code192 Data Integration Tool Expression Language Guide
Overview
All data in code192 Data Integration Tool is represented by an abstraction called a FlowFile. A FlowFile is comprised of two major pieces: content and attributes. The content portion of the FlowFile represents the data on which to operate. For instance, if a file is picked up from a local file system using the GetFile Processor, the contents of the file will become the contents of the FlowFile.
The attributes portion of the FlowFile represents information about the data
itself, or metadata. Attributes are key-value pairs that represent what is
known about the data as well as information that is useful for routing and
processing the data appropriately.
Keeping with the example of a file that is picked up from
a local file system, the FlowFile would have an attribute called filename that
reflected the name of the file on the file system. Additionally, the FlowFile will
have a path attribute that reflects the directory on the file system that this
file lived in. The FlowFile will also have an attribute named uuid, which is a
unique identifier for this FlowFile. For complete listing of the core attributes
check out the FlowFile section of the Developer’s Guide.
However, placing these attributes on a FlowFile do not provide much benefit if the user is unable to make use of them. The Data Integration Tool Expression Language provides the ability to reference these attributes, compare them to other values, and manipulate their values.
Structure of a Data Integration Tool Expression
The Data Integration Tool Expression Language always begins with the start delimiter ${ and ends
with the end delimiter }. Between the start and end delimiters is the text of the
Expression itself. In its most basic form, the Expression can consist of just an
attribute name. For example, ${filename} will return the value of the “filename”
attribute.
In a slightly more complex example, we can instead return a manipulation of this value.
We can, for example, return an all upper-case version of the filename by calling the
toUpper function: ${filename:toUpper()}. In this case, we reference the “filename”
attribute and then manipulate this value by using the toUpper function. A function call
consists of 5 elements. First, there is a function call delimiter :. Second is the name
of the function - in this case, “toUpper”. Next is an open parenthesis ((), followed
by the function arguments. The arguments necessary are dependent upon which function
is being called. In this example, we are using the toUpper function, which does not
have any arguments, so this element is omitted. Finally, the closing parenthesis ())
indicates the end of the function call. There are many different functions that are supported
by the Expression Language to achieve many different goals. Some functions provide String (text)
manipulation, such as the toUpper function. Others, such as the equals and matches functions,
provide comparison functionality. Functions also exist for manipulating dates and times and
for performing mathematical operations. Each of these functions is described below, in the
Functions section, with an explanation of what the function does, the arguments that it
requires, and the type of information that it returns.
When we perform a function call on an attribute, as above, we refer to the attribute as the
subject of the function, as the attribute is the entity on which the function is operating.
We can then chain together multiple function calls, where the return value of the first function
becomes the subject of the second function and its return value becomes the subject of the third
function and so on. Continuing with our example, we can chain together multiple functions by using
the expression ${filename:toUpper():equals('HELLO.TXT')}. There is no limit to the number of
functions that can be chained together.
Any FlowFile attribute can be referenced using the Expression Language. However, if the attribute name contains a “special character,” the attribute name must be escaped by quoting it. The following characters are each considered “special characters”:
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$ (dollar sign)
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| (pipe)
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{ (open brace)
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} (close brace)
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( (open parenthesis)
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) (close parenthesis)
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[ (open bracket)
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] (close bracket)
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, (comma)
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: (colon)
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; (semicolon)
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/ (forward slash)
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* (asterisk)
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' (single quote)
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(space)
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\t (tab)
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\r (carriage return)
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\n (new-line)
Additionally, a number is considered a “special character” if it is the first character of the attribute name.
If any of these special characters is present in an attribute is quoted by using either single or double quotes.
The Expression Language allows single quotes and double quotes to be used interchangeably. For example, the following
can be used to escape an attribute named “my attribute”: ${"my attribute"} or ${'my attribute'}.
In this example, the value to be returned is the value of the "my attribute" value, if it exists. If that attribute
does not exist, the Expression Language will then look for a System Environment Variable named "my attribute." If
unable to find this, it will look for a JVM System Property named "my attribute." Finally, if none of these exists,
the Expression Language will return a null value.
There also exist some functions that expect to have no subject. These functions are invoked simply
by calling the function at the beginning of the Expression, such as ${hostname()}. These functions
can then be changed together, as well. For example, ${hostname():toUpper()}. Attempting to
evaluate the function with subject will result in an error. In the Functions
section below, these functions will clearly indicate in their descriptions that they do not
require a subject.
Often times, we will need to compare the values of two different attributes to each other.
We are able to accomplish this by using embedded Expressions. We can, for example, check if
the “filename” attribute is the same as the “uuid” attribute: ${filename:equals( ${uuid} )}.
