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Can we convert a Java ResultSet/SqlRowSet from Database query directly to JSON array without Mapping it to a List<Type>?

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  Can we convert a Java ResultSet/SqlRowSet from Database query directly to JSON array without Mapping it to a List<Type>? kaushal patel <kpt1991@gmail.com> - 2015-05-22 01:21 -0700
    Re: Can we convert a Java ResultSet/SqlRowSet from Database query directly to JSON array without Mapping it to a List<Type>? Arne Vajhøj <arne@vajhoej.dk> - 2015-05-22 21:15 -0400

#31731 — Can we convert a Java ResultSet/SqlRowSet from Database query directly to JSON array without Mapping it to a List<Type>?

String sql = "select employee_id,first_name,last_name,email,salary from employees";

SqlRowSet  employees = null ;

try{
  employees = jdbcTemplate.queryForRowSet(sql);
}
catch(Exception e)
{
  e.printStackTrace();	
}
return employees ;

I want to know if there is any library present that can convert it to JSON.

I have tried with google GSON Library and Jackson Library but both requires first extraction of column to Type Class like Employee in this case.

If I am able to do this it can provide me a dynamic nature on my frontend like once we have 3 columns on frontend then we want 4 u just have to edit the query.

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#31733

On 5/22/2015 4:21 AM, kaushal patel wrote:
> String sql = "select employee_id,first_name,last_name,email,salary from employees";
>
> SqlRowSet  employees = null ;
>
> try{
>    employees = jdbcTemplate.queryForRowSet(sql);
> }
> catch(Exception e)
> {
>    e.printStackTrace();	
> }
> return employees ;
>
> I want to know if there is any library present that can convert it to JSON.
>
> I have tried with google GSON Library and Jackson Library but both requires first extraction of column to Type Class like Employee in this case.

It is not hard to code yourself.

Quick attempt:

	private static String quoteIfNeeded(Object o) {
		if(o instanceof String) {
			return "\"" + o.toString() + "\"";
		} else if(o instanceof Integer) {
			return o.toString();
		} else {
			throw new IllegalArgumentException(o.getClass().getName() + " not 
supported");
		}
	}
	public static String resultSet2JSON(ResultSet rs) throws SQLException {
		ArrayList<String> colnams = new ArrayList<>();
		ResultSetMetaData rsmd = rs.getMetaData();
		for(int i = 0; i < rsmd.getColumnCount(); i++) {
			colnams.add(rsmd.getColumnName(i + 1));
		}
		StringBuilder sb = new StringBuilder();
		sb.append("[");
		while(rs.next()) {
			sb.append("{");
			for(int i = 0; i < colnams.size(); i++) {
				if(i > 0) {
					sb.append(",");
				}
				sb.append(colnams.get(i));
				sb.append(":");
				Object o = rs.getObject(i + 1);
				sb.append(quoteIfNeeded(o));
			}
			sb.append("}");
		}
		sb.append("]");
		return sb.toString();
	}

Arne

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