dbunit 在系统应用(文件导入和导出)中的资源释放问题
我在应用中使用dbunit做文件的导入和导出功能，现在导入和导出功能都能很好的实现，但是有一个资源释放的问题，一直都没找着原因，现把代码贴出来，望同志们发表高见。

public abstract class BaseImportor extends AbstractStep implements Importor {    private final static Log log = LogFactory.getLog(BaseImportor.class);        private static final String batchID = "http://www.dbunit.org/features/batchedStatements";    private static DataSource ds;        protected IDataSet srcDataSet;    protected String _type = TYPE_CLEAN_INSERT;    private boolean _transaction = false;    private DatabaseOperation _operation;    protected boolean _forwardOperation = true;        /**     * 通过spring注射dataSource     * @param dataSource     */    public final void setDataSource(final DataSource dataSource){    ds = dataSource;    }    public BaseImportor() {            }    /**     * 获取连接     * @return     * @throws DatabaseUnitException     */    protected IDatabaseConnection getConnection() throws DatabaseUnitException{    IDatabaseConnection iDataBaseConnection = null;try {String schema = ds.getConnection().getMetaData().getUserName();iDataBaseConnection = new DatabaseConnection(ds.getConnection(), schema);DatabaseConfig config = iDataBaseConnection.getConfig();if (!config.getFeature(batchID)) {    config.setFeature(batchID, true);}log.debug("get database connection with schema '"+schema+"'");} catch (SQLException e) {log.error(e);throw new DatabaseUnitException(e);}        return iDataBaseConnection;    }    public String getType()    {        return _type;    }    public DatabaseOperation getDbOperation()    {        return _operation;    }    public boolean isTransaction()    {        return _transaction;    }    /**     * 设置操作类型     */    public void setType(String type)    {        if (TYPE_UPDATE.equals(type))        {            _operation = DatabaseOperation.UPDATE;            _forwardOperation = true;        }        else if (TYPE_INSERT.equals(type))        {            _operation = DatabaseOperation.INSERT;            _forwardOperation = true;        }        else if (TYPE_REFRESH.equals(type))        {            _operation = DatabaseOperation.REFRESH;            _forwardOperation = true;        }        else if (TYPE_DELETE.equals(type))        {            _operation = DatabaseOperation.DELETE;            _forwardOperation = false;        }        else if (TYPE_DELETE_ALL.equals(type))        {            _operation = DatabaseOperation.DELETE_ALL;            _forwardOperation = false;        }        else if (TYPE_CLEAN_INSERT.equals(type))        {            _operation = DatabaseOperation.CLEAN_INSERT;            _forwardOperation = false;        }        else if (TYPE_NONE.equals(type))        {            _operation = DatabaseOperation.NONE;            _forwardOperation = true;        }        else if (TYPE_MSSQL_CLEAN_INSERT.equals(type))        {            _operation = InsertIdentityOperation.CLEAN_INSERT;            _forwardOperation = false;        }        else if (TYPE_MSSQL_INSERT.equals(type))        {            _operation = InsertIdentityOperation.INSERT;            _forwardOperation = true;        }        else if (TYPE_MSSQL_REFRESH.equals(type))        {            _operation = InsertIdentityOperation.REFRESH;            _forwardOperation = true;        }        else        {            throw new IllegalArgumentException("Type must be one of: UPDATE, INSERT,"                    + " REFRESH, DELETE, DELETE_ALL, CLEAN_INSERT, MSSQL_INSERT, "                    + " or MSSQL_REFRESH but was: " + type);        }        _type = type;    }    public void setTransaction(boolean transaction)    {        _transaction = transaction;    }    public void execute(IDatabaseConnection connection) throws DatabaseUnitException    {        if (_operation == null)        {            throw new DatabaseUnitException("Inputor.execute(): setType(String) must be called before execute()!");        }        if (_operation == DatabaseOperation.NONE)        {            return;        }        try        {        DatabaseOperation operation = (_transaction ? new TransactionOperation(_operation) : _operation);            operation.execute(connection, getSrcDataSet());        }        catch (SQLException e)        {            throw new DatabaseUnitException(e);        }finally{try {connection.close();} catch (Exception e) {}finally{connection = null;}//显示关闭连接}    }    public String getLogMessage()    {        return "";    }        public abstract IDataSet getSrcDataSet();    }

public class ExcelImportor extends BaseImportor{/** * Logger for this class */private static final Logger logger = Logger.getLogger(ExcelImportor.class);private InputStream inputStream;/* （非 Javadoc） * @see com.harmony.ioput.BaseInputor#getSrcDataSet() */@Overridepublic IDataSet getSrcDataSet(){// TODOIDataSet dataSet = null;try {if(inputStream != null){dataSet = new XlsDataSet(inputStream);}else{throw new IllegalArgumentException("请在file和inputStream中选择一种数据源");}} catch (DataSetException e) {logger.error(e);throw new DatabaseUnitRuntimeException(e);} catch (IOException e) {logger.error(e);throw new RuntimeException(e);}finally{try{//释放资源inputStream.close();}catch(Exception e){}finally{inputStream = null;}}return dataSet;}/* （非 Javadoc） * @see com.harmony.ioput.Inputor#setFile(java.io.File) */public void setFile(File src) {try {this.inputStream = new FileInputStream(src);} catch (FileNotFoundException e) {throw new IllegalArgumentException(e);}}/* （非 Javadoc） * @see com.harmony.ioput.Inputor#setInputStream(java.io.InputStream) */public void setInputStream(InputStream in) {this.inputStream = in;}/** * @return inputStream */public InputStream getInputStream() {return inputStream;}/** * 执行导入操作 */public void execute() {try {super.execute(getConnection());} catch (DatabaseUnitException e) {logger.error(e);throw new DatabaseUnitRuntimeException(e);}}}

在代码中，我都有显示的释放connection和关闭inputstrean，但是为什么程序运行到第8次的时候不再运行了，就像是死锁了。
protected IDatabaseConnection getConnection() throws DatabaseUnitException{ IDatabaseConnection iDataBaseConnection = null;try {Connection _connection = ds.getConnection();String schema = _connection.getMetaData().getUserName();iDataBaseConnection = new DatabaseConnection(_connection, schema);DatabaseConfig config = iDataBaseConnection.getConfig();if (!config.getFeature(batchID)) { config.setFeature(batchID, true);}log.debug("get database connection with schema '"+schema+"'");} catch (SQLException e) {log.error(e);throw new DatabaseUnitException(e);} return iDataBaseConnection; }