Package org.geotools.api.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, ContentDataStore, CSVDataStore, DataStoreWrapper, DecoratingDataStore, DirectoryDataStore, GeoJSONDataStore, GraticuleDataStore, JDBCDataStore, MBTilesDataStore, MemoryDataStore, MongoDataStore, OGRDataStore, OracleDatastoreWrapper, PostgisDatastoreWrapper, PreGeneralizedDataStore, PropertyDataStore, SampleDataAccess, ShapefileDataStore, SingleFeatureSourceDataStore, SQLServerDatastoreWrapper, STACDataStore, VectorMosaicStore, VPFFileStore, VPFLibrary, 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:
    • getInfo() - information about the file or server itself
    • getNames() - list of the available contents (each is an individual resource)
    • 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 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.

        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.

        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.
        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.