Java Doc for Query.java in  » Development » JoSQL » org » josql » Java Source Code / Java DocumentationJava Source Code and Java Documentation

Basic usage:

 Query q = new Query ();
 q.parse (myStatement);
 List results = q.execute (myObjects);
 

An example statement would look like:

 SELECT lastModified,
 name
 FROM   java.io.File
 WHERE  name LIKE '%.html'
 

The JoSQL functionality is large and complex, whilst basic queries like the one above are perfectly possible, very complex queries are also possible, for example:

 SELECT name,
 formatDate(lastModified),
 formatNumber(length),
 formatNumber(length - @avg_length),
 formatTimeDuration(@max_last_modified - lastModified)
 FROM   java.io.File
 WHERE  lastModified > @avg_last_modified
 AND    length > @avg_length
 AND    lower(name) LIKE '%.html'
 GROUP BY path
 ORDER BY name, lastModified DESC
 EXECUTE ON ALL avg (:_allobjs, length) avg_length,
 avg (:_allobjs, lastModified) avg_last_modified,
 max (:_allobjs, lastModified) max_last_modified
 

Note: the "EXECUTE ON ALL" syntax is an extension used by JoSQL because it has no notion of "aggregate functions".

For full details of how a query works and what is possible, see the JoSQL User Manual.

Please note that the package structure for JoSQL is deliberate, JoSQL is designed to be a black box and lightweight thus only the Query object and associated exceptions are exposed in the main package. Also, the class structure for JoSQL is not designed to exactly represent the SQL statement passed to it, rather the classes are optimised for ease of execution of the statement. If you wish to have a completely accurate Java object view of ANY SQL statement then please see: JSqlParser which will provide what you need.

For example:

 SELECT name,
 directory,
 file
 length
 FROM   java.io.File
 

 Query q = new Query ();
 q.parse (sql);
 // Note: this call will cause the entire statement to be executed.
 q.reorder (myFiles,
 "name DESC, 3 ASC, length, 1 DESC");
 

It is therefore possible to modify the orderbys in place, perhaps by using a different expression or changing the direction (since the objects are not cloned before being returned). However do so at YOUR OWN RISK. If you do so, then ensure you call: Query.setOrderByColumns(List) , then: Query.initOrderByComparator() before re-executing the statement, otherwise nothing will happen! The order bys.

For example:

 SELECT name,
 directory,
 file
 length
 FROM   java.io.File
 

 Query q = new Query ();
 q.parse (sql);
 Map reorderBys = new TreeMap ();
 reorderBys.put (new Integer (2), Query.ORDER_BY_ASC);
 reorderBys.put (new Integer (3), Query.ORDER_BY_DESC);
 reorderBys.put (new Integer (1), Query.ORDER_BY_ASC);
 reorderBys.put (new Integer (4), Query.ORDER_BY_DESC);
 // Note: this call will cause the entire statement to be executed.
 q.reorder (myFiles,
 reorderBys);
 

For example:

 SELECT name,
 directory,
 file
 length
 FROM   java.io.File
 

 Query q = new Query ();
 q.parse (sql);
 // Note: this call will cause the entire statement to be executed.
 q.reorder (myFiles,
 "name DESC, 3 ASC, length, 1 DESC");
 

YOU HAVE BEEN WARNED!!! NO BUGS WILL BE ACCEPTED THAT ARISE FROM THE CALLING OF THIS METHOD!!!
Parameters:
  c - The FROM class.