Client and backend. This class is shared: the same code is compiled into your app and into your server, so everything on this page works in both.

public interface MigrationContext

What a JavaMigration may do to the database it is migrating.

Methods

`public abstract` `String dialect()`	The engine being migrated.
`public abstract void execute(String sql, Object[] params) throws IOException`	Runs one statement.
`public abstract` `List<String[]> query(String sql, Object[] params) throws IOException`	Runs one query and returns every row with every value as text, null where the column is null.
`public abstract` `Object connection()`	The runtime’s own database object: `com.codename1.db.Database` in an application, `com.codename1.backend.Database` on a server.

Method details

dialect

public abstract String dialect()

The engine being migrated.

Returns

sqlite, postgresql or mysql; MariaDB answers mysql

execute

public abstract void execute(String sql, Object[] params)
throws IOException

Runs one statement.

Parameters

sql String: a single statement, with ? for each parameter
params Object[]: the parameter values, or null for none

Throws

IOException: if the database refuses it

query

public abstract List<String[]> query(String sql, Object[] params)
throws IOException

Runs one query and returns every row with every value as text, null where the column is null. Text is the one representation every engine and both runtimes agree on; a migration that needs typed access uses connection().

Parameters

sql String: a single query, with ? for each parameter
params Object[]: the parameter values, or null for none

Returns

the rows in order

Throws

IOException: if the database refuses it

connection

public abstract Object connection()

The runtime’s own database object: com.codename1.db.Database in an application, com.codename1.backend.Database on a server. Test it with instanceof before casting.

Returns

the connection the migration runs on