Changeset: 5ea126405bac for monetdb-java
URL: https://dev.monetdb.org/hg/monetdb-java?cmd=changeset;node=5ea126405bac
Modified Files:
example/MJDBCTest.java
example/PreparedExample.java
example/SQLImport.java
example/SQLcopyinto.java
Branch: default
Log Message:
Update java examples code
diffs (153 lines):
diff --git a/example/MJDBCTest.java b/example/MJDBCTest.java
--- a/example/MJDBCTest.java
+++ b/example/MJDBCTest.java
@@ -17,15 +17,24 @@ import java.sql.*;
*/
public class MJDBCTest {
public static void main(String[] args) throws Exception {
- // make sure the driver is loaded
- Class.forName("nl.cwi.monetdb.jdbc.MonetDriver");
- // turn on debugging (disabled)
- //nl.cwi.monetdb.jdbc.MonetConnection.setDebug(true);
- Connection con =
DriverManager.getConnection("jdbc:monetdb://localhost/notused", "monetdb",
"monetdb");
+ String MonetDB_JDBC_URL =
"jdbc:monetdb://localhost:50000/demo"; // change host, port and
databasename
+ Connection con;
+ try {
+ con = DriverManager.getConnection(MonetDB_JDBC_URL,
"monetdb", "monetdb");
+ } catch (SQLException e) {
+ System.err.println("Failed to connect to MonetDB
server! Message: " + e.getMessage());
+ }
+
+ if (con == null) {
+ System.err.println("Failed to create a connection
object!");
+ return;
+ }
+
Statement st = con.createStatement();
ResultSet rs;
- rs = st.executeQuery("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;");
+ 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;";
+ rs = st.executeQuery(sql);
// get meta data and print columns with their type
ResultSetMetaData md = rs.getMetaData();
for (int i = 1; i <= md.getColumnCount(); i++) {
@@ -49,39 +58,51 @@ public class MJDBCTest {
// we ask the database for 22 rows, while we set the JDBC
driver to
// 5 rows, this shouldn't be a problem at all...
rs = st.executeQuery("select * from a limit 22");
+ int var1_cnr = rs.findColumn("var1");
+ int var2_cnr = rs.findColumn("var2");
+ int var3_cnr = rs.findColumn("var3");
+ int var4_cnr = rs.findColumn("var4");
// read till the driver says there are no rows left
for (int i = 0; rs.next(); i++) {
- System.out.print("[" + rs.getString("var1") + "]");
- System.out.print("[" + rs.getString("var2") + "]");
- System.out.print("[" + rs.getInt("var3") + "]");
- System.out.println("[" + rs.getString("var4") + "]");
+ System.out.println(
+ "[" + rs.getString(var1_cnr) + "]" +
+ "[" + rs.getString(var2_cnr) + "]" +
+ "[" + rs.getInt(var3_cnr) + "]" +
+ "[" + rs.getString(var4_cnr) + "]" );
}
-
- // this close is not needed, should be done by next
execute(Query) call
+
+ // this rs.close is not needed, should be done by next
execute(Query) call
// however if there can be some time between this point and the
next
// execute call, it is from a resource perspective better to
close it.
- //rs.close();
+ rs.close();
// unset the row limit; 0 means as much as the database sends us
st.setMaxRows(0);
// we only ask 10 rows
rs = st.executeQuery("select * from b limit 10;");
+ int rowid_cnr = rs.findColumn("rowid");
+ int id_cnr = rs.findColumn("id");
+ var1_cnr = rs.findColumn("var1");
+ var2_cnr = rs.findColumn("var2");
+ var3_cnr = rs.findColumn("var3");
+ var4_cnr = rs.findColumn("var4");
// and simply print them
while (rs.next()) {
- System.out.print(rs.getInt("rowid") + ", ");
- System.out.print(rs.getString("id") + ", ");
- System.out.print(rs.getInt("var1") + ", ");
- System.out.print(rs.getInt("var2") + ", ");
- System.out.print(rs.getString("var3") + ", ");
- System.out.println(rs.getString("var4"));
+ System.out.println(
+ rs.getInt(rowid_cnr) + ", " +
+ rs.getString(id_cnr) + ", " +
+ rs.getInt(var1_cnr) + ", " +
+ rs.getInt(var2_cnr) + ", " +
+ rs.getString(var3_cnr) + ", " +
+ rs.getString(var4_cnr) );
}
- // this close is not needed, as the Statement will close the
last
+ // 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();
+ rs.close();
// perform a ResultSet-less query (with no trailing ; since
that should
// be possible as well and is JDBC standard)
@@ -90,12 +111,12 @@ public class MJDBCTest {
// support returning the affected rows.
st.executeUpdate("delete from a where var1 = 'zzzz'");
- // closing the connection should take care of closing all
generated
- // statements from it...
// 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();
+ st.close();
+ // closing the connection should take care of closing all
generated
+ // statements from it...
con.close();
}
}
diff --git a/example/PreparedExample.java b/example/PreparedExample.java
--- a/example/PreparedExample.java
+++ b/example/PreparedExample.java
@@ -15,8 +15,6 @@ import java.sql.*;
*/
public class PreparedExample {
public static void main(String[] args) throws Exception {
- // make sure the driver is loaded
- Class.forName("nl.cwi.monetdb.jdbc.MonetDriver");
Connection con =
DriverManager.getConnection("jdbc:monetdb://localhost/notused", "monetdb",
"monetdb");
PreparedStatement st = con.prepareStatement("SELECT ? AS a1, ?
AS a2");
ResultSet rs;
diff --git a/example/SQLImport.java b/example/SQLImport.java
--- a/example/SQLImport.java
+++ b/example/SQLImport.java
@@ -37,8 +37,6 @@ public class SQLImport {
// open the file
BufferedReader fr = new BufferedReader(new FileReader(args[0]));
- // make sure the driver is loaded
- Class.forName("nl.cwi.monetdb.jdbc.MonetDriver");
// request a connection suitable for Monet from the driver
manager
// note that the database specifier is currently not
implemented, for
// Monet itself can't access multiple databases.
diff --git a/example/SQLcopyinto.java b/example/SQLcopyinto.java
--- a/example/SQLcopyinto.java
+++ b/example/SQLcopyinto.java
@@ -22,8 +22,6 @@ import nl.cwi.monetdb.mcl.io.*;
public class SQLcopyinto {
public static void main(String[] args) throws Exception {
- // make sure the driver is loaded
- Class.forName("nl.cwi.monetdb.jdbc.MonetDriver");
// request a connection suitable for Monet from the driver
manager
// note that the database specifier is currently not
implemented, for
// Monet itself can't access multiple databases.
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