Mapping a row from a SQL data to a Java object

Question

I have a Java class with instance fields (and matching setter methods) that match the column names of a SQL database table. I would like to elegantly fetch a row from the table

Answer 1

When you execute a query you can get metadata from the ResultSet. You have access to the columns from this. Here's an example:

@RestController
public class MyController {

    @GetMapping("/characters")
    public List characters() {
        List results = new ArrayList<>();

        try (Connection conn = new Connection()) {
            conn.makeConnection();
            Statement stmt = conn.createStatement();

            ResultSet result = stmt.executeQuery("SELECT * FROM public.hello;");
            ResultSetMetaData resultMetaData = result.getMetaData();

            Set columns = new HashSet<>();

            for (int i = 1; i <= resultMetaData.getColumnCount(); i++) {
                columns.add(resultMetaData.getColumnName(i));
            }

            while (result.next()) {
                results.add(new Data(result, columns));
            }
        } catch (Exception e) {
            results.add(new Fail("404", e.getMessage()));
        }

        return results;
    }
}

public class Data implements Payload {
    private final Map data = new HashMap<>();

    public Data(ResultSet result, Set columns) throws SQLException {

        for (String column : columns) {
            data.put(column, result.getString(column));
        }
    }

    public Map getData() {
        return data;
    }
}

Now you can have one class object that parses out the columns and data for any table. You never really care what columns there are. The down side is that all of your info is now stored in a data field. So the payload would look something like:

[
  {"data":{"id":"1","name":"Rick Sanchez"}},
  {"data":{"id":"2","name":"Morty Smith"}},
  {"data":{"id":"3","message":"Summer Smith"}}
]