Notice here, also, that we have a space between the opening parenthesis for the equals method and
the embedded Expression. This is not necessary and does not affect how the Expression is evaluated
in any way. Rather, it is intended to make the Expression easier to read. White space is ignored by
the Expression Language between delimiters. Therefore, we can use the Expression
${ filename : equals(${ uuid}) } or ${filename:equals(${uuid})} and both Expressions
mean the same thing. We cannot, however, use ${file name:equals(${uuid})}, because this results
in file and name being interpreted as different tokens, rather than a single token, filename.
Expression Language in the Application
The Expression Language is used heavily throughout the Data Integration Tool application for configuring Processor properties. Not all Processor properties support the Expression Language, however. Whether or not a Property supports the Expression Language is determined by the developer of the Processor when the Processor is written. However, the application strives to clearly illustrate for each Property whether or not the Expression Language is supported.
In the application, when configuring a Processor property, the User Interface provides an Information
icon (
) next to the name of the Property. Hovering over this icon with the mouse will provide a tooltip that
provides helpful information about the Property. This information includes a description of the Property,
the default value (if any), historically configured values (if any), and whether or not this Property
supports the expression language.
Expression Language Editor
When configuring the value of a Processor property, the Data Integration Tool User Interface provides help with the
Expression Language using the Expression Language editor. Once an Expression is begin by typing ${,
the editor begins to highlight parentheses and braces so that the user is easily able to tell which
opening parenthesis or brace matches which closing parenthesis or brace.
The editor also supplies context-sensitive help by providing a list of all functions that can be used
at the current cursor position. To activate this feature, press Ctrl+Space on the keyboard. The user
is also able to type part of a function name and then press Ctrl+Space to see all functions that can
be used that start with the same prefix. For example, if we type into the editor ${filename:to
and then press Ctrl+Space, we are provided a pop-up that lists six different functions: toDate,
toLower, toNumber, toRadix, toString, and toUpper. We can then continue typing to narrow
which functions are shown, or we can select one of the functions from the list by double-clicking
it with the mouse or using the arrow keys to highlight the desired function and pressing Enter.
Functions
Functions provide a convenient way to manipulate and compare values of attributes. The Expression Language provides many different functions to meet the needs of a automated dataflow. Each function takes zero or more arguments and returns a single value. These functions can then be chained together to create powerful Expressions to evaluate conditions and manipulate values. See Structure of a Data Integration Tool Expression for more information on how to call and chain functions together.
Data Types
Each argument to a function and each value returned from a function has a specific data type. The Expression Language supports four different data types:
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String: A String is a sequence of characters that can consist of numbers, letters, white space, and special characters.
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Number: A Number is an integer comprised of one or more digits (
0through9). The Expression Language does not provide support for fractional numbers. When converting to numbers from Date data types, they are represented as the number of milliseconds since midnight GMT on January 1, 1970. -
Date: A Date is an object that holds a Date and Time. Utilizing the Date Manipulation and Type Coercion functions this data type can be converted to/from Strings and numbers. If the whole Expression Language expression is evaluated to be a date then it will be converted to a String with the format: "<Day of Week> <Month> <Day of Month> <Hour>:<Minute>:<Second> <Time Zone> <Year>". Also expressed as "E MMM dd HH:mm:ss z yyyy" in Java SimpleDateFormat format. For example: "Wed Dec 31 12:00:04 UTC 2016".
-
Boolean: A Boolean is one of either
trueorfalse.
All attributes are considered to be of type String.
The Expression Language is generally able to automatically coerce a value of one data type to the appropriate data type for a function. However, functions do exist to manually coerce a value into a specific data type. See the Type Coercion section for more information.
Boolean Logic
One of the most powerful features of the Expression Language is the ability to compare an attribute value against some other value. This is used often, for example, to configure how a Processor should route data. The following functions are used for performing boolean logic, such as comparing two values. Each of these functions returns a value of type Boolean.
isNull
Description: The isNull function returns true if the subject is null, false otherwise. This is typically used to determine
if an attribute exists.
Subject Type: Any
Arguments: No arguments
Return Type: Boolean
Examples: ${filename:isNull()} returns true if the "filename" attribute does not exist.
It returns false if the attribute exists.
notNull
Description: The notNull function returns the opposite value of the isNull function. That is, it will return true if the
subject exists and false otherwise.
Subject Type: Any
Arguments: No arguments
Return Type: Boolean
Examples: ${filename:notNull()} returns true if the "filename" attribute exists. It returns false if the attribute
does not exist.
isEmpty
Description: The isEmpty function returns true if the Subject is null or contains only white-space
(new line, carriage return, space, tab), false otherwise.
