exchange.OGNL

Object

the Exchange invoked using a Camel OGNL expression.

exchangeId

String

the exchange id

String

the message id

logExchange

String

Dumps the exchange for logging purpose (uses ExchangeFormatter to format the output).

messageTimestamp

long

the message timestamp (millis since epoc) that this message originates from. Some systems like JMS, Kafka, AWS have a timestamp on the event/message that Camel received. This method returns the timestamp if a timestamp exists. The message timestamp and exchange created are different. An exchange always has a created timestamp which is the local timestamp when Camel created the exchange. The message timestamp is only available in some Camel components when the consumer is able to extract the timestamp from the source event. If the message has no timestamp, then 0 is returned.

body

Object

the body

body.OGNL

Object

the body invoked using a Camel OGNL expression.

bodyAs(type)

Type

Converts the body to the given type determined by its classname. The converted body can be null.

bodyAs(type).OGNL

Object

Converts the body to the given type determined by its classname and then invoke methods using a Camel OGNL expression. The converted body can be null.

bodyOneLine

String

Converts the body to a String and removes all line-breaks, so the string is in one line.

prettyBody

String

Converts the body to a String, and attempts to pretty print if JSon or XML; otherwise the body is returned as the String value.

originalBody

Object

The original incoming body (only available if allowUseOriginalMessage=true).

mandatoryBodyAs(type)

Type

Converts the body to the given type determined by its classname, and expects the body to be not null.

mandatoryBodyAs(type).OGNL

Object

Converts the body to the given type determined by its classname and then invoke methods using a Camel OGNL expression.

header.foo

Object

refer to the foo header

header[foo]

Object

refer to the foo header

headers.foo

Object

refer to the foo header

headers:foo

Object

refer to the foo header

headers[foo]

Object

refer to the foo header

header.foo[bar]

Object

regard foo header as a map and perform lookup on the map with bar as the key

header.foo.OGNL

Object

refer to the foo header and invoke its value using a Camel OGNL expression.

headerAs(key,type)

Type

converts the header to the given type determined by its classname

headers

Map

refer to the headers

headers.size

int

The number of headers

variable.foo

Object

refer to the foo variable

variable[foo]

Object

refer to the foo variable

variable.foo.OGNL

Object

refer to the foo variable and invoke its value using a Camel OGNL expression.

variableAs(key,type)

Type

converts the variable to the given type determined by its classname

variables

Map

refer to the variables

variables.size

int

The number of variables

exchangeProperty.foo

Object

refer to the foo property on the exchange

exchangeProperty[foo]

Object

refer to the foo property on the exchange

exchangeProperty.foo.OGNL

Object

refer to the foo property on the exchange and invoke its value using a Camel OGNL expression.

messageAs(type)

Type

Converts the message to the given type determined by its classname. The converted message can be null.

messageAs(type).OGNL

Object

Converts the message to the given type determined by its classname and then invoke methods using a Camel OGNL expression. The converted message can be null.

sys.foo

String

refer to the JVM system property

sysenv.foo

String

refer to the system environment variable

env.foo

String

refer to the system environment variable

exception

Object

refer to the exception object on the exchange, is null if no exception set on exchange. Will fall back and grab caught exceptions (Exchange.EXCEPTION_CAUGHT) if the Exchange has any.

exception.OGNL

Object

refer to the exchange exception invoked using a Camel OGNL expression object

exception.message

String

refer to the exception.message on the exchange, is null if no exception set on exchange. Will fall back and grab caught exceptions (Exchange.EXCEPTION_CAUGHT) if the Exchange has any.

exception.stacktrace

String

refer to the exception.stracktrace on the exchange, is null if no exception set on exchange. Will fall back and grab caught exceptions (Exchange.EXCEPTION_CAUGHT) if the Exchange has any.

