Description:
ResultSetMetaData.getColumnName() function sometimes returns null instead of the proper column name.
from my experience, it returns null when querying from dual and using count() funciton in select statement.
How to repeat:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
public class Test{
public static void main(String[] args) throws Exception{
Class.forName("com.mysql.jdbc.Driver").newInstance();
// adjust parameter
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/test?user=root&password=root");
ResultSet rs = null;
PreparedStatement ps = null;
try{
ps = conn.prepareStatement("SELECT to_days('2006-10-15') day FROM dual");
rs = ps.executeQuery();
// get result details
ResultSetMetaData rsmd = rs.getMetaData();
int numColumns = rsmd.getColumnCount();
String[] columnNames = new String[numColumns];
for (int i=0;i<numColumns;i++){
columnNames[i] = rsmd.getColumnName(i+1);
System.out.println("column name: " + rsmd.getColumnName(i+1));
}
}finally {
if (rs != null) {
try {rs.close();}
catch (SQLException sqlEx) {}
rs = null;
}
if (ps != null) {
try {ps.close();}
catch (SQLException sqlEx) {}
ps = null;
}
conn.close();
}
}
}
Suggested fix:
ResultSetMetaData.getColumnName() should still return the column name regardless of what table is queried.
Description: ResultSetMetaData.getColumnName() function sometimes returns null instead of the proper column name. from my experience, it returns null when querying from dual and using count() funciton in select statement. How to repeat: import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; public class Test{ public static void main(String[] args) throws Exception{ Class.forName("com.mysql.jdbc.Driver").newInstance(); // adjust parameter Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/test?user=root&password=root"); ResultSet rs = null; PreparedStatement ps = null; try{ ps = conn.prepareStatement("SELECT to_days('2006-10-15') day FROM dual"); rs = ps.executeQuery(); // get result details ResultSetMetaData rsmd = rs.getMetaData(); int numColumns = rsmd.getColumnCount(); String[] columnNames = new String[numColumns]; for (int i=0;i<numColumns;i++){ columnNames[i] = rsmd.getColumnName(i+1); System.out.println("column name: " + rsmd.getColumnName(i+1)); } }finally { if (rs != null) { try {rs.close();} catch (SQLException sqlEx) {} rs = null; } if (ps != null) { try {ps.close();} catch (SQLException sqlEx) {} ps = null; } conn.close(); } } } Suggested fix: ResultSetMetaData.getColumnName() should still return the column name regardless of what table is queried.