Subject Type: String
Arguments: No arguments
Return Type: Boolean
Examples: ${filename:isEmpty()} returns true if the "filename" attribute does not exist or contains only
white space.
equals
Description: The equals function is very widely used and determines if its subject is equal to another String value.
Note that the equals function performs a direct comparison of two String values. Take care not to confuse this
function with the matches function, which evaluates its subject against a Regular Expression.
Subject Type: Any
Arguments:
-
value : The value to compare the Subject to. Must be same type as the Subject.
Return Type: Boolean
Examples:
We can check if the filename of a FlowFile is "hello.txt" by using the expression ${filename:equals('hello.txt')},
or we could check if the value of the attribute hello is equal to the value of the filename attribute:
${hello:equals( ${filename} )}.
equalsIgnoreCase
Description: Similar to the equals function, the equalsIgnoreCase function compares its subject against a String value but returns
true if the two values differ only by case (upper case vs. lower case).
Subject Type: String
Arguments:
-
value : The value to compare the Subject to.
Return Type: Boolean
Examples: ${filename:equalsIgnoreCase('hello.txt')} will evaluate to true if filename is equal to "hello.txt"
or "HELLO.TXT" or "HeLLo.TxT".
gt
Description: The gt function is used for numeric comparison and returns true if the subject is Greater Than
its argument. If either the subject or the argument cannot be coerced into a Number,
this function returns false.
Subject Type: Number
Arguments:
-
value : The number to compare the Subject to.
Return Type: Boolean
Examples: ${fileSize:gt( 1024 )} will return true if the size of the FlowFile’s content is more than 1 kilobyte
(1024 bytes). Otherwise, it will return false.
ge
Description: The ge function is used for numeric comparison and returns true if the subject is Greater Than
Or Equal To its argument. If either the subject or the argument cannot be coerced into a Number,
this function returns false.
Subject Type: Number
Arguments:
-
value : The number to compare the Subject to.
Return Type: Boolean
Examples: ${fileSize:ge( 1024 )} will return true if the size of the FlowFile’s content is at least (
is greater than or equal to) 1 kilobyte (1024 bytes). Otherwise, it will return false.
lt
Description: The lt function is used for numeric comparison and returns true if the subject is Less Than
its argument. If either the subject or the argument cannot be coerced into a Number,
this function returns false.
Subject Type: Number
Arguments:
-
value : The number to compare the Subject to.
Return Type: Boolean
Examples: ${fileSize:lt( 1048576 )} will return true if the size of the FlowFile’s content is less than
1 megabyte (1048576 bytes). Otherwise, it will return false.
le
Description: The le function is used for numeric comparison and returns true if the subject is Less Than
Or Equal To its argument. If either the subject or the argument cannot be coerced into a Number,
this function returns false.
Subject Type: Number
Arguments:
-
value : The number to compare the Subject to.
Return Type: Boolean
Examples: ${fileSize:le( 1048576 )} will return true if the size of the FlowFile’s content is at most
(less than or equal to) 1 megabyte (1048576 bytes). Otherwise, it will return false.
and
Description: The and function takes as a single argument a Boolean value and returns true if both the Subject
and the argument are true. If either the subject or the argument is false or cannot be coerced into a Boolean,
the function returns false. Typically, this is used with an embedded Expression as the argument.
Subject Type: Boolean
Arguments:
-
condition : The right-hand-side of the and Expression
Return Type: Boolean
Examples: We can check if the filename is both all lower-case and has at least 5 characters by using the Expression
${filename:toLower():equals( ${filename} ):and(
${filename:length():ge(5)}
)}
or
Description: The or function takes as a single argument a Boolean value and returns true if either the Subject
or the argument is true. If both the subject and the argument are false, the function returns false. If
either the Subject or the argument cannot be coerced into a Boolean value, this function will return false.
Subject Type: Boolean
Arguments:
-
condition : The right-hand-side of the and Expression
Return Type: Boolean
Examples: The following example will return true if either the filename has exactly 5 characters or if
the filename is all lower-case.
${filename:toLower():equals( ${filename} ):or(
${filename:length():equals(5)}
)}
not
Description: The not function returns the negation of the Boolean value of the subject.
Subject Type: Boolean
Arguments: No arguments
Return Type: Boolean
Examples: We can invert the value of another function by using the not function, as
${filename:equals('hello.txt'):not()}. This will return true if the filename is NOT equal to
"hello.txt" and will return false if the filename is "hello.txt."
String Manipulation
Each of the following functions manipulates a String in some way.
toUpper
Description: This function converts the Subject into an all upper-case String. Said another way, it replaces any lowercase letter with the uppercase equivalent.