date:_command_

Date

evaluates to a Date object. Supported commands are: now for current timestamp, exchangeCreated for the timestamp when the current exchange was created, header.xxx to use the Long/Date object in the header with the key xxx. variable.xxx to use the Long/Date in the variable with the key xxx. exchangeProperty.xxx to use the Long/Date object in the exchange property with the key xxx. file for the last modified timestamp of the file (available with a File consumer). Command accepts offsets such as: now-24h or header.xxx+1h or even now+1h30m-100.

date:_command:pattern_

String

Date formatting using java.text.SimpleDateFormat patterns.

date-with-timezone:_command:timezone:pattern_

String

Date formatting using java.text.SimpleDateFormat timezones and patterns.

bean:_bean expression_

Object

Invoking a bean expression using the Bean language. Specifying a method name, you must use dot as the separator. We also support the ?method=methodname syntax that is used by the Bean component. Camel will by default lookup a bean by the given name. However, if you need to refer to a bean class (such as calling a static method), then you can prefix with the type, such as bean:type:fqnClassName.

properties:key:default

String

Lookup a property with the given key. If the key does not exist nor has a value, then an optional default value can be specified.

propertiesExist:key

boolean

Checks whether a property placeholder with the given key exists or not. The result can be negated by prefixing the key with !.

fromRouteId

String

Returns the original route id where this exchange was created.

routeId

String

Returns the route id of the current route the Exchange is being routed.

routeGroup

String

Returns the route group of the current route the Exchange is being routed. Not all routes have a group assigned, so this may be null.

stepId

String

Returns the id of the current step the Exchange is being routed.

threadId

String

Returns the id of the current thread. Can be used for logging.

threadName

String

Returns the name of the current thread. Can be used for logging.

hostname

String

Returns the local hostname (may be empty if not possible to resolve).

ref:xxx

Object

To look up a bean from the Registry with the given id.

type:name.field

Object

To refer to a type or field by its FQN name. To refer to a field, you can append .FIELD_NAME. For example, you can refer to the constant field from Exchange as: org.apache.camel.Exchange.FILE_NAME

empty(type)

depends on parameter

Creates a new empty object of the type given as parameter. The type-parameter-Strings are case-insensitive.

string → empty String
list → empty ArrayList
map → empty HashMap

null

represents a null

random(value)

Integer

returns a random Integer between 0 (included) and value (excluded)

random(min,max)

Integer

returns a random Integer between min (included) and max (excluded)

replace(from,to)

String

replace all the string values in the message body. To make it easier to replace single and double quotes, then you can use XML escaped values " as double quote, ' as single quote, and ∅ as empty value.

replace(from,to,exp)

String

replace all the string values in the given expression. To make it easier to replace single and double quotes, then you can use XML escaped values " as double quote, ' as single quote, and ∅ as empty value.

substring(num1)

String

returns a substring of the message body. If the number is positive, then the returned string is clipped from the beginning. If the number is negative, then the returned string is clipped from the ending.

substring(num1,num2)

String

substring(num1,num2,exp)

String

returns a substring of the given expression. If the number is positive, then the returned string is clipped from the beginning. If the number is negative, then the returned string is clipped from the ending.

collate(group)

List

The collate function iterates the message body and groups the data into sub lists of specified size. This can be used with the Splitter EIP to split a message body and group/batch the split sub message into a group of N sub lists. This method works similar to the collate method in Groovy.

skip(number)

Iterator

The skip function iterates the message body and skips the first number of items. This can be used with the Splitter EIP to split a message body and skip the first N number of items.

join(separator,prefix,exp)

String

The join function iterates the message body (by default) and joins the data into a string. The separator is by default a comma. The prefix is optional.

