[HAPI-devel] new way to get data from a message

[Tripp, B. <Bry...@uh...>]

There is a new class called ca.uhn.hl7v2.util.MessageQuery (in CVS now =
and
to be included in next release).  It's like Terser but with much better
support for repetitions. =20

It could use a few more features but works great for lots of cases.  See
unit tests for examples.  For your convenience the docs are included =
below.


Bryan =20

 * Queries messages in an SQL-like style.  We get repeated row-like=20
 * structures by looping over repetitions of groups, segments, or =
fields.=20
 *=20
 * LOOPING:   =20
 * You specify the loop points as part of the query.  For example you =
could=20
 * specify loop point x like this: <code>x =3D /.MSH-18(*)</code>.  The =
*=20
 * is replaced by numbers 0, 1, 2, etc. as you loop through the results, =

 * so this example would loop through repetitions of MSH-18.  If=20
 * there are multiple loop points, the loops are nested so that each
possible=20
 * combination is returned.  Looping stops when none of the fields under =
a=20
 * loop point are valued.  The name of the loop point ('x' in the =
example=20
 * above) is arbitrary.       =20
 *=20
 * SELECTING FIELDS:=20
 * The syntax is similar to SQL, except that Terser paths are used in =
place
 * of table.field.  You can use the "as" keyword to give a field a name,
like=20
 * this: <code>select /.MSH-7 as msg_date</code>.  If your field is =
under=20
 * a loop point, replace the path up to the loop point with a loop point =

 * reference, like this: <code>select {foo}-1 loop foo =3D =
/.PID-3(*)</code>
 *=20
 * SELECTING ROWS:
 * A "row" is a combination of all selected fields at one iteration.  =
You=20
 * can filter which rows are returned using a where clause similar to =
that
 * in SQL.  Use exact values or regular expressions, for example:=20
 * <code>where {1} like '.*blood.*'</code> or <code>where {1}/PID-3-1 =
=3D
'111'</code>
 * Multiple filters can be separated with commas (which mean 'and').  =
Future
 * versions may support 'or', negation, brackets, etc., but this version
doesn't. =20
 *=20
 * FULL EXAMPLE:=20
 * select {pat-id}-1 as id loop pat-id =3D ./PID-3(*) where {pat-id}-2 =
=3D 'mrn'
 *=20
 * SUBTLETIES OF LOOPING:=20
 * A loop point can be under another loop point.  For example consider =
the
message:  =20
 *=20
 * MSH|etc.|etc.
 * Z01|one~two|a
 * Z01|three~four|b
 *=20
 * The query, "select {a}-2, {b} loop a =3D /Z01(*), b =3D {a}-1(*)" =
would
return:=20
 * a one
 * a two=20
 * b three
 * b four
 *=20
 * While the query "select {a}-2, {b} loop a =3D /Z01(*), b =3D =
/Z01(1)-1(*)"
would return:
 * a one
 * a two=20
 * b one
 * b two
 *=20
 * In the first case, one loop point refers to another.  In the second =
case
the loops=20
 * are treated as independent, just as if they referred to different
branches of the=20
 * message. =20