Hydrate 2.0 review

Hydrate is a Java tool that provides for fast efficient and error-free transformation of data between three different representations

License: LGPL (GNU Lesser General Public License) File size: 0K Developer: David Chamberlin

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Hydrate is a Java tool that provides for fast efficient and error-free transformation of data between three different representations: relational databases, objects in an object-oriented programming language and extended markup language (XML).

Each of these representations has its strengths and weaknesses as shown in the diagram below; but which should you use as a basis for your application design?

Hydrate relaxes some of the pressure on this decision by providing tools for moving data from one representation to another, guided by a master UML class representation of that data.

You want to lay a domain object model view over an existing database or set of databases. Hydrate gives you the tools to design that model in UML and map your existing data to that model. Once in the object space, you can perform complex manipulations on the objects, calculate results and save information back to a relational cache for searching or reloading, as well as converting the results to XML for sending to downstream systems or transforming to a readable format for display.
Your project involves taking various data files fed from external systems that you want to pull into an object model on your server before writing the results down to a fully relational database. You can now respond to requests from external systems by rehydrating the data from its relational form and sending it out as XML documents or transforming those documents to a readable format for display.
You are building a data warehouse in which you have the broad specifications for the model, but want to provide for flexibility and adaptability for future unpredicted requests. Based on a core data model, Hydrate gives you the tools to create you database schema, and write information to it, but more significantly to subsequently lay a completely different object model perhaps aggregating some of the data over the top of that schema to process it in unforeseen ways.
You need to integrate data from many different data sources in a highly performant manner. SQL permits you to read a huge data set a row at a time and perform running calculations and filtering on that data. But the performance pressures can lead to code that is highly coupled with the database and what do you do if you need to integrate data from elsewhere in order to complete your calculations? Hydrate permits you to operate in the object space and integrate information from other sources on-the-fly.

Here are some key features of "Hydrate":
To integrate legacy and other data schemas over which you have little control. Map data from many different data sources into a single self-consistent in-memory model. Different parts of the same object, as well as different sub-populations of the same object type can be drawn from different data sources, different schemas and even different database architectures.
Load, populate and connect up multiple object types from a single query. There is no limit to the number of object types that can be loaded from a single query, or to the complexity of the relationships that can be resolved between them. Objects read from a query are automatically merged into objects already in memory.
Full control over the SQL that runs against the database (if you need it). Any SQL queries simultaneously from multiple JDBC drivers, even using database specific optimizations, as long as they returns a result set.
Access and manipulate the same data through the rich and powerful XML toolset. Use the same meta data that describes your objects to easily read from, write to and validate any consistent XML schema. Use XML for display, data transmission or XSLT transformation. Load XML data back into objects.
Highly optimized performance for reading and writing SQL and XML. Since native types are used and SQL chatter is non-existent, database performance is comparable with doing the mapping by hand. XML reading and writing uses SAX exclusively.