org.geotools.data

Interface DataAccess<T extends FeatureType,F extends Feature>

Type Parameters:

T - Type of Feature Content, may be SimpleFeatureType

F - Feature Content, may be SimpleFetaure

All Known Subinterfaces:

DataStore, FileDataStore

All Known Implementing Classes:

AppSchemaDataAccess, ArcSDEDataStore, ContentDataStore, DataStoreWrapper, DecoratingDataStore, DirectoryDataStore, JDBCDataStore, MemoryDataStore, MongoDataStore, OracleDatastoreWrapper, PostgisDatastoreWrapper, PreGeneralizedDataStore, PropertyDataStore, SampleDataAccess, ShapefileDataStore, SingleFeatureSourceDataStore, WFSContentDataAccess, WFSDataStore

public interface DataAccess<T extends FeatureType,F extends Feature>

This is the top-level interface for access to FeatureData.

Description

The DataAccess interface provides the following information about its contents:

• DataAccess.getInfo() - information about the file or server itself
• DataAccess.getNames() - list of the available contents (each is an individual resource)
• DataAccess.getSchema( Name ) - FeatureType describing the information available in the named resource

Contents

You can access the contents of a service or file using getFeatureSource( Name ). Depending the abilities of your implementation and your credentials you will have access to

• FeatureSource: read-only api similar to the WFS getFeature operations. Please note the reutrned FeatureCollection may be *lazy*; for many implementations no actual access will occur until you use the FetaureCollection for the first time.
• FeatureStore: read/write api similar to the WFS Transaction operation. Batch changes such as addFeatures, modifyFeatures and removeFeatures are supported.
• FeatureLocking: concurrency control; the Data Access API is thread safe; one consequence of this is modifications being held up while other threads read the contents. You may wish to Lock a selection of features for your exclusive use. Locks are timed; and will expire after the indicated period.

Please note that all interaction occurs within the context of a Transaction, this facility provides session management and is strongly advised. Please note that your application is responsible for managing its own Transactions; as an example they are often associated with a single Map in a desktop application; or a single session in a J2EE web app.

The use of Transaction.AUTO_COMMIT is suitable for read-only access when you wish to minimize the number of connections in use, when used for writing performance will often be terrible.

Lifecycle

Normal use:

• Connect using a DataAccessFactory.createDataStore using a set of connection parameters
• Application is responsible for holding a single instance to the service or file, DataAccess implementations will hold onto database connections, internal caches and so on - and as such should not be duplicated.
• DataAccess.dispose() is called when the application is shut down

Creation:

• Created using a DataAccessFactory.createNewDataStore using a set of creation parameters
• DataAccess.createSchema( T ) is called to set up the contents
• DataAccess.getFetaureSource( Name ) is called, and FeatureStore.addFeatures( collection ) used to populate the contents
• DataAccess.dispose() is called when the application is shut down

Applications are responsible for holding a single instance to the service or file, The DataAccess implementations will hold onto database connections, internal caches and so on - and as such should not be duplicated.

See Also:

Subclass restricted to working with simple content

Method Summary

Modifier and Type	Method and Description
void	createSchema(T featureType) Creates storage for a new featureType.
void	dispose() Disposes of this data store and releases any resource that it is using.
FeatureSource<T,F>	getFeatureSource(Name typeName) Access to the named resource.
ServiceInfo	getInfo() Information about this service.
List<Name>	getNames() Names of the available Resources.
T	getSchema(Name name) Description of the named resource.
void	removeSchema(Name typeName) Used to permanently remove a schema from the underlying storage This functionality is similar to an "drop table" statement in SQL.
void	updateSchema(Name typeName, T featureType) Used to update a schema in place.

Method Detail

getInfo

ServiceInfo getInfo()

Information about this service.

This method offers access to a summary of header or metadata information describing the service. Subclasses may return a specific ServiceInfo instance that has additional information (such as FilterCapabilities).

Returns:

SeviceInfo

createSchema

void createSchema(T featureType)
           throws IOException

Creates storage for a new featureType.

The provided featureType we be accessable by the typeName provided by featureType.getTypeName().

Parameters:

featureType - FetureType to add to DataStore

Throws:

IOException - If featureType cannot be created

updateSchema

void updateSchema(Name typeName,
                  T featureType)
           throws IOException

Used to update a schema in place.

This functionality is similar to an "alter table" statement in SQL. Implementation is optional; it may not be supported by all servers or files.

Parameters:

typeName -

featureType -

Throws:

IOException - if the operation failed

UnsupportedOperation - if functionality is not available

removeSchema

void removeSchema(Name typeName)
           throws IOException

Used to permanently remove a schema from the underlying storage

This functionality is similar to an "drop table" statement in SQL. Implementation is optional; it may not be supported by all servers or files.

Parameters:

typeName -

Throws:

IOException - if the operation failed

UnsupportedOperation - if functionality is not available

getNames

List<Name> getNames()
             throws IOException

Names of the available Resources.

For additional information please see getInfo( Name ) and getSchema( Name ).

Returns:

Names of the available contents.

Throws:

IOException

getSchema

T getSchema(Name name)
     throws IOException

Description of the named resource.

The FeatureType returned describes the contents being published. For additional metadata please review getInfo( Name ).

Parameters:

name - Type name a the resource from getNames()

Returns:

Description of the FeatureType being made avaialble

Throws:

IOException

getFeatureSource

FeatureSource<T,F> getFeatureSource(Name typeName)
                             throws IOException

Access to the named resource.

The level of access is represented by the instance of the FeatureSource being returned.

Formally:

• FeatureSource - read-only access
• FeatureStore - read-write access
• FetureLocking - concurrency control
  Additional interfaces may be supported by the implementation you are using.

Parameters:

typeName -

Returns:

Access to the named resource being made available

Throws:

IOException

dispose

void dispose()

Disposes of this data store and releases any resource that it is using.

A DataStore cannot be used after dispose has been called, neither can any data access object it helped create, such as FeatureReader, FeatureSource or FeatureCollection.

This operation can be called more than once without side effects.

There is no thread safety assurance associated with this method. For example, client code will have to make sure this method is not called while retrieving/saving data from/to the storage, or be prepared for the consequences.