com.luciad.format.oracle.spatial

Database ConnectorsClass TLcdOracleSpatialModelDecoder

java.lang.Object

com.luciad.format.oracle.spatial.TLcdOracleSpatialModelDecoder

All Implemented Interfaces:

ILcdModelDecoder

@LcdService(priority=20000)
public class TLcdOracleSpatialModelDecoder
extends Object
implements ILcdModelDecoder

This model decoder decodes spatial tables from Oracle Spatial Object-Relational databases.

Input files

File	Required	Entry point	Description
*.ora		x	Java properties file containing all the necessary properties to access the spatial data

Alternatively, a Properties object can be constructed programmatically and passed to the model decoder.

The common properties needed to establish a connection are:

• driver (default = oracle.jdbc.driver.OracleDriver): the JDBC driver that will be used to connect to the database.
• url: the database URL.
• user: the database user name.
• password: the user's password.

Other JDBC properties that can help to tune the database connection are passed on to JDBC as well.

The properties that identify the tables, columns, rows, etc. within the database are:

• table: the name of the table containing the geometries.
• spatialColumn: the column containing the geometries.
• spatialQueryColumn: an optional column containing the geometries that should be used in spatial queries. By default, this column is equal to the spatialColumn. It should not be changed for most typical applications.
• featureNames.0, ...: the column names that should be retrieved as object features in the model. For read-only models, more complex SQL expressions, or columns from selection tables (see below) are accepted too.
• featureDisplayNames.0, ...: optional display names corresponding to the feature names.
• primaryFeatureIndex (default = 0): the index of the feature that serves as a primary key.
• primaryFeatureAutoGenerated (default = false): specifies whether the database automatically generates the primary key whenever a geometry is inserted into the spatial table. The primary feature on the java side will then be updated with this generated value.
• selectionTables (default = null): an optional comma-separated list of tables required to constrain the geometries of the model. These tables will be added after the main table in the FROM parts of SELECT queries. Note that any column names that are ambiguous (because they occur in multiple tables), have to be prefixed with the suitable table names.
• selectionFilter (default = null): an optional SQL select query to constrain the geometries of the model. This query will be added after the spatial query in the WHERE parts of SELECT queries.

Supported transfer protocols

• This model decoder supports all protocols that are supported by the underlying JDBC driver.

Model structure

• This model decoder creates a model per spatial table.
• All models returned by this model decoder implement ILcd2DBoundsIndexedModel.

Model descriptor

• The model descriptor of a decoded model is a TLcdOracleSpatialModelDescriptor.

Three optional properties allow to override some metadata in the model descriptor:

• sourceName (default = the source name that is passed to the model decoder): the source name of the model descriptor.
• typeName (default = the display name of the model decoder): the type name of the model descriptor. The type name is also used when composing the name of the data model.
• displayName (default = the spatial table name): the display name of the model descriptor. The display name is also used when composing the name of the data model and the name of the data type.

Model reference

By default, the model reference of a decoded model is determined by the SRID of the spatial table. Oracle Spatial requires that the SRID is set in the USER_SDO_GEOM_METADATA table and in the geometries themselves. If no model reference can be created the default model reference set on this decoder will be used (see setDefaultModelReference(com.luciad.model.ILcdModelReference)).

Model elements

• This decoded database models contain 2D or 3D ILcdShape objects:

  FROM Geometry	TO ILcdShape
  Point	ILcdPoint
  Point cluster	ILcdPolypoint
  Line	ILcdPolyline
  Arc	ILcdArc
  Line string (straight)	ILcdPolyline
  Line string (arcs)	ILcdShapeList
  Polygon (straight)	ILcdPolygon
  Polygon (straight)	ILcdComplexPolygon
  Polygon (arcs)	ILcdShapeList
  Rectangle	ILcdBounds
  Circle	ILcdCircle
  Compound line string	ILcdShapeList
  Compound polygon	ILcdShapeList
  Box	ILcdBounds
  Surface	ILcdShapeList
  Solid	ILcdShapeList

• The elements also implement the ILcdFeatured interface and the ILcdDataObject interface, providing access to their features.

Useful settings

• The decoder property readOnly can be set to specify whether the model will be used as a read-only model.

