org.geotools.data.DataAccessFinder Maven / Gradle / Ivy
Show all versions of gt-main Show documentation
/*
* 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 static java.util.stream.Collectors.toSet;
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.util.factory.FactoryCreator;
import org.geotools.util.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.
*
* In order to be located by this finder datasources must provide an implementation of the {@link
* DataAccessFactory} interface.
*
*
In addition to implementing this interface datasouces should have a services file:
* META-INF/services/org.geotools.data.DataAccessFactory
*
*
The file should contain a single line which gives the full name of the implementing class.
*
*
Example:
* org.geotools.data.mytype.MyTypeDataAccessFacotry
*/
public final class DataAccessFinder {
/** The logger for the filter module. */
protected static final Logger LOGGER =
org.geotools.util.logging.Logging.getLogger(DataAccessFinder.class);
/** The service registry for this manager. Will be initialized only when first needed. */
private static volatile 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.
*/
@SuppressWarnings("unchecked")
public static synchronized DataAccess getDataStore(
Map params) throws IOException {
Iterator ps = getAvailableDataStores();
return (DataAccess) getDataStore(params, ps);
}
static DataAccess getDataStore(
Map params, Iterator 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 getAllDataStores() {
Set all = new HashSet();
Iterator allDataStores = DataStoreFinder.getAllDataStores();
Iterator 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 Iterator getAllDataStores(
FactoryRegistry registry, Class category) {
return registry.getFactories(category, null, null).iterator();
}
/**
* 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 getAvailableDataStores() {
FactoryRegistry serviceRegistry = getServiceRegistry();
Set availableDS =
getAvailableDataStores(serviceRegistry, DataAccessFactory.class);
Iterator availableDataStores =
DataStoreFinder.getAvailableDataStores();
while (availableDataStores.hasNext()) {
availableDS.add(availableDataStores.next());
}
return availableDS.iterator();
}
static synchronized Set getAvailableDataStores(
FactoryRegistry registry, Class targetClass) {
return registry.getFactories(targetClass, null, null)
.filter(DataAccessFactory::isAvailable)
.collect(toSet());
}
/**
* 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();
}
}
}