Reference: Studio MVEL Auto-Conversion Syntax Samples

Function	Sample Expression	Description
Auto-convert a string to a variable.	vars['fred'] = '<hello>world</hello>'	Creates a new variable called fred with the content <hello>world</hello> . Use this method to create small messages only. Using expressions to create large strings can lead to poor performance. In most cases, you should use the write step to create content for a variable.
Supply content and MIME type information to a variable.	vars['fred'] = [ 'Hello World', 'text/plain' ]	Creates a new variable called fred with the content Hello World and MIME type text/plain . Use this method to create small messages only. Using expressions to create large strings can lead to poor performance. In most cases, you should use the write step to create content for a variable and configure the MIME type.
Copy from an attachment to a variable.	vars['fred'] = parts[1]	Creates a new variable fred from the first attachment of the current message. In most cases, you should use the copy step to take input from an attachment.
Copy from a message to a variable.	vars['fred'] = message	Creates a new variable fred from the entire message. In most cases, you should use the copy step to take input from the current message.
Supply content and MIME type information to a variable whose value is an expression.	vars['fred'] = [23 + 5, 'text/plain']	Creates a new variable called fred with content 28 and MIME type text/plain .
Create a variable from an XPath fragment in the message root part.	vars['fred'] = parts[0].xpathF('/dink/donk')	Creates a new variable called fred with an XPath fragment from the root part of the current message. Use this method to create small messages only. Using XPath expressions to create large strings can lead to poor performance.
Nullify a variable.	vars['fred'] = null	Removes the variable called fred .
Assign content to the root part.	parts[0] = '<hello>world</hello>'	Assigns the content <hello>world</hello> to the root part. Use this method to create small messages only. Using expressions to create large strings can lead to poor performance. In most cases, you should use the write step to assign content to an attachment and configure the MIME type.
Assign content to the first attachment.	parts[1] = [ 'Hello World', 'text/plain']	Assigns the content Hello World and MIME type of text/plain to the first attachment. Use this method to create small messages only. Using expressions to create large strings can lead to poor performance. In most cases, you should use the write step to assign content to an attachment and configure the MIME type.
Assign content to the root attachment and specify the MIME type.	parts[0] = [ 23 + 5, 'text/plain']	Assigns root part with content 28 and MIME type text/plain .
Assign content from a variable to the message part.	parts[0] = vars['fred']	Assigns the content of the variable fred to a message part. In most cases, you should use the copy step to take input from a variable and assign it to a message part.
Remove the root part.	parts[0] = null	Removes the root part.
Copy an attachment.	parts[2] = parts[1]	Copies the first attachment into a second attachment. In most cases, you should use the copy step to take input from one attachment and assign it to another.
Create a new message with the default MIME type.	context.message = '<hello>world</hello>'	Creates a new message <hello>world</hello> with a default MIME type of text/xml . In most cases, you should use the write step to create a new message.
Create a new message with MIME type of text/plain .	context.message = [ 'Hello World', 'text/plain' ]	Creates a new message Hello World with a MIME type of text/plain . In most cases, you should use the write step to create a new message.
Create a new message from variable content.	context.message = vars['fred']	Creates a new message with the same content and MIME type as the variable fred . In most cases, you should use the copy step to create a new message from a variable.
Create a new message from the root part of the current message.	context.message = parts[0]	Creates a new message from the root part of the current message. In most cases, you should use the copy step to create a new message from a message part.

Auto-convert a string to a variable.

vars['fred'] = '<hello>world</hello>'

Creates a new variable called

fred

with the content

<hello>world</hello>

.

Use this method to create small messages only. Using expressions to create large strings can lead to poor performance.

In most cases, you should use the

write

step to create content for a variable.

Supply content and MIME type information to a variable.

vars['fred'] = [ 'Hello World', 'text/plain' ]

Creates a new variable called

fred

with the content

Hello World

and MIME type

text/plain

.

Use this method to create small messages only. Using expressions to create large strings can lead to poor performance.

In most cases, you should use the

write

step to create content for a variable and configure the MIME type.

Copy from an attachment to a variable.

vars['fred'] = parts[1]

Creates a new variable

fred

from the first attachment of the current message.

In most cases, you should use the

copy

step to take input from an attachment.

Copy from a message to a variable.

vars['fred'] = message

Creates a new variable

fred

from the entire message.

In most cases, you should use the

copy

step to take input from the current message.

Supply content and MIME type information to a variable whose value is an expression.

vars['fred'] = [23 + 5, 'text/plain']

Creates a new variable called

fred

with content

28

and MIME type

text/plain

.

Create a variable from an XPath fragment in the message root part.

vars['fred'] = parts[0].xpathF('/dink/donk')

Creates a new variable called

fred

with an XPath fragment from the root part of the current message.

Use this method to create small messages only. Using XPath expressions to create large strings can lead to poor performance.

Nullify a variable.

vars['fred'] = null

Removes the variable called

fred

.

Assign content to the root part.

parts[0] = '<hello>world</hello>'

Assigns the content

<hello>world</hello>

to the root part.

Use this method to create small messages only. Using expressions to create large strings can lead to poor performance.

In most cases, you should use the

write

step to assign content to an attachment and configure the MIME type.

Assign content to the first attachment.

parts[1] = [ 'Hello World', 'text/plain']

Assigns the content

Hello World

and MIME type of

text/plain

to the first attachment.

Use this method to create small messages only. Using expressions to create large strings can lead to poor performance.

In most cases, you should use the

write

step to assign content to an attachment and configure the MIME type.

Assign content to the root attachment and specify the MIME type.

parts[0] = [ 23 + 5, 'text/plain']

Assigns root part with content

28

and MIME type

text/plain

.

Assign content from a variable to the message part.

parts[0] = vars['fred']

Assigns the content of the variable

fred

to a message part.

In most cases, you should use the

copy

step to take input from a variable and assign it to a message part.

Remove the root part.

parts[0] = null

Removes the root part.

Copy an attachment.

parts[2] = parts[1]

Copies the first attachment into a second attachment.

In most cases, you should use the

copy

step to take input from one attachment and assign it to another.

Create a new message with the default MIME type.

context.message = '<hello>world</hello>'

Creates a new message

<hello>world</hello>

with a default MIME type of

text/xml

.

In most cases, you should use the

write

step to create a new message.

Create a new message with MIME type of

text/plain

.

context.message = [ 'Hello World', 'text/plain' ]

Creates a new message

Hello World

with a MIME type of

text/plain

.

In most cases, you should use the

write

step to create a new message.

Create a new message from variable content.

context.message = vars['fred']

Creates a new message with the same content and MIME type as the variable

fred

.

In most cases, you should use the

copy

step to create a new message from a variable.

Create a new message from the root part of the current message.

context.message = parts[0]

Creates a new message from the root part of the current message.

In most cases, you should use the

copy

step to create a new message from a message part.