FlatFileReader

Short Description

FlatFileReader reads data from flat files, such as CSV (comma-separated values) file and delimited, fixed-length, or mixed text files. The component can read a single file as well as a collection of files placed on a local disk or remotely. Remote files are accessible via HTTP, HTTPS, FTP, or SFTP protocols. Using this component, ZIP and TAR archives of flat files can be read. Also reading data from an input port, or dictionary is supported. FlatFileReader has an alias - UniversalDataReader.

COMPONENT

DATA SOURCE

INPUT PORTS

OUTPUT PORTS

EACH TO ALL INPUTS

DIFFERENT TO DIFFERENT OUTPUTS

TRANSFORMATION

TRANSF. REQ.

JAVA

CTL

AUTO-PROPAGATED METADATA

FlatFileReader

flat file

0-1

1-2

✓

Ports

PORT TYPE

NUMBER

REQUIRED

DESCRIPTION

METADATA

Input

For Input Port Reading.

include specific byte/ cbyte/ string field

Output

✓

For correct data records

Any

For incorrect data records

specific structure, see table below

Metadata

FlatFileReader does not propagate metadata. This component has metadata templates available. The optional logging port for incorrect records has to define the following metadata structure - the record contains exactly five fields (named arbitrarily) of given types in the following order:

FIELD NUMBER

FIELD NAME

DATA TYPE

DESCRIPTION

recordNo

long

The position of an erroneous record in the dataset (record numbering starts at 1).

fieldNo

integer

The position of an erroneous field in the record (1 stands for the first field, i.e. that of index 0).

originalData

string | byte | cbyte

An erroneous record in raw form (including all field and record delimiters).

errorMessage

string | byte | cbyte

A source file in which the error occurred.

fileURL

string

A source file in which the error occurred.

Metadata on output port 0 can use Autofilling Functions. The source_timestamp and source_size functions work only when reading from a file directly (if the file is an archive or it is stored at a remote location, timestamp will be empty and size will be 0).

FlatFileReader Attributes

ATTRIBUTE

REQ.

DESCRIPTION

POSSIBLE VALUES

Basic

File URL

✓

A path to a data source (flat file, input port, dictionary) to be read, see Supported File URL Formats for Readers.

Charset

Character encoding of input records (character encoding does not apply to byte fields, if the record type is fixed). The default encoding depends on DEFAULT_CHARSET_DECODER in defaultProperties.

UTF-8 |

Data policy

Specifies handling of misformatted or incorrect data, see Data Policy.

strict (default) | controlled | lenient

Trim strings

Specifies whether a leading and trailing whitespace should be removed from strings before setting them to data fields, see Trimming Data below.

default | true | false

Quoted strings

Fields containing a special character (comma, newline or double quote) have to be enclosed in quotes. Only a single/double quote is accepted as the quote character. If true, special characters are removed when read by the component (they are not treated as delimiters). Example: To read input data "25"|"John", switch Quoted strings to true and set Quote character to ". This will produce two fields: 25|John. By default, the value of this attribute is inherited from metadata on output port 0. See also Record Details.

false | true

Quote character

Specifies which kind of quotes will be permitted in Quoted strings. By default, the value of this attribute is inherited from metadata on output port 0. See also Record Details.

both | " | '

Advanced

Skip leading blanks

Specifies whether to skip a leading whitespace (e.g. blanks) before setting input strings to data fields. If not explicitly set (i.e. having the default value), the value of the Trim strings attribute is used. See Trimming Data below.

default | true | false

Skip trailing blanks

Specifies whether to skip a trailing whitespace (e.g. blanks) before setting input strings to data fields. If not explicitly set (i.e. having the default value), the value of the Trim strings attribute is used. See Trimming Data below.

default | true | false

Number of skipped records

The number of records/rows to be skipped from the source file(s). See Selecting Input Records.

0 (default) - N

Max number of records

The number of records to be read from the source file(s) in turn; all records are read by default. See Selecting Input Records.

1 - N

Number of skipped records per source

The number of records/rows to be skipped from each source file. By default, the value of the Skip source rows record property in output port 0 metadata is used. In case the value in metadata differs from the value of this attribute, the Number of skipped records per source value is applied, having a higher priority. See Selecting Input Records.

0 (default)- N

Max number of records per source

The number of records/rows to be read from each source file; all records from each file are read by default. See Selecting Input Records.

1 - N

Missing column handling

Specifies handling of records with fewer fields (columns) than required by metadata. If set to Treat as error, record is considered to be invalid, and the Data Policy setting is applied. If set to Fill with null, record is accepted, and missing fields are set to null, or to the default value if specified.

Treat as error (default) | Fill with null

Max error count

The maximum number of tolerated error records in input file(s); applicable only if Controlled Data Policy is set.

0 (default) - N

Treat multiple delimiters as one

If a field is delimited by a multiplied delimiter character, it will be interpreted as a single delimiter when setting to true.

false (default) | true

Incremental file

[1]

The name of a file storing the incremental key, including path. See Incremental Reading.

