Cayenne User Documentation
Custom DbAdapter

## How do I write an adapter to support a database that is not yet supported?

You need to implement a custom DbAdapter. Most likely you won't have to do it from scratch and can extend a JdbcAdapter or one of the existing db-specific adapters.

### If the adapter is for a database that we currently do not support and you are planning to donate it to Cayenne, you can do this first:

- Open a JIRA issue where all contributed code will go.
- Subscribe to the developer mailing list and introduce yourself to Cayenne developers.

##### Implementation procedure is roughly the following:

- Check out the latest Cayenne source from SVN. If you use Eclipse, follow these instructions to setup the projects.

- Create a barebone adapter that inherits from JdbcAdapter.

| It is a good idea to put all new adapter code in its own Java package, e.g. `org.apache.cayenne.dba.mydb`, as default resource loading depends on that.

- Copy `types.xml` file from org.apache.cayenne.dba package and edit it to map standard JDBC types to the target database native types.

| Correct mapping is needed for the Modeler to do schema generation. Technically it is not required for the runtime. However `types.xml` should still be there.

- Run existing Cayenne unit tests with the new adapter, analyze the failures and change adapter code accordingly.
- Repeat the last step until all tests pass.
- Report success in JIRA and the dev list - one of the committers will integrate your code to Cayenne.

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