StructuredDataWriter

Home \| Table of Contents	StructuredDataWriter	CloverETL 4.6.1
Prev	Writers	Next

Short Description

StructuredDataWriter writes data to files (local or remote, delimited, fixed-length, or mixed) with user-defined structure. It can also compress output files and write to output port, or dictionary.

Component	Data output	Input ports	Output ports	Transformation	Transf. required	Java	CTL	Auto-propagated metadata
StructuredDataWriter	structured flat file	1-3	0-1

Icon

Ports

Port type	Number	Description	Metadata
Input	0	Records for body	Any
	1	Records for header	Any
	2	Records for footer	Any
Output	0	For port writing. See Writing to Output Port.	One field (`byte`, `cbyte`, `string`).

Metadata

StructuredDataWriter does not propagate metadata.

StructuredDataWriter has no metadata templates.

Metadata on output port has one field (byte, cbyte or string).

StructuredDataWriter Attributes

Attribute	Req	Description	Possible values
Basic
File URL	yes	Attribute specifying where received data will be written (flat file, output port, dictionary). See Supported File URL Formats for Writers.
Charset		Encoding of records written to the output.	UTF-8 (default) \| <other encodings>
Append		By default, new records overwrite the older ones. If set to `true`, new records are appended to the older records stored in the output file(s).	false (default) \| true
Body mask		Mask used to write the body of the output file(s). It can be based on the records received through the first input port. See Masks and Output File Structure for more information about definition of Body mask and resulting output structure.	Default Body Structure (default) \| user-defined
Header mask	^[1]	Mask used to write the header of the output file(s). It can be based on the records received through the second input port. See Masks and Output File Structure for more information about definition of Header mask and resulting output structure.	empty (default) \| user-defined
Footer mask	^[2]	Mask used to write the footer of the output file(s). It can be based on the records received through the third input port. See Masks and Output File Structure for more information about definition of Footer mask and resulting output structure.	empty (default) \| user-defined
Advanced
Create directories		By default, non-existing directories are not created. If set to `true`, they are created.	false (default) \| true
Records per file		Maximum number of records to be written to one output file.	1-N
Bytes per file		Maximum size of one output file in bytes.	1-N
Number of skipped records		Number of records to be skipped. See Selecting Output Records.	0-N
Max number of records		Maximum number of records to be written to all output files. See Selecting Output Records.	0-N
Partition key		Key whose values define the distribution of records among multiple output files. See Partitioning Output into Different Output Files for more information.
Partition lookup table	^[1]	ID of lookup table serving for selecting records that should be written to output file(s). See Partitioning Output into Different Output Files for more information.
Partition file tag		By default, output files are numbered. If it is set to `Key file tag`, output files are named according to the values of Partition key or Partition output fields. See Partitioning Output into Different Output Files for more information.	Number file tag (default) \| Key file tag
Partition output fields	^[1]	Fields of Partition lookup table whose values serve to name output file(s). See Partitioning Output into Different Output Files for more information.
Partition unassigned file name		Name of the file into which the unassigned records should be written if there are any. If not specified, data records whose key values are not contained in Partition lookup table are discarded. See Partitioning Output into Different Output Files for more information.
Sorted input		In case of partitioning into multiple output files is turned on, all output files are open at once. Which could lead to undesirable memory footprint for many output files (thousands). Moreover, for example unix-based OS usually have very strict limitation of number of simultaneously open files (1024) per process. In case you run into one of these limitations, consider to sort the data according partition key using one of our standard sorting components and set this attribute to true. The partitioning algorithm does not need to keep open all output files, just the last one is open at one time. See Partitioning Output into Different Output Files for more information.	false (default) \| true
Create empty files		If set to `false`, prevents the component from creating empty output file when there are no input records.	true (default) \| false
^[1] Must be specified if second input port is connected. However, does not need to be based on input data records. ^[2] Must be specified if third input port is connected. However, does not need to be based on input data records.

Details

Masks and Output File Structure

Output File Structure

Output file consists of header, body, and footer, in this order.
Each of them is defined by specifying corresponding mask.
Having defined the mask, the mask content is written repeatedly, one mask is written for each incoming record.
If the Records per file attribute is defined, the output structure is distributed among various output files, but this attribute applies for Body mask only. Header and footer are the same for all output files.

Defining a Mask

Body mask, Header mask, and Footer mask can be defined in the Mask dialog. This dialog opens after clicking corresponding attribute row. In its window, you can see the Metadata and Mask panes.

You can define the mask either without field values or with field values.

Field values are referred using field names preceded by dollar sign.

Figure 49.26. Create Mask Dialog

You do not have to map all input metadata fields.

Output can contain additional text not coming from input metadata. E.g. Return address on figure above.

You can use StructuredDataWriter to generate XML files or to fill in the template.

Default Masks

Default Header mask is empty. But it must be defined if second input port is connected.
Default Footer mask is empty. But it must be defined if third input port is connected.
Default Body mask is empty. However, the resulting default body structure looks like the following:
```
<recordName>
	<field1name>field1value</field1name>
	<field2name>field2value</field2name>
	...
	<fieldNname>fieldNvalue</fieldNname>
</recordName>
```
This structure is written to the output file(s) for all records.
If Records per file is set, only the specified number of records are used for body in each output file at most.

Notes and Limitatinos

StructuredDataWriter cannot write lists and maps.

Examples

Writing Page with Header and Footer

Legacy application requires data in the following file structure: header, up to five data records and blank line. Convert data to format accepted by the legacy application:

F0512#4d6f6465726e20616e642070756e6368206361726420636f6d70617469626c65
Francis   Smith     77        
Jonathan  Brown     5         
Kate      Wood      75        
John      Black     3         
Elisabeth Doe       87

Solution

Connect an edge providing particular records to the first input port of StructuredDataWriter (metadata field body) and edge providing header to the second input port (metadata field header).

Edit the attributes:

Attribute	Value
File URL	${DATOUT_DIR}/file_$$.txt
Body mask	$body
Header mask	$header
Footer mask
Records per file	5

Adjust line break in Body mask, Header mask and Footer mask attributes according to the input records. If input records have line break, do not add line break after the string $body and $header. If input records do not have line break, add line break after $body and $header; fill in the line break to the attribute Footer mask too.

Best Practices

To write record with fixed-length metadata use FlatFileWriter to convert several fixed-length metadata fields into one field. Subsequently write the output from FlatFileWriter using StructuredDataWriter.

We recommend users to explicitly specify Charset.

Troubleshooting

If you partition data unsorted data into many output files, you may reach the limit of simultaneously opened files. This can you avoid by sorting the input and using attribute sorted input.

Prev	Up	Next
SpreadsheetDataWriter	Home \| Table of Contents	TableauWriter