The join uses the message body as source by default. It is possible to refer to another source (simple language) such as a header via the exp parameter. For example join('&','id=','$\{header.ids}').

messageHistory

String

The message history of the current exchange - how it has been routed. This is similar to the route stack-trace message history the error handler logs in case of an unhandled exception.

messageHistory(false)

String

As messageHistory but without the exchange details (only includes the route stack-trace). This can be used if you do not want to log sensitive data from the message itself.

uuid(type)

String

Returns a UUID using the Camel UuidGenerator. You can choose between default, classic, short and simple as the type. If no type is given, the default is used. It is also possible to use a custom UuidGenerator and bind the bean to the Registry with an id. For example ${uuid(myGenerator)} where the ID is myGenerator.

hash(exp,algorithm)

String

Returns a hashed value (string in hex decimal) using JDK MessageDigest. The algorithm can be SHA-256 (default) or SHA3-256.

jsonpath(exp)

Object

jsonpath(input,exp)

Object

When working with JSon data, then this allows using the JsonPath language, for example, to extract data from the message body (in JSon format). This requires having camel-jsonpath JAR on the classpath. For input, you can choose header:key, exchangeProperty:key or variable:key to use as input for the JSon payload instead of the message body.

jq(exp)

Object

When working with JSon data, then this allows using the JQ language, for example, to extract data from the message body (in JSon format). This requires having camel-jq JAR on the classpath.

jq(input,exp)

Object

When working with JSon data, then this allows using the JQ language, for example, to extract data from the message body (in JSon format). This requires having camel-jq JAR on the classpath. For input, you can choose header:key, exchangeProperty:key or variable:key to use as input for the JSon payload instead of the message body.

xpath(exp)

Object

When working with XML data, then this allows using the XPath language, for example, to extract data from the message body (in XML format). This requires having camel-xpath JAR on the classpath.

xpath(input,exp)

Object

When working with XML data, then this allows using the XPath language, for example, to extract data from the message body (in XML format). This requires having camel-xpath JAR on the classpath. For input you can choose header:key, exchangeProperty:key or variable:key to use as input for the JSon payload instead of the message body.

pretty(exp)

String

Converts the inlined expression to a String, and attempts to pretty print if JSon or XML, otherwise the expression is returned as the String value.

iif(predicate, trueExp, falseExp)

Object

Evaluates the predicate expression and returns the value of trueExp if the predicate is true, otherwise the value of falseExp is returned. This function is similar to the ternary operator in Java.

Attachment functions

From Camel 4.10 onwards then Camel has built-in attachment functions making it easy to obtain details from attachments stored on the Camel Message such as from HTTP file uploads, email with file attachments etc.

This requires having camel-attachments JAR on the classpath.

Function Type Description

Function	Type	Description
attachments	Map	All the attachments as a `Map<String,DataHandler>`.
attachments.size	int	The number of attachments. Is 0 if there are no attachments.
attachmentContentAsText(key)	String	The content of the attachment as text (ie `String`).
attachmentContent(key)	Object	The content of the attachment.
attachmentContentAs(key,type)	Object	The content of the attachment, converted to the given type.
attachmentHeader(key,name)	Object	The attachment header with the given name.
attachmentHeaderAs(key,name,type)	Object	The attachment header with the given name, converted to the given type.
attachment[key]	DataHandler	The `DataHandler` for the given attachment.
attachment.OGNL	Object	refer to the foo attachment on the exchange and invoke its value using a Camel OGNL expression.

attachments

Map

All the attachments as a Map<String,DataHandler>.

attachments.size

int

The number of attachments. Is 0 if there are no attachments.

attachmentContentAsText(key)

String

The content of the attachment as text (ie String).

attachmentContent(key)

Object

The content of the attachment.

attachmentContentAs(key,type)

Object

The content of the attachment, converted to the given type.

attachmentHeader(key,name)

Object

The attachment header with the given name.

attachmentHeaderAs(key,name,type)

Object

The attachment header with the given name, converted to the given type.

attachment[key]

DataHandler

The DataHandler for the given attachment.

attachment.OGNL

Object

refer to the foo attachment on the exchange and invoke its value using a Camel OGNL expression.

OGNL expression support

The Simple and Bean languages support a Camel OGNL notation for invoking beans in a chain like fashion.