Subject Type: String
Arguments: No arguments
Return Type: String
Examples: If the "filename" attribute is "abc123.txt", then the Expression ${filename:toUpper()}
will return "ABC123.TXT"
toLower
Description: This function converts the Subject into an all lower-case String. Said another way, it replaces any uppercase letter with the lowercase equivalent.
Subject Type: String
Arguments: No arguments
Return Type: String
Examples: If the "filename" attribute is "ABC123.TXT", then the Expression ${filename:toLower()}
will return "abc123.txt"
trim
Description: The trim function will remove any leading or trailing white space from its subject.
Subject Type: String
Arguments: No arguments
Return Type: String
Examples: If the attribute attr has the value " 1 2 3 ", then the Expression ${attr:trim()} will
return the value "1 2 3".
urlEncode
Description: Returns a URL-friendly version of the Subject. This is useful, for instance, when using an attribute value to indicate the URL of a website.
Subject Type: String
Arguments: No arguments
Return Type: String
Examples: We can URL-Encode an attribute named "url" by using the Expression ${url:urlEncode()}. If
the value of the "url" attribute is "https://nifi.apache.org/some value with spaces", this
Expression will then return "https://nifi.apache.org/some%20value%20with%20spaces".
urlDecode
Description: Converts a URL-friendly version of the Subject into a human-readable form.
Subject Type: String
Arguments: No arguments
Return Type: String
Examples: If we have a URL-Encoded attribute named "url" with the value
"https://nifi.apache.org/some%20value%20with%20spaces", then the Expression
${url:urlDecode()} will return "https://nifi.apache.org/some value with spaces".
substring
Description: Returns a portion of the Subject, given a starting index and an optional ending index. If the ending index is not supplied, it will return the portion of the Subject starting at the given start index and ending at the end of the Subject value.
The starting index and ending index are zero-based. That is, the first character is referenced by using
the value 0, not 1.
If either the starting index is or the ending index is not a number, this function call will result in an error.
If the starting index is larger than the ending index, this function call will result in an error.
If the starting index or the ending index is greater than the length of the Subject or has a value less than 0, this function call will result in an error.
Subject Type: String
Arguments:
-
starting index : The 0-based index of the first character to capture (inclusive)
-
ending index : The 0-based index of the last character to capture (exclusive)
Return Type: String
Examples:
If we have an attribute named "filename" with the value "a brand new filename.txt", then the following Expressions will result in the following values:
Expression |
Value |
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substringBefore
Description: Returns a portion of the Subject, starting with the first character of the Subject and ending with the character immediately before the first occurrence of the argument. If the argument is not present in the Subject, the entire Subject will be returned.
Subject Type: String
Arguments:
-
value : The String to search for in the Subject
Return Type: String
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will result in the following values:
Expression |
Value |
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substringBeforeLast
Description: Returns a portion of the Subject, starting with the first character of the Subject and ending with the character immediately before the last occurrence of the argument. If the argument is not present in the Subject, the entire Subject will be returned.
Subject Type: String
Arguments:
-
value : The String to search for in the Subject
Return Type: String
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will result in the following values:
Expression |
Value |
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substringAfter
Description: Returns a portion of the Subject, starting with the character immediately after the first occurrence of the argument and extending to the end of the Subject. If the argument is not present in the Subject, the entire Subject will be returned.
Subject Type: String
Arguments:
-
value : The String to search for in the Subject
Return Type: String
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will result in the following values:
Expression |
Value |
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substringAfterLast
Description: Returns a portion of the Subject, starting with the character immediately after the last occurrence of the argument and extending to the end of the Subject. If the argument is not present in the Subject, the entire Subject will be returned.
Subject Type: String
Arguments:
-
value : The String to search for in the Subject
Return Type: String
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will result in the following values:
Expression |
Value |
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getDelimitedField
Description: Parses the Subject as a delimited line of text and returns just a single field from that delimited text.
Subject Type: String
Arguments:
-
index : The index of the field to return. A value of 1 will return the first field, a value of 2 will return the second field, and so on.
-
delimiter : Optional argument that provides the character to use as a field separator. If not specified, a comma will be used. This value must be exactly 1 character.
-
quoteChar : Optional argument that provides the character that can be used to quote values so that the delimiter can be used within a single field. If not specified, a double-quote (") will be used. This value must be exactly 1 character.
-
escapeChar : Optional argument that provides the character that can be used to escape the Quote Character or the Delimiter within a field. If not specified, a backslash (\) is used. This value must be exactly 1 character.
-
stripChars : Optional argument that specifies whether or not quote characters and escape characters should be stripped. For example, if we have a field value "1, 2, 3" and this value is true, we will get the value
1, 2, 3, but if this value is false, we will get the value"1, 2, 3"with the quotes. The default value is false. This value must be eithertrueorfalse.