Sample code

 ILcdModelDecoder decoder =
   new TLcdOracleSpatialModelDecoder(true);

 ILcdModel model = decoder.decode("countries.ora");
 

The file countries.ora could for instance contain the following properties:

 # The basic database connection properties.
 driver    = oracle.jdbc.driver.OracleDriver
 url       = jdbc:oracle:thin:@myhost:1521:LUCIAD
 user      = scott
 password  = tiger

 # The data of interest.
 table         = COUNTRIES
 spatialColumn = GEOM

 # The feature columns to be decoded.
 featureNames.0 = ID

 # The index of the feature that can be used as primary key.
 primaryFeatureIndex = 0

 # Optional extra tables and SQL condition to restrict the database elements.
 # Note that the above feature names also have to be prefixed with the table
 # name if the column names are ambiguous, like the ID column below.
 #selectionTables = POPULATION
 #selectionFilter = COUNTRIES.ID = POPULATION.ID AND POPULATION.VALUE > 1e7

 # Optional maximum cache size (expressed as number of objects, default is 100).
 maxCacheSize = 500

 # Optionally close the database connection after each query.
 # Only advisable when using a connection pooling database driver.
 #alwaysCloseConnection = false
 

Performance tips

Some optional properties in the properties file or object can help to tune the database access:

• hints (default = null): an optional string containing Oracle SQL hints that should be used in all spatial and non-spatial queries of the decoded database model. The hints will be enclosed in /*+ and */ comment delimiters in the SELECT statements that are performed internally. Note that hints should be used sparingly, as discussed in Oracle's SQL Language Reference.
• alwaysCloseConnection (default = false): an optional boolean to specify that the database connection should be closed after each query. Setting this flag can be useful for database drivers that pool connections, so the connections are reused instead of really being closed.
• maxCacheSize (default = 100, or the value set on the decoder): the maximum number of objects in the cache. Using a cache will improve performance if transferring and decoding geometries and their features is relatively expensive compared to performing the original SQL queries. The current implementation of the decoder will then perform queries in two passes, first retrieving the relevant primary keys and then retrieving and decoding the actual geometries and features that are not in the cache. On the other hand, setting the cache size to 0 may be better if performing SQL queries is relatively expensive. The current implementation of the decoder will then perform queries in a single pass, retrieving and decoding the relevant geometries every time.

Thread safety

• The decoding of models is thread-safe, as long as no properties are changed during the decoding.
• The decoded models are thread-safe for read access.

Supported versions and specifications

• Oracle 8/9i/10g/11g Spatial Object-Relational.

Known limitations

• Some rare SRID model references are not supported.
• Updating database views and data sets involving additional tables is generally not possible.

Constructor Summary

Constructors

Constructor and Description
TLcdOracleSpatialModelDecoder() Creates a new, read-write, Oracle Spatial model decoder.
TLcdOracleSpatialModelDecoder(boolean aReadOnly) Creates a new Oracle Spatial model decoder.

Method Summary

Modifier and Type	Method and Description
boolean	canDecodeSource(String aSourceAsString) Checks whether this model decoder can decode the specified data source.
ILcdModel	decode(Properties aProperties) Decodes a new database model based on the given properties.
ILcdModel	decode(String aSourceName) Decodes a new database model based on the properties specified in the given file.
int	getDefaultMaxCacheSize()
ILcdModelReference	getDefaultModelReference() Returns the default model reference to be assigned to decoded models.
String	getDisplayName() Returns a short, displayable name for the format that is decoded by this ILcdModelDecoder.
boolean	getReadOnly()
void	setDefaultMaxCacheSize(int aDefaultMaxCacheSize) Sets the default maximum size of the cache.
void	setDefaultModelReference(ILcdModelReference aDefaultModelReference) Sets the default model reference to be assigned to decoded models if no model reference can be created based on information from the database.
void	setReadOnly(boolean aReadOnly) Specifies whether the decoded models should be read-only or not.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.luciad.model.ILcdModelDecoder

canDecodeSource, decodeModelMetadata, decodeModelMetadata, decodeSource, discoverDataSources

Constructor Detail

TLcdOracleSpatialModelDecoder

public TLcdOracleSpatialModelDecoder()

Creates a new, read-write, Oracle Spatial model decoder.