OGNL (Object-Graph Navigation Language) is a powerful expression language used in Java. In Camel you can use OGNL dot notation to invoke methods. If you for instance have a body that contains a POJO that has a getFamilyName method then you can construct the Simple syntax as follows:

simple("${body.familyName}")

Or use similar syntax as in Java:

simple("${body.getFamilyName()}")

Camel’s OGNL support is for invoking methods only. You cannot access fields. Camel support accessing the length field of Java arrays.

When using OGNL then camel-bean JAR is required to be on the classpath.

OGNL Variables

The following variables support OGNL:

Variable
camelContext
exchange
exception
body
bodyAs(type)
messageAs(type)
header.foo
exchangeProperty.foo
variable.foo

Variable

camelContext

exchange

exception

body

bodyAs(type)

messageAs(type)

header.foo

exchangeProperty.foo

variable.foo

Basic OGNL examples

Suppose the Message IN body contains a POJO which has a getAddress() method. Then you can use Camel OGNL notation to access the address object:

simple("${body.address}")
simple("${body.address.street}")
simple("${body.address.zip}")

Camel understands the shorthand names for getters, but you can invoke any method or use the real name such as:

simple("${body.address}")
simple("${body.getAddress.getStreet}")
simple("${body.address.getZip}")
simple("${body.doSomething}")

You can also use the null safe operator (?.) to avoid NPE if, for example, the body does NOT have an address

simple("${body?.address?.street}")

Advanced OGNL examples

It is also possible to index in Map or List types, so you can do:

simple("${body[foo].name}")

To assume the body is Map based and look up the value with foo as key, and invoke the getName method on that value.

If the key has space, then you must enclose the key with quotes, for example, 'foo bar':

simple("${body['foo bar'].name}")

You can access the Map or List objects directly using their key name (with or without dots) :

simple("${body[foo]}")
simple("${body[this.is.foo]}")

Suppose there was no value with the key foo then you can use the null safe operator to avoid the NPE as shown:

simple("${body[foo]?.name}")

You can also access List types, for example, to get lines from the address you can do:

simple("${body.address.lines[0]}")
simple("${body.address.lines[1]}")
simple("${body.address.lines[2]}")

There is a special last keyword which can be used to get the last value from a list.

simple("${body.address.lines[last]}")

And to get the 2nd last you can subtract a number, so we can use last-1 to indicate this:

simple("${body.address.lines[last-1]}")

And the third last is, of course:

simple("${body.address.lines[last-2]}")

And you can call the size method on the list with

simple("${body.address.lines.size}")

Camel supports the length field for Java arrays as well, e.g.:

String[] lines = new String[]{"foo", "bar", "cat"};
exchange.getIn().setBody(lines);

simple("There are ${body.length} lines")

And yes, you can combine this with the operator support as shown below:

simple("${body.address.zip} > 1000")

Operator support

The parser is limited to only support a single operator.

To enable it, the left value must be enclosed in ${ }. The syntax is:

${leftValue} OP rightValue

Where the rightValue can be a String literal enclosed in ' ', null, a constant value or another expression enclosed in ${ }.

There must be spaces around the operator.

Camel will automatically type convert the rightValue type to the leftValue type, so it is able to e.g., convert a string into a numeric, so you can use > comparison for numeric values.

The following operators are supported:

Operator Description

Operator	Description
==	equals
=~	equals ignore case (will ignore case when comparing String values)
>	greater than
>=	greater than or equals
<	less than
<=	less than or equals
!=	not equals
!=~	not equals ignore case (will ignore case when comparing String values)
contains	For testing if contains in a string-based value
!contains	For testing if it does not contain in a string-based value
~~	For testing if contains by ignoring case sensitivity in a string-based value
!~~	For testing if it does not contain by ignoring case sensitivity in a string-based value
regex	For matching against a given regular expression pattern defined as a String value
!regex	For not matching against a given regular expression pattern defined as a String value
in	For matching if in a set of values, each element must be separated by comma. If you want to include an empty value, then it must be defined using double comma, e.g. `',, bronze,silver,gold'`, which is a set of four values with an empty value and then the three medals.
!in	For matching if not in a set of values, each element must be separated by comma. If you want to include an empty value, then it must be defined using double comma, e.g. `',,bronze,silver,gold'`, which is a set of four values with an empty value and then the three medals.
is	For matching if the left-hand side type is an instance of the value.
!is	For matching if the left-hand side type is not an instance of the value.
range	For matching if the left-hand side is within a range of values defined as numbers: `from..to`..
!range	For matching if the left-hand side is not within a range of values defined as numbers: `from..to`. .
startsWith	For testing if the left-hand side string starts with the right-hand string.
starts with	Same as the startsWith operator.
endsWith	For testing if the left-hand side string ends with the right-hand string.
ends with	Same as the endsWith operator.

equals

equals ignore case (will ignore case when comparing String values)

greater than

greater than or equals

less than

less than or equals

not equals

!=~

not equals ignore case (will ignore case when comparing String values)

contains

For testing if contains in a string-based value

!contains

For testing if it does not contain in a string-based value

For testing if contains by ignoring case sensitivity in a string-based value

!~~

For testing if it does not contain by ignoring case sensitivity in a string-based value

regex

For matching against a given regular expression pattern defined as a String value

!regex

For not matching against a given regular expression pattern defined as a String value

For matching if in a set of values, each element must be separated by comma. If you want to include an empty value, then it must be defined using double comma, e.g. ',, bronze,silver,gold', which is a set of four values with an empty value and then the three medals.

!in

For matching if not in a set of values, each element must be separated by comma. If you want to include an empty value, then it must be defined using double comma, e.g. ',,bronze,silver,gold', which is a set of four values with an empty value and then the three medals.

For matching if the left-hand side type is an instance of the value.

!is

For matching if the left-hand side type is not an instance of the value.

range

For matching if the left-hand side is within a range of values defined as numbers: from..to..

!range

For matching if the left-hand side is not within a range of values defined as numbers: from..to. .

startsWith

For testing if the left-hand side string starts with the right-hand string.

starts with

Same as the startsWith operator.

endsWith

For testing if the left-hand side string ends with the right-hand string.

ends with

Same as the endsWith operator.

And the following unary operators can be used:

Operator Description

Operator	Description
++	To increment a number by one. The left-hand side must be a function, otherwise parsed as literal.
—	To decrement a number by one. The left-hand side must be a function, otherwise parsed as literal.
\n	To use newline character.
\t	To use tab character.
\r	To use carriage return character.
\}	To use the `}` character as text. This may be needed when building a JSon structure with the simple language.

To increment a number by one. The left-hand side must be a function, otherwise parsed as literal.

—

To decrement a number by one. The left-hand side must be a function, otherwise parsed as literal.

To use newline character.

To use tab character.

To use carriage return character.

To use the } character as text. This may be needed when building a JSon structure with the simple language.

And the following logical operators can be used to group expressions:

Operator	Description
&&	The logical and operator is used to group two expressions.
\|\|	The logical or operator is used to group two expressions.

Operator

Description

The logical and operator is used to group two expressions.

The logical or operator is used to group two expressions.

The syntax for AND is:

${leftValue} OP rightValue && ${leftValue} OP rightValue

And the syntax for OR is:

${leftValue} OP rightValue || ${leftValue} OP rightValue

Some examples:

// exact equals match
simple("${header.foo} == 'foo'")

// ignore case when comparing, so if the header has value FOO, this will match
simple("${header.foo} =~ 'foo'")

// here Camel will type convert '100' into the type of header.bar and if it is an Integer '100' will also be converter to an Integer
simple("${header.bar} == '100'")

simple("${header.bar} == 100")

// 100 will be converter to the type of header.bar, so we can do > comparison
simple("${header.bar} > 100")

// if the value of header.bar was 100, value returned will be 101. header.bar itself will not be changed.
simple("${header.bar}++")

Comparing with different types

When you compare with different types such as String and int, then you have to take a bit of care. Camel will use the type from the left-hand side as first priority. And fallback to the right-hand side type if both values couldn’t be compared based on that type.
This means you can flip the values to enforce a specific type. Suppose the bar value above is a String. Then you can flip the equation:

simple("100 < ${header.bar}")

which then ensures the int type is used as first priority.

