INSTALLATION:

    $ perl Makefile.PL
    $ make
    $ make install

NOTE: There is no test against a "live" datasource anymore. Please edit the
      sybase.t.removed and move it to t/sybase.t if you'd like to perform one.


Modification log
--------------------------------------------------------------------------------
Version  Date     Author         Notes
-------- -------- -------------- -----------------------------------------------
   0.05  9/01     Andrei Nossov  Removed $self->debug() and test against Sybase
   0.04  3/01     Andrei Nossov  Root compound key bug fixed
   0.03  11/00    Andrei Nossov  Bug fixes, more documentation
   0.02  10/00    Andrei Nossov  Documentation improved
   0.01  8/00     Andrei Nossov  First cut
--------------------------------------------------------------------------------

NAME

DBIx::XMLMessage - XML Message exchange between DBI data sources



--------------------------------------------------------------------------------

SYNOPSIS


--------------------------------------------------------------------------------

OUTBOUND MESSAGE

    #!/usr/bin/perl



    use DBI;
    use DBIx::XMLMessage;



    # Template string
    my $tpl_str =<< "_EOT_";
    <?xml version="1.0" encoding="UTF-8" ?>
    <TEMPLATE NAME='SysLogins' TYPE='XML' VERSION='1.0' TABLE='syslogins'>
    <KEY NAME='suid' DATATYPE='NUMERIC' PARENT_NAME='OBJECT_ID' />
    <COLUMN NAME='LoginId' EXPR='suid' DATATYPE='NUMERIC' />
    <COLUMN NAME='PasswordDate' EXPR='pwdate' DATATYPE='DATETIME'
        BLTIN="fix_gmdatetime" />
    <CHILD NAME='SysUsers' TABLE='sysusers'>
        <KEY NAME='suid' PARENT_NAME='LoginId' DATATYPE='NUMERIC' />
        <COLUMN NAME='UserId' EXPR='uid' DATATYPE='NUMERIC' />
        <COLUMN NAME='UserName' EXPR='name' />
    </CHILD>
    </TEMPLATE>
    _EOT_
    my $msg = new DBIx::XMLMessage ('TemplateString' => $tpl_str);
    my $ghash = { 'OBJECT_ID' => [ 1, 2 ] };
    my $dbh = DBI->connect('dbi:Sybase:server=x;database=master','sa','secret');
    $msg->rexec ($dbh, $ghash);



    print "\n\n", $msg->output_xml(0,0);
    print "\n\n", $msg->output_xml(0,1);




--------------------------------------------------------------------------------

INBOUND MESSAGE

    #!/usr/bin/perl



    use DBI;
    use DBIx::XMLMessage;



    my $template_xml =<< "_EOD1_";
    <?xml version="1.0" encoding="UTF-8" ?>
    <TEMPLATE NAME='SysLogins' TYPE='XML' VERSION='1.0' TABLE='syslogins'
        ACTION='SAVE'>
    <KEY NAME='suid' DATATYPE='NUMERIC' PARENT_NAME='OBJECT_ID' />
    <COLUMN NAME='LoginId' EXPR='suid' DATATYPE='NUMERIC' />
    <COLUMN NAME='PasswordDate' EXPR='pwdate' DATATYPE='DATETIME'
        BLTIN="fix_gmdatetime" />
    <CHILD NAME='SysUsers' TABLE='sysusers'>
        <KEY NAME='suid' PARENT_NAME='LoginId' DATATYPE='NUMERIC' />
        <COLUMN NAME='UserId' EXPR='uid' DATATYPE='NUMERIC' />
        <COLUMN NAME='UserName' EXPR='name' />
    </CHILD>
    </TEMPLATE>
    _EOD1_



    my $message_xml =<< "_EOD2_";
    <?xml version="1.0" encoding="UTF-8"?>
    <SysLogins>
    <LoginId>1</LoginId>
    <PasswordDate>1999/08/17 08:31</PasswordDate>
    <SysUsers>
        <UserId>1</UserId>
        <UserName>sa</UserName>
    </SysUsers>
    </SysLogins>
    _EOD2_



    my $xmlmsg = new DBIx::XMLMessage ('TemplateString' => $template_xml);
    my $msgtype = $xmlmsg->input_xml($message_xml);
    my $ghash = {
        'OBJECT_ID' => [ 1 ]
    };
    $xmlmsg->populate_objects ($ghash);



    my $dbh = DBI->connect('dbi:Sybase:server=x;database=master','sa','secret');
    $xmlmsg->rexec ($dbh, $ghash);
    print $xmlmsg->output_message();




--------------------------------------------------------------------------------

DESCRIPTION
The package maintains simple XML templates that describe object structure.

