Create database plugins

A database plugin introduces a new entry in the PDI database dialog box.

This section explains the architecture and programming concepts for creating your own database plugin. We recommend that you open and refer to the sample database plugin sources while following these instructions.

• Java Interface

  org.pentaho.di.core.database.DatabaseInterface

• Base class

  org.pentaho.di.core.database.BaseDatabaseMeta

PDI database plugins consist of a single Java class that implements the interface org.pentaho.di.core.database.DatabaseInterface.

In order for PDI to recognize the database plugin, the class implementing DatabaseInterface must also be annotated with the Java annotation org.pentaho.di.core.plugins.DatabaseMetaPlugin.

Supply these annotation attributes.

• type

  A globally unique ID for database plugin

• typeDescription

  The label to use in the database dialog box

It is recommended to extend org.pentaho.di.core.database.BaseDatabaseMeta, which provides default implementations for most of the methods in DatabaseInterface. Existing PDI database interfaces are a great source of information when developing a new database plugin.

The following section classifies some of the most commonly overridden methods. They can be roughly classified into three subject areas: information about connections, SQL dialect, and general capability flags.

These methods are called when PDI establishes a connection to the database, or the database dialog is populated with database-specific defaults.

• public String getDriverClass()
• public int getDefaultDatabasePort()
• public int[] getAccessTypeList()
• public boolean supportsOptionsInURL()
• public String getURL()

These methods are called when PDI constructs SQL.

• public String getFieldDefinition()
• public String getAddColumnStatement()
• public String getSQLColumnExists()
• public String getSQLQueryFields()

These methods are called when PDI determines the run-time characteristics of the database system. For instance, the database systems may support different notions of metadata retrieval.

• public boolean supportsTransactions()
• public boolean releaseSavepoint()
• public boolean supportsPreparedStatementMetadataRetrieval()
• public boolean supportsResultSetMetadataRetrievalOnly()

PDI sources are invaluable when seeking example implementations of databases. Each of the PDI core database support classes is located in the org.pentaho.di.core.database package found in the core/src folder.

For example, here are the classes that define behavior for some major database systems.

When implementing a database plugin for a new database system, we recommended starting from an existing database class that already shares characteristics with the new database system.