TLcdOracleSpatialModelDecoder

public TLcdOracleSpatialModelDecoder(boolean aReadOnly)

Creates a new Oracle Spatial model decoder.

Parameters:

aReadOnly - specifies the type of models the decoder should construct.

See Also:

setReadOnly(boolean)

Method Detail

setDefaultModelReference

public void setDefaultModelReference(ILcdModelReference aDefaultModelReference)

Sets the default model reference to be assigned to decoded models if no model reference can be created based on information from the database.

Parameters:

aDefaultModelReference - the default model reference.

See Also:

getDefaultModelReference()

getDefaultModelReference

public ILcdModelReference getDefaultModelReference()

Returns the default model reference to be assigned to decoded models.

Returns:

the default model reference.

See Also:

setDefaultModelReference(com.luciad.model.ILcdModelReference)

setDefaultMaxCacheSize

public void setDefaultMaxCacheSize(int aDefaultMaxCacheSize)

Sets the default maximum size of the cache. It is possible to override this value by means of the maxCacheSize property in the properties file.

Parameters:

aDefaultMaxCacheSize - the default maximum number of objects in the cache.

getDefaultMaxCacheSize

public int getDefaultMaxCacheSize()

setReadOnly

public void setReadOnly(boolean aReadOnly)

Specifies whether the decoded models should be read-only or not.

Parameters:

aReadOnly - specifies the type of models the decoder should construct. If true, the decoder will create TLcdDatabaseReadOnlyModel objects. If false, the decoder will create TLcdDatabaseModel objects.

getReadOnly

public boolean getReadOnly()

getDisplayName

public String getDisplayName()

Description copied from interface: ILcdModelDecoder

Returns a short, displayable name for the format that is decoded by this ILcdModelDecoder.

Specified by:

getDisplayName in interface ILcdModelDecoder

Returns:

the displayable name of this ILcdModelDecoder.

canDecodeSource

public boolean canDecodeSource(String aSourceAsString)

Description copied from interface: ILcdModelDecoder

Checks whether this model decoder can decode the specified data source. It is acceptable for this method to return true for a source name while decode throws an exception for that same source name.

For performance reasons, we strongly recommend that this will only be a simple test. For example: check the file extension of a file, but not that the file exists or contains expected content.

Specified by:

canDecodeSource in interface ILcdModelDecoder

Parameters:

aSourceAsString - the data source to be verified; typically a file name or a URL.

Returns:

true if this decoder can likely decode the data specified by the source name, false otherwise.

See Also:

ILcdModelDecoder.decode(String), ILcdModelDecoder.decodeModelMetadata(String)

decode

public ILcdModel decode(String aSourceName)
                 throws IOException

Decodes a new database model based on the properties specified in the given file.

Specified by:

decode in interface ILcdModelDecoder

Parameters:

aSourceName - the data source to be decoded; typically a file name or a URL.

Returns:

A model containing the decoded data. While null is allowed, implementors are advised to throw an error instead.

Throws:

IOException - for any exceptions caused by IO problems or invalid data. Since decoding invalid data almost always results in RunTimeExceptions (NullPointerException, IndexOutOfBoundsException, IllegalArgumentException, ...) on unexpected places, implementations are advised to catch RuntimeExceptions in their decode() method, and wrap them into an IOException, as illustrated in the code snippet below.

   public ILcdModel decode( String aSourceName ) throws IOException {
      try (InputStream input = fInputStreamFactory.createInputStream(aSourceName)) {
         // Perform decoding ...
      } catch (RuntimeException e) {
         throw new IOException(e);
      }
   }
 

InterruptedIOException - When the thread on which this method is called is interrupted: it is recommended to stop the decoding and throw an InterruptedIOException. This same exception can also be used if the decoder shows UI to the user, and the user cancels the decoding through the UI.

See Also:

ILcdModelDecoder.canDecodeSource(String)

decode

public ILcdModel decode(Properties aProperties)
                 throws IOException

Decodes a new database model based on the given properties.

Throws:

IOException