PollingJdbcDriverManager.java

package org.springframework.roo.addon.jdbc.polling.internal;

import java.sql.Driver;
import java.util.HashSet;
import java.util.Set;
import java.util.logging.Logger;

import org.apache.commons.lang3.Validate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.ReferencePolicy;
import org.apache.felix.scr.annotations.ReferenceStrategy;
import org.apache.felix.scr.annotations.Service;
import org.springframework.roo.addon.jdbc.JdbcDriverManager;
import org.springframework.roo.addon.jdbc.polling.JdbcDriverProvider;
import org.springframework.roo.support.api.AddOnSearch;
import org.springframework.roo.support.api.AddOnSearch.SearchType;
import org.springframework.roo.support.logging.HandlerUtils;

/**
 * Polls all OSGi-located {@link JdbcDriverProvider} instances and returns the
 * first JDBC driver provided by an instance.
 * <p>
 * Failing the location of a suitable {@link JdbcDriverProvider}, automatically
 * suggests an add-on which may be able to provide the driver as a console
 * message.
 * 
 * @author Alan Stewart
 * @author Ben Alex
 * @since 1.1
 */
@Component
@Service
@Reference(name = "jdbcDriverProvider", strategy = ReferenceStrategy.EVENT,
    policy = ReferencePolicy.DYNAMIC, referenceInterface = JdbcDriverProvider.class,
    cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE)
public class PollingJdbcDriverManager implements JdbcDriverManager {

  private static final Logger LOGGER = HandlerUtils.getLogger(PollingJdbcDriverManager.class);

  @Reference
  private AddOnSearch addOnSearch;
  private final Set<JdbcDriverProvider> providers = new HashSet<JdbcDriverProvider>();

  protected void bindJdbcDriverProvider(final JdbcDriverProvider listener) {
    synchronized (providers) {
      providers.add(listener);
    }
  }

  public Driver loadDriver(final String driverClassName, final boolean displayAddOns)
      throws RuntimeException {
    Validate.notBlank(driverClassName, "Driver class name required");
    synchronized (providers) {
      for (final JdbcDriverProvider provider : providers) {
        final Driver driver = provider.loadDriver(driverClassName);
        if (driver != null) {
          return driver;
        }
      }

      if (!displayAddOns) {
        // Caller requested add-on information not be displayed (might
        // be in a TAB assist section etc)
        return null;
      }

      // No implementation could provide it

      // Do a silent (console message free) lookup of matches
      final Integer matches = addOnSearch.searchAddOns(driverClassName, SearchType.JDBCDRIVER);

      // Render to screen if required
      if (matches == null) {
        LOGGER.info("Spring Roo automatic add-on discovery service currently unavailable");
      } else if (matches > 0) {
        LOGGER.info("Located add-on" + (matches == 1 ? "" : "s")
            + " that may offer this JDBC driver");
      }

      return null;
    }
  }

  protected void unbindJdbcDriverProvider(final JdbcDriverProvider listener) {
    synchronized (providers) {
      providers.remove(listener);
    }
  }
}