Return Type: String
Examples: If the "line" attribute contains the value "Jacobson, John", 32, Mr. and the "altLine" attribute contains the value Jacobson, John|32|Mr. then the following Expressions will result in the following values:
Expression |
Value |
|
_(space)_32 |
|
32 |
|
"Jacobson, John" |
|
Jacobson, John |
`${altLine:getDelimitedField(1, ' |
')} |
append
Description: The append function returns the result of appending the argument to the value of
the Subject. If the Subject is null, returns the argument itself.
Subject Type: String
Arguments:
-
value : The String to append to the end of the Subject
Return Type: String
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the Expression
${filename:append('.gz')} will return "a brand new filename.txt.gz".
prepend
Description: The prepend function returns the result of prepending the argument to the value of
the Subject. If the subject is null, returns the argument itself.
Subject Type: String
Arguments:
-
value : The String to prepend to the beginning of the Subject
Return Type: String
Examples: If the "filename" attribute has the value "filename.txt", then the Expression
${filename:prepend('a brand new ')} will return "a brand new filename.txt".
replace
Description: Replaces occurrences of one String within the Subject with another String.
Subject Type: String
Arguments:
-
Search String : The String to find within the Subject
-
Replacement : The value to replace Search String with
Return Type: String
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will provide the following results:
Expression |
Value |
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replaceAll
Description: The replaceAll function takes two String arguments: a Regular Expression (Data Integration Tool uses the Java Pattern
syntax), and a replacement string. The return value is the result of substituting the replacement string for
all patterns within the Subject that match the Regular Expression.
Subject Type: String
Arguments:
Arguments:
-
Regex : he Regular Expression (in Java syntax) to match in the Subject
-
Replacement : The value to use for replacing matches in the Subject. If the regular expression argument uses Capturing Groups, back references are allowed in the replacement.
Return Type: String
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will provide the following results:
Expression |
Value |
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replaceNull
Description: The replaceNull function returns the argument if the Subject is null. Otherwise,
returns the Subject.
Subject Type: Any
Arguments:
-
Replacement : The value to return if the Subject is null.
Return Type: Type of Subject if Subject is not null; else, type of Argument
Examples: If the attribute "filename" has the value "a brand new filename.txt" and the attribute
"hello" does not exist, then the Expression ${filename:replaceNull('abc')} will return
"a brand new filename.txt", while ${hello:replaceNull('abc')} will return "abc".
replaceEmpty
Description: The replaceEmpty function returns the argument if the Subject is null or
if the Subject consists only of white space (new line, carriage return, tab, space). Otherwise,
returns the Subject.
Subject Type: String
Arguments:
-
Replacement : The value to return if the Subject is null or empty.
Return Type: String
Examples: If the attribute "filename" has the value "a brand new filename.txt" and the attribute
"hello" has the value " ", then the Expression ${filename:replaceEmpty('abc')} will return
"a brand new filename.txt", while ${hello:replaceEmpty('abc')} will return "abc".
length
Description: Returns the length of the Subject
Subject Type: String
Arguments: No arguments
Return Type: Number
Examples: If the attribute "filename" has a value of "a brand new filename.txt" and the attribute
"hello" does not exist, then the Expression ${filename:length()} will return 24. ${hello:length()}
will return 0.
Searching
Each of the following functions is used to search its subject for some value.
startsWith
Description: Returns true if the Subject starts with the String provided as the argument,
false otherwise.
Subject Type: String
Arguments:
-
value : The value to search for
Return Type: Boolean
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the Expression
${filename:startsWith('a brand')} will return true. ${filename:startsWith('A BRAND')} will
return false. ${filename:toUpper():startsWith('A BRAND')} returns true.
endsWith
Description: Returns true if the Subject ends with the String provided as the argument,
false otherwise.
Subject Type: String
Arguments:
-
value : The value to search for
Return Type: Boolean
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the Expression
${filename:endsWith('txt')} will return true. ${filename:endsWith('TXT')} will
return false. ${filename:toUpper():endsWith('TXT')} returns true.
contains
Description: Returns true if the Subject contains the value of the argument anywhere in the value.
Subject Type: String
Arguments:
-
value : The value to search for
Return Type: Boolean
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the Expression
${filename:contains('new')} will return true. ${filename:contains('NEW')} will
return false. ${filename:toUpper():contains('NEW')} returns true.
find
Description: Returns true if the Subject contains any sequence of characters that matches the
Regular Expression provided by the argument.
Subject Type: String
Arguments:
-
Regex : The Regular Expression (in the Java Pattern syntax) to match against the Subject
Return Type: Boolean
Examples:
If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will provide the following results:
Expression |
Value |
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matches
Description: Returns true if the Subject exactly matches the Regular Expression provided by the argument.
