What is JoSQL?

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For example, to find all the HTML files that have been modified in December 2004:

SELECT * FROM java.io.File WHERE name $ LIKE "%.html" AND toDate (lastModified) BETWEEN toDate ('01-12-2004') AND toDate ('31-12-2004')

AND length > 20000



JoSQL treats each object as a "row" from a table/view and thus each of the accessible methods/fields from the object are therefore "columns" that can be accessed. JoSQL takes this one step further by allowing the full object-tree to be accessed. Taking java.io.File as an example again, it is possible to perform searches on the last modified time of the "parent" File, thus:

SELECT * FROM java.io.File WHERE toDate (parentFile.lastModified) BETWEEN toDate ('01-12-2004') AND toDate ('31-12-2004') AND parentFile.name = "local" JoSQL (SQL for Java Objects) provides the ability for a developer to apply a SQL statement to a collection of Java Objects. JoSQL provides the ability to search, order and group ANY Java objects and should be applied when you want to perform SQL-like queries on a collection of Java Objects.For example, to find all the HTML files that have been modified in December 2004:Now to do this in Java code would require the creation of a custom function that will allow the comparison between 2 java.io.File objects. Doesn't sound hard? Probably not, but what if you now wanted to also compare by the length of the file as well? That is a hard-code change that will then require recompilation and testing. However with JoSQL it's as easy as adding:to the end of the query.JoSQL treats each object as a "row" from a table/view and thus each of the accessible methods/fields from the object are therefore "columns" that can be accessed. JoSQL takes this one step further by allowing the full object-tree to be accessed. Taking java.io.File as an example again, it is possible to perform searches on the last modified time of the "parent" File, thus:

Quick Start



List myObjs = getMyObjects (); Query q = new Query (); q.parse ( "SELECT * FROM java.io.File WHERE name LIKE '%.java'" ); QueryResults qr = q.execute (myObjs); List res = qr.getResults (); for ( int i = 0; i < res.size (); i++) { File f = (File) res.get (i); } advanced example.

List myObjs = getMyObjects (); Query q = new Query (); q.parse ( "SELECT name,length " + "FROM java.io.File " + "WHERE fileExtension (name) = :fileExt " + "ORDER BY length DESC, name " + "EXECUTE ON RESULTS avg (:_allobjs, length) avgLength" ); q.setVariable ( "fileExt", "java" ); QueryResults qr = q.execute (myObjs); Map saveValues = qr.getSaveValues (); Number avg = (Number) saveValues.get ( "avgLength" ); List res = qr.getResults (); for ( int i = 0; i < res.size (); i++) { List r = (List) res.get (i); System.out.println ( "NAME: " + r.get (0)); System.out.println ( "LENGTH: " + r.get (1) + ", AVG: " + avg); } For those who don't have time to read the manual , here's a quick example to get you started.And a moreexample.

What JoSQL ISN'T

A common misconception about JoSQL is that it is a database tool. It's not, it is merely a way of using SQL to perform data selection, grouping and ordering operations on Java objects. Java currently has no method of performing searching, sorting and grouping without writing far too much code.



JoSQL is designed to bridge the gap. It should not be used to replace a standard RDBMS or even a OODBMS (such as db4o, although I wish they would support SQL queries, then I might consider using it ;), JoSQL has it's place and should be an addition to your toolkit not a replacement for any particular item.

