source: ether_2012/persistence/interface/com/ether/PersistenceHelper.java @ 319

package com.ether;

import java.util.Collection;
import com.ether.PersistenceException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.dao.CleanupFailureDataAccessException;
import org.springframework.dao.DataAccessException;

public final class PersistenceHelper
{
    /**
     * Returns an unique result from a collection of results.
     * 
     * @throws PersistenceException : if more than one result is contained in the collection an exception is thrown.
     */
    public static <O> O uniqueResult(final Collection<O> results)
            throws PersistenceException
    {
        if (results == null || results.isEmpty())
            return null;
        else if (results.size() > 1)
            throw new PersistenceException(PersistenceException.PersistenceCode.INVALID_API_USAGE, "unique result expected !");
        else
            return results.iterator().next();
    }

    public static <O> O firstResult(final Collection<O> results)
    {
        if (results == null || results.isEmpty()) return null;
        return results.iterator().next();
    }
  
    /**
     * Converts an exception to a DAO exception.
     * 
     * @param exception : the exception.
     * @return the DAO exception.
     */
    public static PersistenceException convert(final Exception exception)
    {
        // Propagates the exception if exception is persistence exception
        if (exception instanceof PersistenceException)
            return (PersistenceException) exception;

        // Rewraps exception if data access exception
        final PersistenceException.PersistenceCode code;

        if (exception instanceof DataAccessException)
        {
            if (exception instanceof CleanupFailureDataAccessException)
            {
                code = PersistenceException.PersistenceCode.CLEANUP_FAILURE;
            }
            else if (exception instanceof org.springframework.dao.ConcurrencyFailureException)
            {
                code = PersistenceException.PersistenceCode.CONCURRENCY_FAILURE;
            }
            else if (exception instanceof org.springframework.dao.DataAccessResourceFailureException)
            {
                code = PersistenceException.PersistenceCode.RESOURCE_FAILURE;
            }
            else if (exception instanceof org.springframework.dao.DataIntegrityViolationException)
            {
                code = PersistenceException.PersistenceCode.INTEGRITY_VIOLATION;
            }
            else if (exception instanceof org.springframework.dao.DataRetrievalFailureException)
            {
                code = PersistenceException.PersistenceCode.RETRIEVAL_FAILURE;
            }
            else if (exception instanceof org.springframework.jdbc.datasource.lookup.DataSourceLookupFailureException)
            {
                code = PersistenceException.PersistenceCode.DATA_SOURCE_LOOKUP_FAILURE;
            }
            else if (exception instanceof org.springframework.dao.InvalidDataAccessApiUsageException)
            {
                code = PersistenceException.PersistenceCode.INVALID_API_USAGE;
            }
            else if (exception instanceof org.springframework.dao.PermissionDeniedDataAccessException)
            {
                code = PersistenceException.PersistenceCode.PERMISSION_DENIED;
            }
            else
            {
                code = PersistenceException.PersistenceCode.UNKNOWN_FAILURE;
            }
        }
        else
        {
            code = PersistenceException.PersistenceCode.UNKNOWN_FAILURE;
        }

        final StringBuilder message = new StringBuilder();
        message.append(exception.getMessage());

        final Throwable cause = exception.getCause();
        if (null != cause)
        {
            message.append(" : ").append(cause.getMessage());
        }

        return new PersistenceException(code, message.toString(),
                exception);
    }

    private static final Log LOGGER = LogFactory.getLog(PersistenceHelper.class);
}