org.apache.metamodel

Class AbstractDataContext

java.lang.Object

org.apache.metamodel.AbstractDataContext

All Implemented Interfaces:

DataContext

Direct Known Subclasses:

CompositeDataContext, JdbcDataContext, OpenOfficeDataContext, QueryPostprocessDataContext

public abstract class AbstractDataContext
extends Object
implements DataContext

Abstract implementation of the DataContext interface. Provides convenient implementations of all trivial and datastore-independent methods.

Constructor Summary

Constructors

Constructor and Description
AbstractDataContext()

Method Summary

Methods

Modifier and Type	Method and Description
CompiledQuery	compileQuery(Query query) Compiles a query, preparing it for reuse.
DataSet	executeQuery(CompiledQuery compiledQuery, Object... values) Executes a compiled query with given values as parameters.
DataSet	executeQuery(String queryString) Parses and executes a string-based SQL query.
Column	getColumnByQualifiedLabel(String columnName) Finds a column in the DataContext based on a fully qualified column label.
Schema	getDefaultSchema() Gets the default schema of this DataContext.
protected abstract String	getDefaultSchemaName() Gets the name of the default schema.
Schema	getSchemaByName(String name) Gets a schema by a specified name.
protected abstract Schema	getSchemaByNameInternal(String name) Gets a specific schema from the non-abstract implementation.
String[]	getSchemaNames() m Gets the names of all schemas within this DataContext.
protected abstract String[]	getSchemaNamesInternal() Gets schema names from the non-abstract implementation.
Schema[]	getSchemas() Gets all schemas within this DataContext.
Table	getTableByQualifiedLabel(String tableName) Finds a table in the DataContext based on a fully qualified table label.
protected boolean	isQualifiedPathDelim(char c)
protected void	onSchemaCacheRefreshed() Method invoked when schemas have been refreshed using refreshSchemas().
Query	parseQuery(String queryString) Parses a string-based SQL query and produces a corresponding Query object.
InitFromBuilder	query() Starts building a query using the query builder API.
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

Methods inherited from interface org.apache.metamodel.DataContext

executeQuery

Constructor Detail

AbstractDataContext

public AbstractDataContext()

Method Detail

refreshSchemas

public final DataContext refreshSchemas()

Enforces a refresh of the schemas. If not refreshed, cached schema objects may be used.

Specified by:

refreshSchemas in interface DataContext

Returns:

this DataContext

onSchemaCacheRefreshed

protected void onSchemaCacheRefreshed()

Method invoked when schemas have been refreshed using refreshSchemas(). Can be overridden to add callback functionality in subclasses.

getSchemas

public final Schema[] getSchemas()
                          throws MetaModelException

Gets all schemas within this DataContext.

Specified by:

getSchemas in interface DataContext

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 final String[] getSchemaNames()
                              throws MetaModelException

m Gets the names of all schemas within this DataContext.

Specified by:

getSchemaNames in interface DataContext

Returns:

an array of valid schema names

Throws:

MetaModelException - if an error occurs retrieving the schema model

getDefaultSchema

public final Schema getDefaultSchema()
                              throws MetaModelException

Gets the default schema of this DataContext.

Specified by:

getDefaultSchema in interface DataContext

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

query

public final InitFromBuilder query()

Starts building a query using the query builder API. This way of building queries is the preferred approach since it provides a more type-safe approach to building API's as well as allows the DataContext implementation to be aware of the query building process.

Specified by:

query in interface DataContext

Returns:

a query builder component at the initial position in building a query.

parseQuery

public Query parseQuery(String queryString)
                 throws MetaModelException

Parses a string-based SQL query and produces a corresponding Query object.

Specified by:

parseQuery in interface DataContext

Parameters:

queryString - the SQL query to parse

Returns:

a Query object corresponding to the SQL query.

Throws:

MetaModelException - in case the parsing was unsuccesful.

compileQuery

public CompiledQuery compileQuery(Query query)
                           throws MetaModelException

Description copied from interface: DataContext

Compiles a query, preparing it for reuse. Often times compiled queries have a performance improvement when executed, but at the cost of a preparation time penalty. Therefore it is adviced to use compiled queries when the same query is to be fired multiple times. Compiled queries can contain QueryParameters as operands in the WHERE clause, making it possible to reuse the same query with different parameter values.

Specified by:

compileQuery in interface DataContext

Parameters:

query - the query object to execute, possibly holding one or more QueryParameters.

Returns:

the CompiledQuery after preparing the query

Throws:

MetaModelException - if preparing the query is unsuccesful

See Also:

CompiledQuery, QueryParameter

executeQuery

public DataSet executeQuery(CompiledQuery compiledQuery,
                   Object... values)

Description copied from interface: DataContext

Executes a compiled query with given values as parameters.

Specified by:

executeQuery in interface DataContext

Parameters:

compiledQuery - the compiledQuery object to execute

values - the values for parameters in the CompiledQuery.

Returns:

the DataSet produced from executing the query.

executeQuery

public final DataSet executeQuery(String queryString)
                           throws MetaModelException

Parses and executes a string-based SQL query. This method is essentially equivalent to calling first DataContext.parseQuery(String) and then DataContext.executeQuery(Query) with the parsed query.

Specified by:

executeQuery in interface DataContext

Returns:

the DataSet produced from executing the query

Throws:

MetaModelException - if either parsing or executing the query produces an exception

getSchemaByName

public final Schema getSchemaByName(String name)
                             throws MetaModelException

Gets a schema by a specified name.

Specified by:

getSchemaByName in interface DataContext

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

getColumnByQualifiedLabel

public final Column getColumnByQualifiedLabel(String columnName)

Finds a column in the DataContext based on a fully qualified column label. The qualified label consists of the the schema, table and column name, delimited by a dot (.).

Specified by:

getColumnByQualifiedLabel in interface DataContext

Returns:

a column that matches the qualified label, or null if no such column exists

getTableByQualifiedLabel

public final Table getTableByQualifiedLabel(String tableName)

Finds a table in the DataContext based on a fully qualified table label. The qualified label consists of the the schema and table name, delimited by a dot (.).

Specified by:

getTableByQualifiedLabel in interface DataContext

Returns:

a table that matches the qualified label, or null if no such table exists

isQualifiedPathDelim

protected boolean isQualifiedPathDelim(char c)

getSchemaNamesInternal

protected abstract String[] getSchemaNamesInternal()

Gets schema names from the non-abstract implementation. These schema names will be cached except if the refreshSchemas() method is called.

Returns:

an array of schema names.

getDefaultSchemaName

protected abstract String getDefaultSchemaName()

Gets the name of the default schema.

Returns:

the default schema name.

getSchemaByNameInternal

protected abstract Schema getSchemaByNameInternal(String name)

Gets a specific schema from the non-abstract implementation. This schema object will be cached except if the refreshSchemas() method is called.

Parameters:

name - the name of the schema to get

Returns:

a schema object representing the named schema, or null if no such schema exists.