Java in-memory SQL Table as a data structure

Question

Several times, I wanted the data structure to look like an SQL table where you can select different fields and several fields. Like implementing SQL in memory, except that I do not want to store this many objects in the data structure.

I also require the object to be serializable using standard Java tools.

I did this before with a few hash tables or custom hash keys, but it ended up with a lot of code and a very specific problem.

I also used Groovy with its closing ability and gpath to help, but I do not always have it available (different projects).

EDIT: I think my problem is more likely related to the problem of traversing / selecting an object. Here are some interesting projects:

• http://josql.sourceforge.net/
• http://homepages.mcs.vuw.ac.nz/~djp/JQL/
• http://today.java.net/pub/a/today/2006/08/03/java-object-querying-using-jxpath.html
• http://code.google.com/p/lambdaj/ (I used this in the past and it was ... slow ...)
• http://jedi.codehaus.org/ Jedi

However, the drawback of most of these projects is that they are much slower than accessing objects directly (uneven receiver / setter) and, of course, slower than the index (hash).

Answer 1

JavaDB and HSQLDB , among others, have fully integrated databases.

Answer 2

What about using SQL in-memory for these purposes? You would save a ton of development time; operational overhead is really negligible. You risk much more by trying to implement this yourself.