JML: OpenJUMP JML format

Driver short name


Build dependencies

(read support needs libexpat)

OGR has support for reading and writing .JML files used by the OpenJUMP software. Read support is only available if GDAL is built with expat library support

.jml is a variant of GML format. There is no formal definition of the format. It supports a single layer per file, mixed geometry types, and for each feature, a geometry and several attributes of type integer, double, string, date or object. That object data type, used for example to store 64 bit integers, but potentially arbitrary serialized Java objects, is converted as string when reading. Contrary to GML, the definition of fields is embedded in the .jml file, at its beginning.

Support for reading and writing spatial reference systems requires GDAL 2.3 or later.

Driver capabilities

Supports Create()

This driver supports the GDALDriver::Create() operation

Supports Georeferencing

This driver supports georeferencing

Supports VirtualIO

This driver supports virtual I/O operations (/vsimem/, etc.)

Encoding issues

Expat library supports reading the following built-in encodings :


  • UTF-8

  • UTF-16

  • ISO-8859-1

  • Windows-1252

The content returned by OGR will be encoded in UTF-8, after the conversion from the encoding mentioned in the file header is. But files produced by OpenJUMP are always UTF-8 encoded.

When writing a JML file, the driver expects UTF-8 content to be passed in.


OpenJUMP uses an optional string attribute called "R_G_B" to determine the color of objects. The field value is "RRGGBB" where RR, GG, BB are respectively the value of the red, green and blue components expressed as hexadecimal values from 00 to FF. When reading a .jml file, OGR will translate the R_G_B attribute to the Feature Style encoding, unless a OGR_STYLE attribute is present. When writing a .jml file, OGR will extract from the Feature Style string the color of the PEN tool or the forecolor of the BRUSH tool to write the R_G_B attribute, unless the R_G_B attribute is defined in the provided feature. The addition of the R_G_B attribute can be disabled by setting the CREATE_R_G_B_FIELD layer creation option to NO.

Creation Issues

The JML writer supports the following layer creation options:

  • CREATE_R_G_B_FIELD=[YES/NO]: Defaults to YES. whether the create a R_G_B field that will contain the color of the PEN tool or the forecolor of the BRUSH tool of the OGR Feature Style string.

  • CREATE_OGR_STYLE_FIELD=[YES/NO]: Defaults to NO. whether the create a OGR_STYLE field that will contain the Feature Style string.

See Also


The author wishes to thank Jukka Rahkonen for funding the development of this driver.