How to query for a List<String> in JdbcTemplate?

Question

I'm using Spring's JdbcTemplate and running a query like this:

SELECT COLNAME FROM TABLEA GROUP BY COLNAME 

There are no named parameters being passed, however, column name, COLNAME, will be passed by the user.

Questions

1. Is there a way to have placeholders, like ? for column names? For example SELECT ? FROM TABLEA GROUP BY ?

2. If I want to simply run the above query and get a List<String> what is the best way?

Currently I'm doing:

List<Map<String, Object>> data = getJdbcTemplate().queryForList(query); for (Map m : data) {   System.out.println(m.get("COLNAME")); } 

Answer 1

To populate a List of String, you need not use custom row mapper. Implement it using queryForList.

List<String>data=jdbcTemplate.queryForList(query,String.class) 

Answer 2

Is there a way to have placeholders, like ? for column names? For example SELECT ? FROM TABLEA GROUP BY ?

Use dynamic query as below:

String queryString = "SELECT "+ colName+ " FROM TABLEA GROUP BY "+ colName; 

If I want to simply run the above query and get a List what is the best way?

List<String> data = getJdbcTemplate().query(query, new RowMapper<String>(){                             public String mapRow(ResultSet rs, int rowNum)                                                           throws SQLException {                                     return rs.getString(1);                             }                        }); 

EDIT: To Stop SQL Injection, check for non word characters in the colName as :

          Pattern pattern = Pattern.compile("\\W");           if(pattern.matcher(str).find()){                //throw exception as invalid column name           }