Description:

The open source Web-2-Database System (also known as the 'web2database' or W2DBML system) is an XML language and associated Java package to reduce the need to hard-code Java server-side code to a given database schema. Also, the package features extra support for dynamic Web clients. The W2DBML System has high aims and has already attained some altitude. Its Gnu General Public License encourages the pooling of many talents to improve it.  Sourceforge.net helps to host this project.   Download links are below.

Description Detail:

The W2DBML System currently powers Phraseologic, a Web-based collaborative Phraseology. The Web2Database Java package automates and organizes the Java servlet-based process of taking incoming HTML form data, validating it, and writing it to a database, and supports fully dynamic and data-centric logic on the Web client (browser). The only potentially database-specific call it uses is the 'Statement.getLastInsertId()' method from MySQL's JDBC driver "org.git.mm.mysql" (used for obtaining the last row updated). A database-independent way of doing this, "getGeneratedKeys", should be upcoming.

Specifically, Web2Database supports incoming HTML form name-value pairs (in Java HTTPServletRequests) organized partially or wholly into any number of sets of name-value pairs. This support allows client logic (for example, JavaScript living on a Web browser) to dynamically generate as many sets of form elements as are needed by the end user, without being limited by a static HTML form. Currently, the dynamically generated sets of name-value pairs must follow a basic pattern, detailed elsewhere in the documentation.

Uses: Use the Web2Database package (inluding its XML dialect) to minimize changes to your Java servlets and other Java server-side code across changes in database input validation, database schema, and database type, and to support dynamic Web clients. Also use this API to completely organize your database validation constraints and target JDBC datatypes. This package abstracts database column value validation, database schema, and target JDBC datatypes completely out of servlet code that saves incoming HTML form data to a database.

Specifics: Web2Database gives a Java servlet-based Web application permanent datastructure access to the required information about the application's data storage facilities, schema, and kinds of HTML form inputs. The information covers the databases, database tables, database table referential integrity, database table special characteristics, table rows, table columns, the corresponding HTML form inputs to the table columns, and the validation parameters to be applied.

Web2Database provides this information by using the separate Java package, the JDOM API, to read an XML file of the dialect 'W2DBML' version 1.0.

Web2Database provides access to objects that offer:

• A list of the databases available, in the order that they are to be written to.
• A list of the tables in each database, in the order that they are to be written to, including information about each table.
• A list of the columns in each table, in the order that they exist in the table row, including information about each table.
• Information about any HTML form-input element corresponding to a given database column, including regular expression information for processing the HTML form-element name (key) or value.
• A printed list of the data read from the application-specific W2DBML XML file, displayed by default in the ServletContext's log file. The servlet log file is located under the servlet engine's home directory. This provides a visual check that the Java is reading the XML file as intended.

This code is best viewed on a 21" screen (indentation set for this screen width).

Be sure to read the documentation for this class' 'writeToDatabase' method to see the important current limitations of this package.

Areas for Improvement:

• Several classes in the 'dbDictionary', 'dataModel', and 'tags' packages need to know about identifiers used in the W2DBML language definition (DTD or schema). Make them learn what they need to know about the language definition by querying the DOM via JDOM, just as they obtain the application-specific settings of a given application-specific W2DBML file by querying the DOM via JDOM.
• Move the SELECT query building out of the 'httpservlet' package and into the 'query' package.
• Come up with and implement new object abstractions to simplify the conditional logic in the 'Web2Database.writeDatabase' method, and to shorten the 'Web2Database' class. Things got a little bit overgrown there, and before any new functionality is added to the 'Web2Database' package, there needs to be some more decomposition of logic into objects.
• Currently, referential integrity and unique-columns are supported, but not selective update has not been tested. Test and if necessary make modifications to support selective update. With selective update, for example, a user could change their e-mail contact information.
• In its present form, this package is best used for executing discrete database write operations that are fairly uniform in length, because its sychronization is not very fine-grained. Refine the granularity of the synchronization.
• Presently, the Web2Database class is a servlet. It is a servlet whose unique functionality can easily be accessed by another servlet via the 'writeToDatabase' method. And, it can easily be customized. But perhaps it would be very useful to extract all non-servlet-specific functionality out of Web2Database so that any servlet, not just a Web2Database servlet, could easily use it.
• Currently, a weak entity table that does not contain any column elements whose incoming matching HTML/DOM form elements are dynamically generated on the client is only protected from unnecessary writing by W2DBML unique constraints. This is definitely sufficient but it is a s-l-o-w way to go about things. In fact, currently it is the only remaining 'slow' aspect of the W2DBML system. Optimally, the system would keep track of such tables (for example, in the seventh test database, 'contact_permissions') and skip them entirely once they have been written to.
• Decompose the 'ColumnElement' class into three subtypes, one for each type of column element, leaving 'ColumnElement' as an abstract class.
• Add database connection pooling.

Links:

• Download the latest Web-2-Database release! -- Sourceforge.net hosts this project, including its downloads.
• JavaDoc for the 'web2database' Java package
• The W2DBML DTD
• An example W2DBML file
• Phraseologic, an application powered by the W2DBML System.

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