Subject Type: String
Arguments:
-
Regex : The Regular Expression (in the Java Pattern syntax) to match against the Subject
Return Type: Boolean
Examples:
If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will provide the following results:
Expression |
Value |
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indexOf
Description: Returns the index of the first character in the Subject that matches the String value provided
as an argument. If the argument is found multiple times within the Subject, the value returned is the
starting index of the first occurrence.
If the argument cannot be found in the Subject, returns -1. The index is zero-based. This means that if
the search string is found at the beginning of the Subject, the value returned will be 0, not 1.
Subject Type: String
Arguments:
-
value : The value to search for in the Subject
Return Type: Number
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will provide the following results:
Expression |
Value |
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lastIndexOf
Description: Returns the index of the first character in the Subject that matches the String value provided
as an argument. If the argument is found multiple times within the Subject, the value returned is the
starting index of the last occurrence.
If the argument cannot be found in the Subject, returns -1. The index is zero-based. This means that if
the search string is found at the beginning of the Subject, the value returned will be 0, not 1.
Subject Type: String
Arguments:
-
value : The value to search for in the Subject
Return Type: Number
Examples: If the "filename" attribute has the value "a brand new filename.txt", then the following Expressions will provide the following results:
Expression |
Value |
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Mathematical Operations and Numeric Manipulation
plus
Description: Adds a numeric value to the Subject. If either the argument or the Subject cannot be
coerced into a Number, returns null.
Subject Type: Number
Arguments:
-
Operand : The value to add to the Subject
Return Type: Number
Examples: If the "fileSize" attribute has a value of 100, then the Expression ${fileSize:plus(1000)}
will return the value 1100.
minus
Description: Subtracts a numeric value from the Subject.
Subject Type: Number
Arguments:
-
Operand : The value to subtract from the Subject
Return Type: Number
Examples: If the "fileSize" attribute has a value of 100, then the Expression ${fileSize:minus(100)}
will return the value 0.
multiply
Description: Multiplies a numeric value by the Subject and returns the product.
Subject Type: Number
Arguments:
-
Operand : The value to multiple the Subject by
Return Type: Number
Examples: If the "fileSize" attribute has a value of 100, then the Expression ${fileSize:multiply(1024)}
will return the value 102400.
divide
Description: Divides a numeric value by the Subject and returns the result, rounded down to the nearest integer.
Subject Type: Number
Arguments:
-
Operand : The value to add divide the Subject by
Return Type: Number
Examples: If the "fileSize" attribute has a value of 100, then the Expression ${fileSize:divide(12)}
will return the value 8.
mod
Description: Performs a modular division of the Subject by the argument. That is, this function will divide the Subject by the value of the argument and return not the quotient but rather the remainder.
Subject Type: Number
Arguments:
-
Operand : The value to divide the Subject by
Return Type: Number
Examples: If the "fileSize" attribute has a value of 100, then the Expression ${fileSize:mod(12)}
will return the value 4.
toRadix
Description: Converts the Subject from a Base 10 number to a different Radix (or number base). An optional second argument can be used to indicate the minimum number of characters to be used. If the converted value has fewer than this number of characters, the number will be padded with leading zeroes.
Subject Type: Number
Arguments:
-
Desired Base : A Number between 2 and 36 (inclusive)
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Padding : Optional argument that specifies the minimum number of characters in the converted output
Return Type: String
Examples: If the "fileSize" attributes has a value of 1024, then the following Expressions will yield the following results:
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Value |
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Date Manipulation
format
Description: Formats a number as a date/time according to the format specified by the argument. The argument must be a String that is a valid Java SimpleDateFormat format. The Subject is expected to be a Number that represents the number of milliseconds since Midnight GMT on January 1, 1970.
Subject Type: Number
Arguments:
-
format : The format to use in the Java SimpleDateFormat syntax
Return Type: String
Examples: If the attribute "time" has the value "1420058163264", then the following Expressions will yield the following results:
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Value |
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toDate
Description: Converts a String into a Date data type, based on the format specified by the argument. The argument must be a String that is a valid Java SimpleDateFormat syntax. The Subject is expected to be a String that is formatted according the argument.
Subject Type: String
Arguments:
-
format : The current format to use when parsing the Subject, in the Java SimpleDateFormat syntax.
Return Type: Date
Examples: If the attribute "year" has the value "2014" and the attribute "time" has the value "2014/12/31 15:36:03.264Z",
then the Expression ${year:toDate('yyyy')} will return a Date data type with a value representing Midnight GMT on
January 1, 2014. The Expression ${time:toDate("yyyy/MM/dd HH:mm:ss.SSS'Z'")} will result in a Date data type for
15:36:03.264 GMT on December 31, 2014.
