FileAttributesFilter

Retrieves and exposes a record from a delimiter-separated file. Lookup of the record is performed using a specified key, whose value is derived from an expression. The resulting record is exposed in an object whose location is specified by the target expression. If a matching record cannot be found, then the resulting object is empty.

The retrieval of the record is performed lazily; it does not occur until the first attempt to access a value in the target. This defers the overhead of file operations and text processing until a value is first required. This also means that the value expression is not evaluated until the object is first accessed.

Usage

{
     "name": string,
     "type": "FileAttributesFilter",
     "config": {
         "file": expression,
         "charset": string,
         "separator": string,
         "header": boolean,
         "fields": [ string, ... ],
         "target": lvalue-expression,
         "key": string,
         "value": runtime expression<string>
     }
}

Properties

"file": expression, required

The file containing the record to be read.

See also Expressions.

"charset": string, optional

The character set in which the file is encoded.

Default: "UTF-8".

"separator": separator identifier string, optional

The separator character, which is one of the following:

COLON

Unix-style colon-separated values, with backslash as the escape character.

COMMA

Comma-separated values, with support for quoted literal strings.

TAB

Tab separated values, with support for quoted literal strings.

Default: COMMA

"header": boolean, optional

The setting to treat or not treat the first row of the file as a header row.

When the first row of the file is treated as a header row, the data in that row is disregarded and cannot be returned by a lookup operation.

Default: true.

"fields": array of strings, optional

A list of keys in the order they appear in a record.

If fields is not set, the keys are assigned automatically by the column numbers of the file.

"target": lvalue-expression, required

Expression that yields the target object to contain the record.

The target object is a Map<String, String>, where the fields are the keys. For example, if the target is ${attributes.file} and the record has a username field and a password field mentioned in the fields list, Then you can access the user name as ${attributes.file.username} and the password as ${attributes.file.password}.

See also Expressions.

"key": string, required

The key used for the lookup operation.

"value": runtime expression<string>, required

The value to be looked-up in the file.

See also Expressions.