+
−/*
+
− * SPDX-License-Identifier: MPL-2.0
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− *
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− * This Source Code Form is subject to the terms of the Mozilla Public
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− * License, v. 2.0.  If a copy of the MPL was not distributed with this
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− * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
− *
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− * Copyright 2024, 2025 MonetDB Foundation;
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− * Copyright August 2008 - 2023 MonetDB B.V.;
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− * Copyright 1997 - July 2008 CWI.
+
− */
+
−
+
−import java.sql.*;
+
−
+
−/**
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− * This example assumes there exists tables a and b filled with some data.
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− * On these tables some queries are executed and the JDBC driver is tested
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− * on it's accuracy and robustness against 'users'.
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− *
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− * @author Fabian Groffen
+
− */
+
−public class MJDBCTest {
+
−	public static void main(String[] args) throws Exception {
+
−		String MonetDB_JDBC_URL = "jdbc:monetdb://localhost:50000/demo";	// change host, port and databasename
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−		Connection con = null;
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−		try {
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−			con = DriverManager.getConnection(MonetDB_JDBC_URL, "monetdb", "monetdb");
+
−		} catch (SQLException e) {
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−			System.err.println("Failed to connect to MonetDB server! Message: " + e.getMessage());
+
−		}
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−
+
−		if (con == null) {
+
−			System.err.println("Failed to create a connection object!");
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−			return;
+
−		}
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−
+
−		Statement st = con.createStatement();
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−		ResultSet rs;
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−
+
−		String sql = "SELECT a.var1, COUNT(b.id) as total FROM a, b WHERE a.var1 = b.id AND a.var1 = 'andb' GROUP BY a.var1 ORDER BY a.var1, total;";
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−		rs = st.executeQuery(sql);
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−		// get meta data and print columns with their type
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−		ResultSetMetaData md = rs.getMetaData();
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−		for (int i = 1; i <= md.getColumnCount(); i++) {
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−			System.out.print(md.getColumnName(i) + ":" +
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−				md.getColumnTypeName(i) + "\t");
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−		}
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−		System.out.println("");
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−		// print the data: only the first 5 rows, while there probably are
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−		// a lot more. This shouldn't cause any problems afterwards since the
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−		// result should get properly discarded on the next query
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−		for (int i = 0; rs.next() && i < 5; i++) {
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−			for (int j = 1; j <= md.getColumnCount(); j++) {
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−				System.out.print(rs.getString(j) + "\t");
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−			}
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−			System.out.println("");
+
−		}
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−		
+
−		// tell the driver to only return 5 rows, it can optimize on this
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−		// value, and will not fetch any more than 5 rows.
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−		st.setMaxRows(5);
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−		// we ask the database for 22 rows, while we set the JDBC driver to
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−		// 5 rows, this shouldn't be a problem at all...
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−		rs = st.executeQuery("select * from a limit 22");
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−		int var1_cnr = rs.findColumn("var1");
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−		int var2_cnr = rs.findColumn("var2");
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−		int var3_cnr = rs.findColumn("var3");
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−		int var4_cnr = rs.findColumn("var4");
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−		// read till the driver says there are no rows left
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−		for (int i = 0; rs.next(); i++) {
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−			System.out.println(
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−				"[" + rs.getString(var1_cnr) + "]" +
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−				"[" + rs.getString(var2_cnr) + "]" +
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−				"[" + rs.getInt(var3_cnr) + "]" +
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−				"[" + rs.getString(var4_cnr) + "]" );
+
−		}
+
−
+
−		// this rs.close is not needed, should be done by next execute(Query) call
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−		// however if there can be some time between this point and the next
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−		// execute call, it is from a resource perspective better to close it.
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−		rs.close();
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−		
+
−		// unset the row limit; 0 means as much as the database sends us
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−		st.setMaxRows(0);
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−		// we only ask 10 rows
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−		rs = st.executeQuery("select * from b limit 10;");
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−		int rowid_cnr = rs.findColumn("rowid");
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−		int id_cnr = rs.findColumn("id");
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−		var1_cnr = rs.findColumn("var1");
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−		var2_cnr = rs.findColumn("var2");
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−		var3_cnr = rs.findColumn("var3");
+
−		var4_cnr = rs.findColumn("var4");
+
−		// and simply print them
+
−		while (rs.next()) {
+
−			System.out.println(
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−				rs.getInt(rowid_cnr) + ", " +
+
−				rs.getString(id_cnr) + ", " +
+
−				rs.getInt(var1_cnr) + ", " +
+
−				rs.getInt(var2_cnr) + ", " +
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−				rs.getString(var3_cnr) + ", " +
+
−				rs.getString(var4_cnr) );
+
−		}
+
−		
+
−		// this close is not required, as the Statement will close the last
+
−		// ResultSet around when it's closed
+
−		// again, if that can take some time, it's nicer to close immediately
+
−		// the reason why these closes are commented out here, is to test if
+
−		// the driver really cleans up it's mess like it should
+
−		rs.close();
+
−
+
−		// perform a ResultSet-less query (with no trailing ; since that should
+
−		// be possible as well and is JDBC standard)
+
−		// Note that this method should return the number of updated rows. This
+
−		// method however always returns -1, since Monet currently doesn't
+
−		// support returning the affected rows.
+
−		st.executeUpdate("delete from a where var1 = 'zzzz'");
+
−
+
−		// Don't forget to do it yourself if the connection is reused or much
+
−		// longer alive, since the Statement object contains a lot of things
+
−		// you probably want to reclaim if you don't need them anymore.
+
−		st.close();
+
−		// closing the connection should take care of closing all generated
+
−		// statements from it...
+
−		con.close();
+
−	}
+
−}