This may change in the future if the Camel team improves the binary comparison operations to prefer numeric types to String-based. It’s most often the String type which causes problems when comparing with numbers.

// testing for null
simple("${header.baz} == null")

// testing for not null
simple("${header.baz} != null")

And a bit more advanced example where the right value is another expression

simple("${header.date} == ${date:now:yyyyMMdd}")

simple("${header.type} == ${bean:orderService?method=getOrderType}")

And an example with contains, testing if the title contains the word Camel

simple("${header.title} contains 'Camel'")

And an example with regex, testing if the number header is a 4-digit value:

simple("${header.number} regex '\\d{4}'")

And finally an example if the header equals any of the values in the list. Each element must be separated by comma, and no space around.
This also works for numbers etc., as Camel will convert each element into the type of the left-hand side.

simple("${header.type} in 'gold,silver'")

And for all the last 3, we also support the negate test using not:

simple("${header.type} !in 'gold,silver'")

And you can test if the type is a certain instance, e.g., for instance a String

simple("${header.type} is 'java.lang.String'")

We have added a shorthand for all java.lang types, so you can write it as:

simple("${header.type} is 'String'")

Ranges are also supported. The range interval requires numbers and both from and end are inclusive. For instance, to test whether a value is between 100 and 199:

simple("${header.number} range 100..199")

Notice we use .. in the range without spaces. It is based on the same syntax as Groovy.

simple("${header.number} range '100..199'")

As the XML DSL does not have all the power as the Java DSL with all its various builder methods, you have to resort to using some other languages for testing with simple operators. Now you can do this with the simple language. In the sample below, we want to test it if the header is a widget order:

<from uri="seda:orders">
   <filter>
       <simple>${header.type} == 'widget'</simple>
       <to uri="bean:orderService?method=handleWidget"/>
   </filter>
</from>

Using and / or

If you have two expressions you can combine them with the && or || operator.

For instance:

simple("${header.title} contains 'Camel' && ${header.type'} == 'gold'")

And of course the || is also supported. The sample would be:

simple("${header.title} contains 'Camel' || ${header.type'} == 'gold'")

Examples

In the XML DSL sample below, we filter based on a header value:

<from uri="seda:orders">
   <filter>
       <simple>${header.foo}</simple>
       <to uri="mock:fooOrders"/>
   </filter>
</from>

The Simple language can be used for the predicate test above in the Message Filter pattern, where we test if the in message has a foo header (a header with the key foo exists). If the expression evaluates to true, then the message is routed to the mock:fooOrders endpoint, otherwise the message is dropped.

The same example in Java DSL:

from("seda:orders")
    .filter().simple("${header.foo}")
        .to("seda:fooOrders");

You can also use the simple language for simple text concatenations such as:

from("direct:hello")
    .transform().simple("Hello ${header.user} how are you?")
    .to("mock:reply");

Notice that we must use ${ } placeholders in the expression now to allow Camel to parse it correctly.

And this sample uses the date command to output current date.

from("direct:hello")
    .transform().simple("The today is ${date:now:yyyyMMdd} and it is a great day.")
    .to("mock:reply");

And in the sample below, we invoke the bean language to invoke a method on a bean to be included in the returned string:

from("direct:order")
    .transform().simple("OrderId: ${bean:orderIdGenerator}")
    .to("mock:reply");

Where orderIdGenerator is the id of the bean registered in the Registry. If using Spring, then it is the Spring bean id.

