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The JDBC API offers no built-in object mapping mechanism. In order to use high level types of your domain, use a converter to map results to your types. Converters are just plain Java classes that have at least one method that converts a java.sql.ResultSet into some other type. Each converter has an alias to make it easier to reference different converters without specifying their fully qualified name.

Map Converter

In case you do not want to use custom domain types, YoSQL provides a built-in default converter that returns a Map<String, Object>. That converter is declared as the defaultConverter if not otherwise specified by yourself, thus newly generated code will always return Maps at first. You can disable generating the mapping converter by using generateMapConverter. You can change its location with mapConverterClass, its method name with mapConverterMethod and its alias with mapConverterAlias. Methods that use the mapping converter have a signature similar to this:

Optional<Map<String, Object>> someMethod()
List<Map<String, Object>> someMethod()
Stream<Map<String, Object>> someMethod()

Default Converter

If not otherwise specified, generated code will use the default converter to converter between java.sql.ResultSet and some type declared by the configured default converter. In case you want to adjust the converter used by all your statements, set the defaultConverter configuration option accordingly. By default, this points to the map converter mentioned above.

Custom Converter

In order to use your own domain types in generated code, write a custom converter like in the following example and register each custom converter using the rowConverters configuration option:

package my.own;

import java.sql.ResultSet;
import java.sql.SQLException;

import my.own.User;
import my.own.persistence.util.ResultState;

public class UserConverter {

    public User apply(ResultState result) throws SQLException {
        ResultSet resultSet = result.getResultSet();
        User pojo = new User();
        return pojo;


You can choose package, class name and method name at will. The converter method gives you full control about how you want to handle ResultSets. You can use your own converter either by specifying it as the default converter mentioned above or by declaring it as a resultRowConverter with either its fully qualified name or its alias like this in the front matter of your SQL statements:

-- resultRowConverter: my.own.UserConverter
FROM    users

Generated code will now use your custom converter along with the result type configured for your converter, e.g.:

Optional<User> someMethod()
List<User> someMethod()
Stream<User> someMethod()

Tip: In case you want to use custom types, but do not want to write your own converter, consider using SimpleFlatMapper with its built-in support for JDBC ResultSets.