private BoundCustomizer defaultParameterCustomizer(Parameter parameter, Integer i) {
        final Type parameterType = getParameterType(parameter);
        return new BoundCustomizer() {
            @Override
            public void warm(ConfigRegistry config) {
                create(config).warm(config);
            }

            @Override
            public void apply(SqlStatement<?> stmt, Object[] args) throws SQLException {
                create(stmt.getConfig()).apply(stmt, args[i]);
            }

            private SqlStatementParameterCustomizer create(ConfigRegistry config) {
                return getDefaultParameterCustomizerFactory(config)
                        .createForParameter(sqlObjectType, method, parameter, i, parameterType);
            }
        };
    }
Default parameter customizer for parameters with no annotations.
sqlobject/src/main/java/org/jdbi/v3/sqlobject/statement/internal/CustomizingStatementHandler.java