Java and SQL : return null or throw exception?

Question

This is another debated subject, but this time i am searching only for the simple and documented answers. The scenario :

Let\'s assume the following method:

Answer 1

You can significantly reduce the amount of boilerplate JDBC code by using Spring-JDBC instead of plain-old JDBC. Here's the same method rewritten using Spring-JDBC

public static Hashtable getSomeDogs(String colName, String colValue) {

    StringBuffer sql = new StringBuffer();
    sql.append("SELECT * FROM ").append("dogs_table");
    sql.append(" WHERE ").append(colName).append("='");
    sql.append(colValue).append("'");

    Hashtable result = new Hashtable();

    RowMapper mapper = new RowMapper() {

        public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
            Dogs dog = new Dogs();
            //...initialize the dog from the current resultSet row
            result.put(new Long(dog.getId()), dog);
        }
    };
    (Hashtable) jdbcTemplate.queryForObject(sql, mapper);
}

Spring takes care of:

1. Iterating over the ResultSet
2. Closing the ResultSet
3. Handling exceptions consistently

As others have mentioned you really should use a PreparedStatement to construct the SQL instead of a String (or StringBuffer). If for some reason you can't do this, you could improve the readability of the query by constructing the SQL like this instead:

    String sql = 
        "SELECT * FROM dogs_table " +
        "WHERE " + "colName" + " = '" + colValue + "'";