JDD: Driver Locale | Handles | Data Sources | Data Driver | Error Messages | API: Connect Read Update Create Bulk Insert
JDD is only an abstract interface specification, concrete implementation is provided by various drivers written in J. Since it is written in J with C API calls, most likely both Linux and Windows are supported.
Currently, drivers for SQLite and MySQL have been implemented.
Each driver is contained in its own class definition, so that its class definition has to be loaded first,
NB. file for each JDD driver will be placed under the folder ~addons/data load 'data/ddmysql'
this will load a class 'jddmysql', verbs can be accessed with fully qualified names such as ddcon_jddmysql_. However some initialization is required before use and it it more convenient to create an object (numbered locale) from it.
NB. note the dyad conew will call the verb 'create' to do initialization. db=. '' conew 'jddmysql'
Subsequently, verbs inside locale db will be used.
ch=. ddcon__db '......' a lot of codes here dddis__db ch
Finally, remember to cleanup locale
This is the recommended way to use JDD in writing new codes.
In order to make migration from J/ODBC easier, verbs in JDD can also be exported to z locale with the verb setzlocale
The general pattern looks like this,
load 'data/ddmysql' setzlocale_jddmysql_ '' ch=. ddcon '......' a lot of codes here dddis ch
While this method have advantages such as,
- can run un-modified codes written for J/ODBC
- less typing in an interactive session
- conflicts with J/ODBC
- different JDD drivers can not be used simultaneously