Simple Object type here means a Java data type that is supported directly by JDBC, excepting only user-defined types.
The natural mapping for individual columns of a table to a Java primitive wrapper or simple Object is that specified by the Data Type Conversion Tables in the JDBC standard. Those tables also specify the allowed data type conversions between data types supported by the data source and Java primitive wrapper types and simple objects when data is selected from or inserted into a data source.
For example, you could use the simple Object type java.lang.String as a target for the result of a SELECT statement on a column that is defined with the CHAR data type.
You could use the primitive wrapper class Float as a target for the result of a SELECT statement on a column that is defined as DECIMAL(5,2).
An application needing the set of departments from the EMP table could execute a query, and store that query's results in a String array, using code like the following:
Connection con = DriverManager.getConnection(...);
Data db = DataFactory.getData(con);
String[] departmentList = db.queryArray(
"SELECT DISTINCT WORKDEPT FROM SAMPLE_SCHEMA.EMP",
String.class );
The above is an invocation of the generic method queryArray, defined as public <T> T[] queryArray (java.lang.String sql, Class<T> returnClass, Object... parameters).