The package is capable of generating SQL statements based on these templates
and executing them against DBI data sources. After executing the SQL, the package
formats the data results into XML strings. E.g. the following simple template


    <TEMPLATE NAME='SysLogins' TYPE='XML' VERSION='1.0' TABLE='syslogins'
        ACTION='SAVE'>
    <KEY NAME='suid' DATATYPE='NUMERIC' PARENT_NAME='OBJECT_ID' />
    <COLUMN NAME='LoginId' EXPR='suid' DATATYPE='NUMERIC' />
    </TEMPLATE>


being executed with key value = 1, will be tranlated into this SQL:

SELECT suid LoginId FROM syslogins where suid = 1

and the result will be formatted into this XML string:


    <SysLogins>
        <LoginId>1<LoginId>
    </SysLogins>


Inbound messages can be processed according to the same kind of templates and
the database is updated accordingly. Templates are capable of defining the SQL
operators, plus new SAVE operation which is basically a combination of SELECT
and either INSERT or UPDATE depending on whether the record was found by the
compound key value or not.



--------------------------------------------------------------------------------

SALES PITCH
This package allows for objects exchange between different databases. They could
be from different vendors, as long as they both have DBD drivers. In certain
cases it is even possible to exchange objects between databases with different
data models. Publishing of databases on the web could potentially be one of the
applications as well.



--------------------------------------------------------------------------------

TEMPLATE TAGS


--------------------------------------------------------------------------------

TEMPLATE
This is manadatory top-level tag. It can correspond to a certain table and be
processed just like table-level REFERENCE and CHILD attributes described below.
Some of TEMPLATE attributes are related to the whole template (e.g. TYPE or
VERSION) while others desribe the table ti's based on (e.g. TABLE)

If the TABLE attribute is defined, the generated SQL is going to run against
some table. Otherwise a SQL with no table will be generated. This only makes
sense for outbound messages and only possible on certain engines, like Sybase.
Also, the immediate child columns should contain constants only for apparent
reasons.



--------------------------------------------------------------------------------

REFERENCE
REFERENCE is a table-level tag. It's meant to represent a single record from
another table that's retrieved by unique key. E.g. if my current table is EMPL
then DEPARTMENT would be a REFERENCE since employee can have no more than one
departament.



--------------------------------------------------------------------------------

CHILD
This tag meant to represent a number of child records usually retrieved by a
foreign key value (probably primary key of the current table). Right now there's
no difference in processing between CHILD and REFERENCE, but it may appear in the
future releases.



--------------------------------------------------------------------------------

COLUMN
This tag is pretty self-explanatory. Each COLUMN tag will appear on the SELECT,
INSERT or UPDATE list of the generated SQL.



--------------------------------------------------------------------------------

KEY
Key represents linkage of this table's records to the parent table. All KEY's
will appear on the WHERE clause as AND components. This way of linkage is typical
for most of relational systems and considered to be a good style. I guess it
shouldn't be much of a restriction anyway. If it gets that, you could try tweak
up the WHERE_CLAUSE attribute..



--------------------------------------------------------------------------------

PARAMETER
This tag represents a parameter that will be passsed to a stored procedure.
Currently, only Sybase-style stored procedures are supported, i.e.

exec proc_name @param_name = 'param_value', ...

Fixes for Oracle, DB2 and Informix are welcome..



--------------------------------------------------------------------------------

TEMPLATE TAG ATTRIBUTES


--------------------------------------------------------------------------------

NAME

    Applicable to:  All template tags
    Required for:   All template tags


NAME is the only required attribute for all of the template tags. The main
purpose of it is to specify the tag name as it will appear in the resulting XML
document. Also, depending on the template tag type (COLUMN, PARAMETER and KEY)
it may serve as default value for EXPR discussed below. Here's a small example
of how it works. If my column is represented in the template like this:


    <COLUMN NAME='ObjectId' />


the resulting SQL will contain


    SELECT ObjectID, ...


whereas if I have


    <COLUMN NAME='ObjectId' EXPR='igObjectId' />


it will generate the following SQL:


    SELECT igObjectId ObjectID, ...


I.e. in the latter example, NAME used as an alias and EXPR as a real database
column name. The column in the first example has no alias.



--------------------------------------------------------------------------------

ACTION

    Applicable to:  TEMPLATE, REFERENCE, CHILD
    Required for:   None


Possible values for this attibute are SELECT, INSERT, UPDATE, EXEC and SAVE. If
action is not provided, it is assumed that t he action should be SELECT. The
first 4 values correspond to SQL data management operators (EXEC is
vendor-specific and represents execution of a stored procedure). The fifth
value, SAVE, is basically a combination of SELECT and either INSERT or UPDATE,
depending on whether the record was found by the compound key value or not. This
often helps to avoid usage of complicated stored procedures with primary key
generation and keep things generic and scalable. Primary key generation issue is
addressed separately by using of the GENERATE_PK attribute (see below).



