sql2java: Object-Relational Mapping Tool for Java

Overview
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Note: I haven't updated this project in a while. However, Florent Ramiere has started a SourceForge project based on this codebase. Check it out at: http://sql2java.sourceforge.net.

Overview

sql2java is a free, open source tool that enables Java developers to quickly map a relational database schema to a set of classes. These classes can be supplemented with your own methods and used within any Java application. The generated source code uses standard JDBC methods for persistence, and there is no runtime library required.

Mapping Philosophy

Different object-relational mapping tools have different philosophies about how to do the mapping. Some tools are very flexible, and allow you to combine fields from multiple tables to form a single class. Others don't generate source code, but instead rely on a configuration file, and generate dynamic SQL at runtime. sql2java takes a pretty simple approach to the problem. Each table is mapped to two different classes:

A core class that represents a single row in the table. Each column is mapped to a property in the class, and get/set methods are provided to access or modify that property.
A manager class that encapsulates all JDBC code for reading/writing to that table. This class provides lifecycle methods for loading, saving, and deleting rows in the table. Core objects are returned from the load methods, and core objects can be saved simply by calling a save() method. Managers are singletons in the system. That is, only one instance of each Manager should exist in the VM. All Manager classes descend from a Manager base class that you will customize after the first time you run the mapping tool. This base class dispenses JDBC connections to the managers, and serves as a place where you can stick utility code that managers should have access to.

Requirements:

JDBC compliant database (only tested with Oracle and MySQL)

Examples

CHANGE log
example README
Sample schema
ProductFamily.java - sample core class generated from the above schema
ProductFamilyManager.java - sample manager class generated from the above schema

0.94 has added MySQL support. Testing was done with version 1.2c of the mm driver. Note that this driver (and our verison of MySQL - 3.21.29) do not support foreign keys, so the generated manager classes don't have the fancy load methods that classes generated against Oracle have. The StoreClientMysql class was written to reflect this (it doesn't call the non-existent methods).

To use s2j with MySQL, make sure your s2j.properties file contains:

writer=com.bitmechanic.sql2java.MysqlManagerWriter

Unlike the Oracle support, which I've tested on production code on a work related project, the MySQL support has only be tested with the StoreClientMysql class. Please let us know (using the eGroup below) if you experience problems with the MySQL support, as it may otherwise go undetected.

Unfortunately, I haven't been able to keep everything up to date. Here are the current problems:

Developer docs still don't explain how to use the new overloaded load methods to specify individual columns to load. Someday..

Mailing List and Wiki

To discuss this project, visit our eGroups page: http://www.egroups.com/group/s2j.

There is also a Wiki for discussing this project.

Download

Version Release Date Download Developer Docs

0.94 July 6, 2000 tar.gz - zip HTML MS Word

0.93 June 30, 2000 tar.gz - zip HTML MS Word

0.92 April 15, 2000 tar.gz - zip HTML MS Word

0.91 April 11, 2000 tar.gz - zip HTML MS Word

0.90 March 4, 2000 tar.gz - zip HTML MS Word

NOTE: This software is distributed under the terms of the GNU Public License. You are free to download, use, and modify this software under the terms of this license.

Version	Release Date	Download	Developer Docs
0.94	July 6, 2000	tar.gz - zip	HTML MS Word
0.93	June 30, 2000	tar.gz - zip	HTML MS Word
0.92	April 15, 2000	tar.gz - zip	HTML MS Word
0.91	April 11, 2000	tar.gz - zip	HTML MS Word
0.90	March 4, 2000	tar.gz - zip	HTML MS Word

Related Projects

Here are links to other object relational mapping tools for Java:

TableGen - Free (GPL) O-R mapper for Java. Looks a lot like s2j!
DbGen - Lightweight O-R mapper for Java. Web site claims it may go open source. Has a GUI to manage the mapping process.
CocoBase - From Thought Inc. This is a commercial tool that supports EJB, RMI, etc. A few different pricing tiers, and trial download.
JavaBlend - Sun's O-R mapper. Looks pretty sophisticated, but I've not tried it.
TOPLink - The mother of all O-R mappers. I've installed an eval, and it's quite sophisticated. Has been purchased by BEA for inclusion in their WebGain tool suite.
DataGrinder - Another commercial O-R mapper.

Here are links to some articles about O-R mapping:

Scott Ambler's O-R mapping white paper - A really good discussion of O-R mapping.

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