dk.eobjects.metamodel
Class DataContext

java.lang.Object
  dk.eobjects.metamodel.DataContext

public class DataContext
extends java.lang.Object

A DataContext represents the central entry point for interactions with datastores. The DataContext contains of the structure of data (in the form of schemas) and interactions (in the form of queries) with data.

Constructor Summary

DataContext(IDataContextStrategy strategy)
Creates a DataContext based on a specified IDataContextStrategy.

Method Summary

DataSet	executeQuery(Query query) Executes a query against the data context.
Schema	getDefaultSchema()
Schema	getSchemaByName(java.lang.String name) Gets a schema by a specified name
java.lang.String[]	getSchemaNames()
Schema[]	getSchemas()
DataContext	refreshSchemas() Enforces a refresh of the schemas.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DataContext

public DataContext(IDataContextStrategy strategy)

Creates a DataContext based on a specified IDataContextStrategy. This enables development of custom datastore formats, by developing your own strategy-objects.

Parameters:

strategy -

Method Detail

refreshSchemas

public DataContext refreshSchemas()

Enforces a refresh of the schemas.

getSchemas

public Schema[] getSchemas()
                    throws MetaModelException

Returns:

the schemas in this data context. Schemas are cached for reuse in many situations so if you want to update the schemas, use the refreshSchemas() method.

Throws:

MetaModelException - if an error occurs retrieving the schema model

getSchemaNames

public java.lang.String[] getSchemaNames()
                                  throws MetaModelException

Returns:

an array of valid schema names

Throws:

MetaModelException - if an error occurs retrieving the schema model

getDefaultSchema

public Schema getDefaultSchema()
                        throws MetaModelException

Returns:

the schema that you are most probable to be interested in. The default schema is determined by finding the schema with most available of tables. In a lot of situations there will only be a single available schema and in that case this will of course be the schema returned.

Throws:

MetaModelException - if an error occurs retrieving the schema model

getSchemaByName

public Schema getSchemaByName(java.lang.String name)
                       throws MetaModelException

Gets a schema by a specified name

Parameters:

name - the name of the desired schema

Returns:

the Schema with the specified name or null if no such schema exists

Throws:

MetaModelException - if an error occurs retrieving the schema model

executeQuery

public DataSet executeQuery(Query query)
                     throws MetaModelException

Executes a query against the data context.

Parameters:

query - the query object to execute

Returns:

the dataset produced from executing the query

Throws:

MetaModelException - if the specified query does not make sense or cannot be executed because of restraints on the type of datastore.