public interface DataAccessFactory extends Factory
The following example shows how a user might connect to a PostGIS database, and maintain the resulting datastore in a Registry:
The required parameters are described by the getParameterInfo() method. Client
HashMap params = new HashMap(); params.put("namespace", "leeds"); params.put("dbtype", "postgis"); params.put("host","feathers.leeds.ac.uk"); params.put("port", "5432"); params.put("database","postgis_test"); params.put("user","postgis_ro"); params.put("passwd","postgis_ro"); DefaultRegistry registry = new DefaultRegistry(); registry.addDataStore("leeds", params); DataStore postgis = registry.getDataStore( "leeds" ); SimpleFeatureSource = postgis.getFeatureSource( "table" );
An instance of this interface should exist for all DataAccess implementations that want to advantage of the dynamic plug-in system. In addition to implementing this interface a DataAccess implementation should provide a services file:
The file should contain a single line which gives the full name of the implementing class.
The factories are never called directly by client code, instead the DataStoreFinder class is used.
|Modifier and Type||Interface and Description|
Data class used to capture Parameter requirements.
|Modifier and Type||Method and Description|
Test to see if this factory is suitable for processing the data pointed to by the params map.
Construct a live DataAccess using the connection parameters provided.
Describe the nature of the datasource constructed by this factory.
Name suitable for display to end user.
MetaData about the required Parameters (for createDataStore).
Test to see if the implementation is available for use.
DataAccess<? extends FeatureType,? extends Feature> createDataStore(Map<String,Serializable> params) throws IOException
You can think of this class as setting up a connection to the back end data source. The required parameters are described by the getParameterInfo() method.
Magic Params: the following params are magic and are honoured by convention by the GeoServer and uDig application.
params- The full set of information needed to construct a live data store. Typical key values for the map include: url - location of a resource, used by file reading datasources. dbtype - the type of the database to connect to, e.g. postgis, mysql
IOException- if there were any problems setting up (creating or connecting) the datasource.
A non localized display name for this data store type.
A non localized description of this data store type.
Interpretation of FeatureDescriptor values:
This should be the same as:
Object params = factory.getParameters(); BeanInfo info = getBeanInfo( params ); return info.getPropertyDescriptors();
boolean canProcess(Map<String,Serializable> params)
If this datasource requires a number of parameters then this mehtod should check that they are all present and that they are all valid. If the datasource is a file reading data source then the extentions or mime types of any files specified should be checked. For example, a Shapefile datasource should check that the url param ends with shp, such tests should be case insensative.
params- The full set of information needed to construct a live data source.
Most factories will simply return
true as GeoTools will
distribute the appropriate libraries. Though it's not a bad idea for
DataStoreFactories to check to make sure that the libraries are there.
OracleDataStoreFactory is an example of one that may generally return
false, since GeoTools can not distribute the oracle jars.
(they must be added by the client.)
One may ask how this is different than canProcess, and basically available is used by the DataStoreFinder getAvailableDataStore method, so that DataStores that can not even be used do not show up as options in gui applications.
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