Ошибка запроса к БД

Добрый день! Подскажите, пожалуйста, в чем ошибка:

Есть код, который подключается к БД и делает выборку:

private ArrayList<Book> getBooks(String str) {

    Statement stmt = null;
    ResultSet rs = null;
    Connection conn = null;

    try {
        conn = Database.getConnection();

        stmt = conn.createStatement();
        System.out.println(str);
        rs = stmt.executeQuery(str);
        while (rs.next()) {
            Book book = new Book();
            book.setId(rs.getLong("id"));
            book.setName(rs.getString("name"));
            book.setGenre(rs.getString("genre"));
            book.setIsbn(rs.getString("isbn"));
            book.setAuthor(rs.getString("author"));
            book.setPageCount(rs.getInt("page_count"));
            book.setPublishDate(rs.getInt("publish_year"));
            book.setPublisher(rs.getString("publisher"));
            book.setImage(rs.getBytes("image"));
            bookList.add(book);
        }

    } catch (SQLException ex) {
        Logger.getLogger(BookList.class.getName()).log(Level.SEVERE, null, ex);
   } finally {
        try {
            if (stmt != null) {
                stmt.close();
            }
            if (rs != null) {
                rs.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(BookList.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    System.out.println(bookList);
    return bookList;
}

public ArrayList<Book> getBooksByGenre(long id) {
    return getBooks("select b.id,b.name,b.isbn,b.page_count,b.publish_year, p.name as publisher, a.fio as author, g.name as genre, b.image from book b "
            + "inner join author a on b.author_id=a.id "
            + "inner join genre g on b.genre_id=g.id "
            + "inner join publisher p on b.publisher_id=p.id "
            + "where genre_id=" + id + " order by b.name "
            + "limit 0,5");

}

При выполнении получаю такие ошибки:

Severe:   java.sql.SQLException: Connection closed
at com.sun.gjc.spi.base.ConnectionHolder.checkValidity(ConnectionHolder.java:766)
at com.sun.gjc.spi.base.ConnectionHolder.createStatement(ConnectionHolder.java:254)
at com.sun.gjc.spi.jdbc40.ConnectionWrapper40.createStatement(ConnectionWrapper40.java:75)
at ru.web.beans.BookList.getBooks(BookList.java:27)
at ru.web.beans.BookList.getBooksByGenre(BookList.java:74)
at org.apache.jsp.pages.books_jsp._jspService(books_jsp.java:166)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:344)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:316)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:745)

В чём может быть проблема? Заранее большое спасибо!