Open CSV to export resultset to string type

Question

I want to export the result set of the SQL query to a CSV file. I am using opencsv to export to CSV file. I am using below code to achieve it.

ResultSet rs = statement.executeQuery(queryString);
CSVWriter writer = new CSVWriter(new fileWriter "testFile.csv"), '|',CSVWriter.NO_QUOTE_CHARACTER);
writer.writeAll(rs, true);

But the problem I face is, it automatically exports to the datatype of the database column which is from resultset.

Example: if I a column with datatype as float in datatype in CSV file I see as 100.00 and for another column I see value as 2.041928E+8 for 204192800.

But I want to CSV file to export to string type. The value as it as in the database.

How can I export the resulttype to CSV file with string datatype using opencsv?

Answer 1

And Another solution is, create your custom ResultSet Wrapper with your real resultset (source) and call

Also, you can create your custom ResultSetMetaData Wrapper to response ColumnType has String.

    writer.writeAll(new MyResultSet(rs), true);

//Wrapper class

public class MyResultSet implements Resultset{

 public MyResultSet(Resultset source, Map<String, NumberFormat > formatters){
//setting constructor properties and you can read here SQL resultset Metadata to complete    formatters
}

 //.... you will implement all sql.Resultset methods

  //example to implements

 public String getString(String columnName){
    return formatters.get(columnName).format(source.getInt(columnName));
  }

 public ResultSetMetaData getMetaData(){
   return new MyResultSetMetaData(source);
 }

} 

}
//
   public MyResultSetMetaData implements ResultSetMetaData{
 //will implement all ResultSetMetaData methods,

   //replace Numeric to String the column Type, then the value has retrieved by getString(column)
       public int getColumnType(int columnIndex){
  return Types.VARCHAR;

}

}

Answer 2

You can create your SQl has String example,

example with oracle:

  select num||'',to_char(num2) from xxx 

or use Sql number formatter, and the resultset response with String value and not Number Values.

Answer 3

I think that the best way is

writer.setResultService(new MyResultSetSevice());
writer.writeAll(rs, true);

and create a class

  //http://opencsv.sourceforge.net/apidocs/index.html?au/com/bytecode/opencsv/CSVWriter.html
  public class MyResultSetSevice implements ResultSetHelper{


  public String[] getColumnValues(ResultSet rs) 
  {
      return formattedColumnValues;
  }

  String[]  getColumnValues(ResultSet rs, boolean trim) {
   return formattedColumnValues;

  }
}

Answer 4

Another option is to explicitly write each line. It's a fairly simple method and has the advantage that you can use the "applyQuotesToAll" parameter to get CSVWriter to only quote values which need quotes, rather than everything or nothing.

public static void toCSV(ResultSet rs, OutputStream os)
        throws SQLException, IOException {
    CSVWriter csvWriter = new CSVWriter(new OutputStreamWriter(os));

    ResultSetMetaData metadata = rs.getMetaData();
    int columnCount = metadata.getColumnCount();
    String[] column = new String[columnCount];
    for (int i = 1; i <= columnCount; i++) {
        column[i-1] = metadata.getColumnName(i);
    }
    csvWriter.writeNext(column, false);

    while (rs.next()) {
        for (int i = 1; i <= columnCount; i++) {
            column[i-1] = rs.getString(i);
        }
        csvWriter.writeNext(column, false);
    }

    csvWriter.close();
}