I am using CsvJdbc (it is a JDBC-driver for csv-files) to access a csv-file. I don't know how many columns the csv-file contains. How can I get the number of columns? Is there any JDBC-function for this? I can not find any methods for this in java.sql.ResultSet.
For accessing the file, I use code similar to the example on the CsvJdbc website.
PreparedStatement ps=con.prepareStatement("select * from stud");
ResultSet rs=ps.executeQuery();
ResultSetMetaData rsmd=rs.getMetaData();
System.out.println("columns: "+rsmd.getColumnCount());
System.out.println("Column Name of 1st column: "+rsmd.getColumnName(1));
System.out.println("Column Type Name of 1st column: "+rsmd.getColumnTypeName(1));
This will print the data in columns and comes to new line once last column is reached.
ResultSetMetaData resultSetMetaData = res.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
for(int i =1; i<=columnCount; i++){
if(!(i==columnCount)){
System.out.print(res.getString(i)+"\t");
}
else{
System.out.println(res.getString(i));
}
}
Number of a columns in the result set you can get with code (as DB is used PostgreSQL):
//load the driver for PostgreSQL Class.forName("org.postgresql.Driver"); String url = "jdbc:postgresql://localhost/test"; Properties props = new Properties(); props.setProperty("user","mydbuser"); props.setProperty("password","mydbpass"); Connection conn = DriverManager.getConnection(url, props); //create statement Statement stat = conn.createStatement(); //obtain a result set ResultSet rs = stat.executeQuery("SELECT c1, c2, c3, c4, c5 FROM MY_TABLE"); //from result set give metadata ResultSetMetaData rsmd = rs.getMetaData(); //columns count from metadata object int numOfCols = rsmd.getColumnCount();
But you can get more meta-informations about columns:
for(int i = 1; i <= numOfCols; i++)
{
System.out.println(rsmd.getColumnName(i));
}
And at least but not least, you can get some info not just about table but about DB too, how to do it you can find here and here.
After establising the connection and executing the query try this:
ResultSet resultSet;
int columnCount = resultSet.getMetaData().getColumnCount();
System.out.println("column count : "+columnCount);
Source: Stackoverflow.com