Often, this function is used in conjunction with the format function to change the format of a date/time. For example,
if the attribute "date" has the value "12-24-2014" and we want to change the format to "2014/12/24", we can do so by
chaining together the two functions: ${date:toDate('MM-dd-yyyy'):format('yyyy/MM/dd')}.
now
Description: Returns the current date and time as a Date data type object.
Subject Type: No Subject
Arguments: No arguments
Return Type: Date
Examples: We can get the current date and time as a Date data type by using the now function: ${now()}. As an example,
on Wednesday December 31st 2014 at 36 minutes after 3pm and 36.123 seconds EST ${now()} would be evaluated to be a
Date type representing that time. Since whole Expression Language expressions can only return Strings it would formatted as
Wed Dec 31 15:36:03 EST 2014 when the expression completes.
Utilizing the toNumber method, now can provide the current date and time as the number of milliseconds since
Midnight GMT on January 1, 1970. For instance, if instead of executing ${now()} in the previous example ${now():toNumber()}
was run then it would output 1453843201123. This method provides millisecond-level precision and provides the ability to
manipulate the value.
Expression |
Value |
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A Date type representing the current date and time to the nearest millisecond |
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The number of milliseconds since midnight GMT Jan 1, 1970 ( |
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A number presenting the time 24 hours ago |
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The current year |
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The day of the week that was yesterday,
as a 3-letter abbreviation (For example, |
Type Coercion
Subjectless Functions
While the majority of functions in the Expression Language are called by using the syntax
${attributeName:function()}, there exist a few functions that are not expected to have subjects.
In this case, the attribute name is not present. For example, the IP address of the machine can
be obtained by using the Expression ${ip()}. All of the functions in this section are to be called
without a subject. Attempting to call a subjectless function and provide it a subject will result in
an error when validating the function.
ip
Description: Returns the IP address of the machine.
Subject Type: No subject
Arguments: No arguments
Return Type: String
Examples: The IP address of the machine can be obtained by using the Expression ${ip()}.
hostname
Description: Returns the Hostname of the machine. An optional argument of type Boolean can be provided
to specify whether or not the Fully Qualified Domain Name should be used. If false, or not specified,
the hostname will not be fully qualified. If the argument is true but the fully qualified hostname
cannot be resolved, the simple hostname will be returned.
Subject Type: No subject
Arguments:
-
Fully Qualified : Optional parameter that specifies whether or not the hostname should be fully qualified. If not specified, defaults to false.
Return Type: String
Examples: The fully qualified hostname of the machine can be obtained by using the Expression ${hostname(true)},
while the simple hostname can be obtained by using either ${hostname(false)} or simply ${hostname()}.
UUID
Description: Returns a randomly generated UUID.
Subject Type: No Subject
Arguments: No arguments
Return Type: String
Examples: ${UUID()} returns a value similar to de305d54-75b4-431b-adb2-eb6b9e546013
nextInt
Description: Returns a one-up value (starting at 0) and increasing over the lifetime of the running instance of Data Integration Tool. This value is not persisted across restarts and is not guaranteed to be unique across a cluster. This value is considered "one-up" in that if called multiple times across the Data Integration Tool instance, the values will be sequential. However, this counter is shared across all Data Integration Tool components, so calling this function multiple times from one Processor will not guarantee sequential values within the context of a particular Processor.
Subject Type: No Subject
Arguments: No arguments
Return Type: Number
Examples: If the previous value returned by nextInt was 5, the Expression ${nextInt():divide(2)} obtains the next available
integer (6) and divides the result by 2, returning a value of 3.
literal
Description: Returns its argument as a literal String value. This is useful in order to treat a string or a number at the beginning of an Expression as an actual value, rather than treating it as an attribute name. Additionally, it can be used when the argument is an embedded Expression that we would then like to evaluate additional functions against.
Subject Type: No Subject
Arguments:
-
value : The value to be treated as a literal string, number, or boolean value.
Return Type: String
Examples: ${literal(2):gt(1)} returns true
${literal( ${allMatchingAttributes('a.*'):count()} ):gt(3)} returns true if there are more than 3 attributes whose
names begin with the letter a.
Evaluating Multiple Attributes
When it becomes necessary to evaluate the same conditions against multiple attributes, this can be accomplished by means of the
and and or functions. However, this quickly becomes tedious, error-prone, and difficult to maintain. For this reason, Data Integration Tool
provides several functions for evaluating the same conditions against groups of attributes at the same time.
anyAttribute
Description: Checks to see if any of the given attributes, match the given condition. This function has no subject and takes one or more
arguments that are the names of attributes to which the remainder of the Expression is to be applied. If any of the attributes specified,
when evaluated against the rest of the Expression, returns a value of true, then this function will return true. Otherwise, this function
will return false.