Incremental key

[1]

The variable storing a position of the last read record. See Incremental Reading.

Verbose

By default, a less comprehensive error notification is provided and the performance is slightly higher; however, if switched to true, more detailed information with less performance is provided.

false (default) | true

Parser

By default, the most appropriate parser is applied. Besides, the parser for processing data may be set explicitly. If an improper one is set, an exception is thrown and the graph fails. See Data Parsers below.

auto (default) |

[1] Either both or neither of these attributes must be specified.

Details

Parsed data records are sent to the first output port. The component has an optional output logging port for getting detailed information about incorrect records. Only if Data Policy is set to controlled and a proper Writer (Trash or FlatFileWriter) is connected to port 1, all incorrect records together with the information about the incorrect value, its location and the error message are sent out through this error port.

Trimming Data

Input strings are implicitly (i.e. the Trim strings attribute kept at the default value) processed before converting to a value according to the field data type as follows:
- Whitespace is removed from both the start and the end in the case of boolean, date, decimal, integer, long, or number.
- Input string is set to a field including a leading and trailing whitespace in the case of byte, cbyte, or string.
If the Trim strings attribute is set to true, all leading and trailing whitespace characters are removed. A field composed of only whitespaces is transformed to null (zero length string). The false value implies preserving all leading and trailing whitespace characters. Remember that input string representing a numerical data type or boolean can not be parsed including whitespace. Thus, use the false value carefully.
Both the Skip leading blanks and Skip trailing blanks attributes have a higher priority than Trim strings. So, the input strings trimming will be determined by the true or false values of these attributes, regardless the Trim strings value.

Data Parsers

org.jetel.data.parser.SimpleDataParser - is a very simple but fast parser with limited validation, error handling and functionality. The following attributes are not supported:
- Trim strings
- Skip leading blanks
- Skip trailing blanks
- Incremental reading
- Number of skipped records
- Max number of records
- Quoted strings
- Missing column handling
- Treat multiple delimiters as one
- Skip rows
- Verbose

On top of that, you cannot use metadata containing at least one field with one of these attributes:

the field is fixed-length
the field has no delimiter or, on the other hand, more of them
Shift is not null (see Details Pane)
Autofilling set to true
the field is byte-based

org.jetel.data.parser.DataParser - an all-round parser working with any reader settings
org.jetel.data.parser.CharByteDataParser - can be used whenever metadata contain byte-based fields mixed with char-based ones. A byte-based field is a field of one of these types: byte, cbyte or any other field whose format property starts with the "BINARY:" prefix. See Numeric Format > Binary Formats.
org.jetel.data.parser.FixLenByteDataParser - used for metadata with byte-based fields only. It parses sequences of records consisting of a fixed number of bytes.

Note: Choosing org.jetel.data.parser.SimpleDataParser while using Quoted strings will cause the Quoted strings attribute to be ignored.

Tips & Tricks

Handling records with large data fields: FlatFileReader can process input strings of even hundreds or thousands of characters when you adjust the field and record buffer sizes. Just increase the following properties according to your needs: Record.MAX_RECORD_SIZE for record serialization, DataParser.FIELD_BUFFER_LENGTH for parsing and DataFormatter.FIELD_BUFFER_LENGTH for formatting. Finally, don’t forget to increase the DEFAULT_INTERNAL_IO_BUFFER_SIZE variable to be at least 2* MAX_RECORD_SIZE. For information on how to change these property variables, see Engine Configuration.

Examples

Processing files with headers

If the first rows of your input file do not represent real data but field labels instead, set the Number of skipped records attribute. If a collection of input files with headers is read, set the Number of skipped records per source.

Handling typist’s error when creating the input file manually

If you wish to ignore accidental errors in delimiters (such as two semicolons instead of a single one as defined in metadata when the input file is typed manually), set the Treat multiple delimiters as one attribute to true. All redundant delimiter characters will be replaced by the proper one.

Incremental reading

Incremental Reading allows you to read only new records from a file. This can be done by setting the Incremental key and Incremental file attributes.

Let us have a list of customers in a file customers.dat. Each record in the file consists of a date, first name and last name:

Read the file, then add a new record and run the graph again reading only the new record.

Solution In the output metadata, create the date, firstName and lastName fields. Set their data types to date, string and string, respectively. Use the Incremental key and Incremental file attributes.

Note: If the first row of the input file is not a header, remember to set the Number of skipped records attribute to 0.

ATTRIBUTE

VALUE

Incremental key

date

Incremental file

${DATATMP_DIR}/customers_inc_key

After the first read, the output file contains five records.

Now, add a new record to the file, for example: 2018-03-01 00:51:31|Nathalie|Mangram and run the graph again.

This time, only the new record is written to the output file, ignoring the previously processed records.

Best Practices

We recommend users to explicitly specify encoding of the input file (with the Charset attribute). It ensures better portability of the graph across systems with different default encoding. The recommended encoding is UTF-8.

Troubleshooting

With default charset (UTF-8), FlatFileReader cannot parse csv files with binary data. To parse csv files with binary data, change Charset attribute.