If we want to declare which method to invoke on the order id generator bean we must prepend .method name such as below where we invoke the generateId method.

from("direct:order")
    .transform().simple("OrderId: ${bean:orderIdGenerator.generateId}")
    .to("mock:reply");

We can use the ?method=methodname option that we are familiar with the Bean component itself:

from("direct:order")
    .transform().simple("OrderId: ${bean:orderIdGenerator?method=generateId}")
    .to("mock:reply");

You can also convert the body to a given type, for example, to ensure that it is a String you can do:

<transform>
  <simple>Hello ${bodyAs(String)} how are you?</simple>
</transform>

There are a few types which have a shorthand notation, so we can use String instead of java.lang.String. These are: byte[], String, Integer, Long. All other types must use their FQN name, e.g. org.w3c.dom.Document.

It is also possible to look up a value from a header Map:

<transform>
  <simple>The gold value is ${header.type[gold]}</simple>
</transform>

In the code above we look up the header with name type and regard it as a java.util.Map and we then look up with the key gold and return the value. If the header is not convertible to Map, an exception is thrown. If the header with name type does not exist null is returned.

You can nest functions, such as shown below:

<setHeader name="myHeader">
  <simple>${properties:${header.someKey}}</simple>
</setHeader>

Substring

You can use the substring function to more easily clip the message body. For example if the message body contains the following 10 letters ABCDEFGHIJ then:

<setBody>
  <simple>${substring(3)}</simple>
</setBody>

Then the message body after the substring will be DEFGHIJ. If you want to clip from the end instead, then use negative values such as substring(-3).

You can also clip from both ends at the same time such as substring(1,-1) that will clip the first and last character in the String.

If the number is higher than the length of the message body, then an empty string is returned, for example substring(99).

Instead of the message body then a simple expression can be nested as input, for example, using a variable, as shown below:

<setBody>
  <simple>${substring(1,-1,${variable.foo})}</simple>
</setBody>

Replacing double and single quotes

You can use the replace function to more easily replace all single or double quotes in the message body, using the XML escape syntax. This avoids to fiddle with enclosing a double quote or single quotes with outer quotes, that can get confusing to be correct as you may need to escape the quotes as well. So instead you can use the XML escape syntax where double quote is " and single quote is ' (yeah that is the name).

For example, to replace all double quotes with single quotes:

from("direct:order")
  .transform().simple("${replace(&quot; , &apos;)}")
  .to("mock:reply");

And to replace all single quotes with double quotes:

<setBody>
  <simple>${replace(&apos; , &quot;)}</simple>
</setBody>

Or to remove all double quotes:

<setBody>
  <simple>${replace(&quot; , &empty;)}</simple>
</setBody>

Setting the result type

You can now provide a result type to the Simple expression, which means the result of the evaluation will be converted to the desired type. This is most usable to define types such as booleans, integers, etc.

For example, to set a header as a boolean type, you can do:

.setHeader("cool", simple("true", Boolean.class))

And in XML DSL

<setHeader name="cool">
  <!-- use resultType to indicate that the type should be a java.lang.Boolean -->
  <simple resultType="java.lang.Boolean">true</simple>
</setHeader>

Using new lines or tabs in XML DSLs

It is easier to specify new lines or tabs in XML DSLs as you can escape the value now

<transform>
  <simple>The following text\nis on a new line</simple>
</transform>

Leading and trailing whitespace handling

The trim attribute of the expression can be used to control whether the leading and trailing whitespace characters are removed or preserved. The default value is true, which removes the whitespace characters.

<setBody>
  <simple trim="false">You get some trailing whitespace characters.     </simple>
</setBody>

Loading script from external resource

You can externalize the script and have Camel load it from a resource such as "classpath:", "file:", or "http:". This is done using the following syntax: "resource:scheme:location", e.g., to refer to a file on the classpath you can do:

.setHeader("myHeader").simple("resource:classpath:mysimple.txt")