Subject Type: No Subject
Arguments:
-
Attribute Names : One or more attribute names to evaluate
Return Type: Boolean
Examples: Given that the "abc" attribute contains the value "hello world", "xyz" contains "good bye world", and "filename" contains "file.txt" consider the following examples:
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allAttributes
Description: Checks to see if any of the given attributes, match the given condition. This function has no subject and takes one or more
arguments that are the names of attributes to which the remainder of the Expression is to be applied. If all of the attributes specified,
when evaluated against the rest of the Expression, returns a value of true, then this function will return true. Otherwise, this function
will return false.
Subject Type: No Subject
Arguments:
-
Attribute Names : One or more attribute names to evaluate
Return Type: Boolean
Examples: Given that the "abc" attribute contains the value "hello world", "xyz" contains "good bye world", and "filename" contains "file.txt" consider the following examples:
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anyMatchingAttribute
Description: Checks to see if any of the given attributes, match the given condition. This function has no subject and takes one or more
arguments that are Regular Expressions to match against attribute names. Any attribute whose name matches one of the supplied
Regular Expressions will be evaluated against the rest of the Expression. If any of the attributes specified,
when evaluated against the rest of the Expression, returns a value of true, then this function will return true. Otherwise, this function
will return false.
Subject Type: No Subject
Arguments:
-
Regex : One or more Regular Expressions (in the Java Pattern syntax) to evaluate against attribute names
Return Type: Boolean
Examples: Given that the "abc" attribute contains the value "hello world", "xyz" contains "good bye world", and "filename" contains "file.txt" consider the following examples:
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Value |
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allMatchingAttributes
Description: Checks to see if any of the given attributes, match the given condition. This function has no subject and takes one or more
arguments that are Regular Expressions to match against attribute names. Any attribute whose name matches one of the supplied
Regular Expressions will be evaluated against the rest of the Expression. If all of the attributes specified,
when evaluated against the rest of the Expression, return a value of true, then this function will return true. Otherwise, this function
will return false.
Subject Type: No Subject
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Regex : One or more Regular Expressions (in the Java Pattern syntax) to evaluate against attribute names
Return Type: Boolean
Examples: Given that the "abc" attribute contains the value "hello world", "xyz" contains "good bye world", and "filename" contains "file.txt" consider the following examples:
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Value |
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anyDelineatedValue
Description: Splits a String apart according to a delimiter that is provided, and then evaluates each of the values against
the rest of the Expression. If the Expression, when evaluated against any of the individual values, returns true, this
function returns true. Otherwise, the function returns false.
Subject Type: No Subject
Arguments:
-
Delineated Value : The value that is delineated. This is generally an embedded Expression, though it does not have to be.
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Delimiter : The value to use to split apart the delineatedValue argument.
Return Type: Boolean
Examples: Given that the "number_list" attribute contains the value "1,2,3,4,5", and the "word_list" attribute contains the value "the,and,or,not", consider the following examples:
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Value |
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allDelineatedValues
Description: Splits a String apart according to a delimiter that is provided, and then evaluates each of the values against
the rest of the Expression. If the Expression, when evaluated against all of the individual values, returns true in each
case, then this function returns true. Otherwise, the function returns false.
Subject Type: No Subject
Arguments:
-
Delineated Value : The value that is delineated. This is generally an embedded Expression, though it does not have to be.
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Delimiter : The value to use to split apart the delineatedValue argument.
Return Type: Boolean
Examples: Given that the "number_list" attribute contains the value "1,2,3,4,5", and the "word_list" attribute contains the value "those,known,or,not", consider the following examples:
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join
Description: Aggregate function that concatenates multiple values with the specified delimiter. This function
may be used only in conjunction with the allAttributes, allMatchingAttributes, and allDelineatedValues
functions.
Subject Type: String
Arguments:
-
Delimiter : The String delimiter to use when joining values
Return Type: String
Examples: Given that the "abc" attribute contains the value "hello world", "xyz" contains "good bye world", and "filename" contains "file.txt" consider the following examples:
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count
Description: Aggregate function that counts the number of non-null, non-false values returned by the
allAttributes, allMatchingAttributes, and allDelineatedValues. This function
may be used only in conjunction with the allAttributes, allMatchingAttributes, and allDelineatedValues
functions.
Subject Type: Any
Arguments: No arguments
Return Type: Number
Examples: Given that the "abc" attribute contains the value "hello world", "xyz" contains "good bye world", and "number_list" contains "1,2,3,4,5" consider the following examples:
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