1. A method in a data processing system for providing a single set of object relational mappings across different instances of the same schemas, comprising: configuring multiple datasources for a class; setting a mapping identifier at runtime, wherein the mapping identifier is used to access a particular datasource; generating mapping code from the particular datasource based on the mapping identifier; acquiring a schema identifier from the generated mapping code; prepending the schema identifier to tables in a SQL generated code; and using a schema name associated with the schema identifier to connect to a schema instance in the particular datasource.