Answers to the FAQ

Q1. What is DB Mapper?
A1. DB Mapper is a Java package which provides powerful functionality to Java applications that interact with a JDBC-capable relational database. By providing various interfaces and classes that implement a type of Data Access Object (DAO) pattern, the DB Mapper package eliminates need for an application to write any SQL statements to perform the typical create, retrieve, update, and delete (CRUD) operations on a database.
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Q2. Where can I find the latest distribution of DB Mapper?
A2. The DB Mapper distribution is hosted at NEC ONSD software group website.
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Q3. How is DB Mapper licensed?
A3. DB Mapper Free for personal use and moderately priced for commercial use. Refer to the licensing agreement or contact the ONSD Software Group at onsd@necam.com for details.
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Q4. Where can I get the source code to DB Mapper package?
A4. Please see the ONSD Software Group pages for licensing agreement,   downloads and contact information.
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Q5. How do I report bugs or request enhancement?
A5. For information on submitting questions or bugs or other technical support please see our support options. Try to provide as much detail as possible, such as version of DB Mapper you are using, a short example reproducing the problem etc.
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Q6. Does DB Mapper support my database?
A6. Ideally, to use DB Mapper, you will need to have access to a relational database server and Java class libraries that include a JDBC 2.0 compliant driver class. The examples provided with DB Mapper distribution have been tested with a variety of popular JDBC-capable RDBMS products, such as Oracle 8.0 and 8i (http://www.oracle.com/), MySQL 3.23.39 (http://www.mysql.com/), PostGres 7.2.2 (http://www.postgresql.org/), HyperSonic Database 1.7.1( http://hsqldb.sourceforge.net/).
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Q7. Does DB Mapper comply with the SUN's JDO specification?
A7. No, DB Mapper doesn't comply with the SUN's JDO specification.
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Q8. Is DB Mapper thread-safe?
A8. Yes, DB Mapper is designed to work well with multi-threaded applications.
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Q9. What is a class mapping and do I need to create one before I can crate or retrieve a Java object from a database?
A9. DB Mapper requires some specific information about the objects to be saved, and the database to which they are saved. The class mapping includes information such as which tables and columns of the database are used to store the various fields of the class.
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Q10. Do I need to recompile my application each time I add or modify a business class?
A10. No. DB Mapper is based on "write once, persist anywhere" DAO pattern. DB Mapper uses OR mapping and java reflection API to map java class to relation database tables.
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Q11. Where class mappings are specified and can they be created or modified at run time?
A11. The most common way to specify class mappings is to use an OR mapping XML file(s) (See user guide "Creating an object-relational (OR) mapping file" for a more detailed discussion on the OR mapping XML file format.). However, its possible to a new class mappings or modify an existing class mapping using DB Mapper API, please refer to DB Mapper javadoc documentaion (included with distribution) for details.
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Q12. Do I always need to define primary key for a class mapping?
A12. No. The definition of a primary key for a class that uses the DB Mapper package is optional. However, most of the operations such as updating objects, deleting or finding objects by key, etc., do require that a primary key be defined, that can be used to uniquely identify a Java object in database.
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Q13. Do I always need to define primary key class for a class mapping?
A13. No. Only some of the DBInterface methods, such as findByPrimaryKey(), or findAllPrimaryKeys(), require that a primary key class be defined. In the case where a primary key consists of a single key field, there is no need for an application to define a primary key class.
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Q14. Can DB Mapper be used for entity bean persistence?
A14. Yes. DB Mapper can used by an application programmer as a persistence mechanism for BMP (bean managed persistence) entity beans. See user guide "EJB Example" for more details.
On the other hand, DB Mapper can be used by an EJB container vendor as a persistence mechanism for CMP (container managed persistence) entity beans.
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Q15. Is there any GUI tool to create/update the DB Mapper XML configuration files?
A15. No. The current DB Mapper distribution does not include any GUI tool to modify or create XML configuration files. However creating or editing DB Mapper XML files are quite easy and straight, and discussed in detail in the user guide.
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