/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2003-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.data;
import java.io.IOException;
import java.io.Serializable;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.geotools.factory.FactoryCreator;
import org.geotools.factory.FactoryRegistry;
import org.opengis.feature.Feature;
import org.opengis.feature.type.FeatureType;
/**
* Enable programs to find all available DataAccess implementations, including
* the DataStore ones.
*
* <p>
* In order to be located by this finder datasources must provide an
* implementation of the {@link DataAccessFactory} interface.
* </p>
*
* <p>
* In addition to implementing this interface datasouces should have a services
* file:<br/><code>META-INF/services/org.geotools.data.DataAccessFactory</code>
* </p>
*
* <p>
* The file should contain a single line which gives the full name of the
* implementing class.
* </p>
*
* <p>
* Example:<br/><code>org.geotools.data.mytype.MyTypeDataAccessFacotry</code>
* </p>
*
*
* @source $URL$
*/
public final class DataAccessFinder {
/** The logger for the filter module. */
protected static final Logger LOGGER = org.geotools.util.logging.Logging
.getLogger("org.geotools.data");
/**
* The service registry for this manager. Will be initialized only when
* first needed.
*/
private static FactoryRegistry registry;
// Singleton pattern
private DataAccessFinder() {
}
/**
* Checks each available datasource implementation in turn and returns the
* first one which claims to support the resource identified by the params
* object.
*
* @param params
* A Map object which contains a defenition of the resource to
* connect to. for file based resources the property 'url' should
* be set within this Map.
*
* @return The first datasource which claims to process the required
* resource, returns null if none can be found.
*
* @throws IOException
* If a suitable loader can be found, but it can not be attached
* to the specified resource without errors.
*/
public static synchronized DataAccess<FeatureType, Feature> getDataStore(
Map<String, Serializable> params) throws IOException {
Iterator<DataAccessFactory> ps = getAvailableDataStores();
return (DataAccess<FeatureType, Feature>) getDataStore(params, ps);
}
static DataAccess<? extends FeatureType, ? extends Feature> getDataStore(
Map<String, Serializable> params, Iterator<? extends DataAccessFactory> ps)
throws IOException {
DataAccessFactory fac;
IOException canProcessButNotAvailable = null;
while (ps.hasNext()) {
fac = (DataAccessFactory) ps.next();
boolean canProcess = false;
try {
canProcess = fac.canProcess(params);
} catch (Throwable t) {
LOGGER.log(Level.WARNING, "Problem asking " + fac.getDisplayName()
+ " if it can process request:" + t, t);
// Protect against DataStores that don't carefully code
// canProcess
continue;
}
if (canProcess) {
boolean isAvailable = false;
try {
isAvailable = fac.isAvailable();
} catch (Throwable t) {
LOGGER.log(Level.WARNING, "Difficulity checking if " + fac.getDisplayName()
+ " is available:" + t, t);
// Protect against DataStores that don't carefully code
// isAvailable
continue;
}
if (isAvailable) {
try {
return fac.createDataStore(params);
} catch (IOException couldNotConnect) {
canProcessButNotAvailable = couldNotConnect;
LOGGER.log(Level.WARNING, fac.getDisplayName()
+ " should be used, but could not connect", couldNotConnect);
}
} else {
canProcessButNotAvailable = new IOException(
fac.getDisplayName()
+ " should be used, but is not availble. Have you installed the required drivers or jar files?");
LOGGER.log(Level.WARNING, fac.getDisplayName()
+ " should be used, but is not availble", canProcessButNotAvailable);
}
}
}
if (canProcessButNotAvailable != null) {
throw canProcessButNotAvailable;
}
return null;
}
/**
* Finds all implemtaions of DataAccessFactory which have registered using
* the services mechanism, regardless weather it has the appropriate
* libraries on the classpath.
*
* @return An iterator over all discovered datastores which have registered
* factories
*/
public static synchronized Iterator<DataAccessFactory> getAllDataStores() {
Set<DataAccessFactory> all = new HashSet<DataAccessFactory>();
Iterator<DataStoreFactorySpi> allDataStores = DataStoreFinder.getAllDataStores();
Iterator<DataAccessFactory> allDataAccess = getAllDataStores(getServiceRegistry(),
DataAccessFactory.class);
while (allDataStores.hasNext()) {
DataStoreFactorySpi next = allDataStores.next();
all.add(next);
}
while (allDataAccess.hasNext()) {
all.add(allDataAccess.next());
}
return all.iterator();
}
static synchronized <T extends DataAccessFactory> Iterator<T> getAllDataStores(
FactoryRegistry registry, Class<T> category) {
return registry.getServiceProviders(category, null, null);
}
/**
* Finds all implemtaions of DataAccessFactory which have registered using
* the services mechanism, and that have the appropriate libraries on the
* classpath.
*
* @return An iterator over all discovered datastores which have registered
* factories, and whose available method returns true.
*/
public static synchronized Iterator<DataAccessFactory> getAvailableDataStores() {
FactoryRegistry serviceRegistry = getServiceRegistry();
Set<DataAccessFactory> availableDS = getAvailableDataStores(serviceRegistry,
DataAccessFactory.class);
Iterator<DataStoreFactorySpi> availableDataStores = DataStoreFinder
.getAvailableDataStores();
while (availableDataStores.hasNext()) {
availableDS.add(availableDataStores.next());
}
return availableDS.iterator();
}
static synchronized <T extends DataAccessFactory> Set<T> getAvailableDataStores(
FactoryRegistry registry, Class<T> targetClass) {
Set<T> availableDS = new HashSet<T>(5);
Iterator<T> it = registry.getServiceProviders(targetClass, null, null);
T dsFactory;
while (it.hasNext()) {
dsFactory = it.next();
if (dsFactory.isAvailable()) {
availableDS.add(dsFactory);
}
}
return availableDS;
}
/**
* Returns the service registry. The registry will be created the first time
* this method is invoked.
*/
private static FactoryRegistry getServiceRegistry() {
assert Thread.holdsLock(DataAccessFinder.class);
if (registry == null) {
registry = new FactoryCreator(Arrays.asList(new Class<?>[] { DataAccessFactory.class }));
}
return registry;
}
/**
* Scans for factory plug-ins on the application class path. This method is
* needed because the application class path can theoretically change, or
* additional plug-ins may become available. Rather than re-scanning the
* classpath on every invocation of the API, the class path is scanned
* automatically only on the first invocation. Clients can call this method
* to prompt a re-scan. Thus this method need only be invoked by
* sophisticated applications which dynamically make new plug-ins available
* at runtime.
*/
public static synchronized void scanForPlugins() {
DataStoreFinder.scanForPlugins();
getServiceRegistry().scanForPlugins();
}
/**
* Resets the factory finder and prepares for a new full scan of the SPI subsystems
*/
public static void reset() {
FactoryRegistry copy = registry;
registry = null;
if(copy != null) {
copy.deregisterAll();
}
}
}