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copied!<p>Your best bet is to <strong>not</strong> store the data in Java's memory in any way, but just write the obtained data to the response <strong>immediately</strong> as the data comes in. You also need to configure the MySQL JDBC driver to serve the resultset row-by-row by <a href="http://java.sun.com/javase/6/docs/api/java/sql/Statement.html#setFetchSize%28int%29" rel="noreferrer"><code>Statement#setFetchSize()</code></a> as per the <a href="http://dev.mysql.com/doc/refman/5.0/en/connector-j-reference-implementation-notes.html" rel="noreferrer">MySQL JDBC driver documentation</a>, otherwise it will cache the whole thing in memory.</p> <p>Assuming you're familiar with Servlets, here's a kickoff example which takes that all into account:</p> <pre><code>protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/plain"); response.setHeader("Content-Disposition", "attachment;filename=numbers.txt"); // Force download popup. Connection connection = null; Statement statement = null; ResultSet resultSet = null; Writer writer = response.getWriter(); try { connection = database.getConnection(); statement = connection.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY); statement.setFetchSize(Integer.MIN_VALUE); resultSet = statement.executeQuery("SELECT number FROM phonenumbers"); while (resultSet.next()) { writer.write(resultSet.getString("number")); if (!resultSet.isLast()) { writer.write(","); } } } catch (SQLException e) { throw new ServletException("Query failed!", e); } finally { if (resultSet != null) try { resultSet.close; } catch (SQLException logOrIgnore) {} if (statement != null) try { statement.close; } catch (SQLException logOrIgnore) {} if (connection != null) try { connection.close; } catch (SQLException logOrIgnore) {} } } </code></pre>

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