--------------------------------------------------------------------------------

BLTIN

    Applicable to:  COLUMN
    Required for:   None


Represents a perl built-in function. before invocation of this subroutine the
package prepares array @_ and makes it visible to the built-in function. The 3
arguments received by the built-in are: $self - DBIx::XMLMessage object $node -
Correspondent DBIx::XMLMessage::COLUMN object. You can use it to obtain other
column attributes, e.g. $node->{DATATYPE} $value - The column value

Meaning of the value depends on direction of the message, i.e. whether the
message is inbound or outbound. In case of inbound message, this is the value
received by the package from outside world; if the message is inbound then this
is the value selected from database. There's one built-in function that comes
with the package -- fix_gmdatetime. It converts date and time to GMT for outbound
messages and from GMT to the database date/time for inbound messages. Just add
one attribute to your datetime column:


    ... BLTIN="fix_gmdatetime" ...




--------------------------------------------------------------------------------

CARDINALITY

    Applicable to:   KEY, PARAMETER, REFERENCE, CHILD
    Required for:    None
    Possible values: REQUIRED, OPTIONAL
    Default:         REQUIRED


This parameter has different meaning for different element types. Optional KEYs
and PARAMETERs allow to proceed execution if the value for it was not found at
some point of execution. Optional CHILDs and REFERENCEs will be skipped from
execution, and hence from output, if the package failed to collect all the key
values.



--------------------------------------------------------------------------------

DATATYPE

    Applicable to:   KEY, PARAMETER, COLUMN
    Required for:    None
    Possible values: CHAR, VARCHAR, VARCHAR2, DATE, DATETIME, NUMERIC
    Default:         CHAR


This attribute loosely corresponds to the database column type. The only
processing difference in the core package is quoting of the non-numeric
datatypes, particularly those containign substrings CHAR, DATE or TIME. The
built-in fix_gmdatetime utilizes this attribute more extensively.



--------------------------------------------------------------------------------

DEBUG
Recognized but not currently supported



--------------------------------------------------------------------------------

DEFAULT

    Applicable to:   PARAMETER, COLUMN
    Required for:    None
    Possible values: Any string or number


This attribute allows to provide a default value for COLUMNs and PARAMETERS.
Please note that default values are not being formatted, so they have to
represent the literal value. E.g. if you want to provide a string DEFAULT it
would look somewhat like this: ... DEFAULT = ``'UNKNOWN'''



--------------------------------------------------------------------------------

EXPR

    Applicable to:  All template tags
    Required for:   None


For COLUMN and KEY this attribute represents the actual database column name or
a constant. For PARAMETER



--------------------------------------------------------------------------------

FACE

    Applicable to:   COLUMN
    Required for:    None
    Possible values: ATTRIBUTE, TAG
    Default:         TAG


This attribute allows to output certain columns as attributes, as opposed to
the default TAG-fasion output. Since it's not supported for inbound messages
yet, usage of this feature is not recommended.



--------------------------------------------------------------------------------

GENERATE_PK

    Applicable to:   COLUMN
    Required for:    None
    Possible values: HASH, SQL returning one value or name


This attribute allows you to specify how to generate primary key values. You
have 2 options here:

1. You can write your own Perl function, put its reference to the global hash
under the name of the table for which you intend to generate primary key values
and provide the value of 'HASH' as the GENERATE_PK value

2. You can put the generating SQL block/statement into the GENERATE_PK value



--------------------------------------------------------------------------------

HIDDEN

    Applicable to:   COLUMN


Indicates that the column will be excluded from the output. This attribute only
makes sense for outbound messages.



--------------------------------------------------------------------------------

MAXROWS

Currently not supported. In future, intends to limits the number of selected
rows.



--------------------------------------------------------------------------------

PARENT_NAME

    Applicable to:   KEY


Indicates the name of the tag one level up to which this one tag is
corresponding. E.g.


    ...
    <COLUMN NAME='OBJECT_ID'/>
    <REFERENCE ...>
        <KEY NAME='nOrderId' PARENT_NAME='OBJECT_ID'/>
    </REFERENCE>


This feature is a workaround allowing to have two columns descending from the
same parent column at the same level. There was some other prolem it was helping
to resolve, but I forgot what it was ;^)



--------------------------------------------------------------------------------

PROC

    Applicable to:   TEMPLATE, REFERENCE, CHILD


Used in conjunction with ACTION='PROC'. Defines the name of the stored procedure
to invoke.



--------------------------------------------------------------------------------

RTRIMTEXT
Currently not supported. The package does automatic right-trimming for all the
character data.



--------------------------------------------------------------------------------

TABLE
Name of the table against which the SQL will be run.



--------------------------------------------------------------------------------

TOLERANCE

    Applicable to:   TEMPLATE, REFERENCE, CHILD
    Possible values: IGNORE, CREATE, REJECT
    Default:         IGNORE


Allows to adjust package behaviour when SQL execution produces unexpected result
columns. E.g. if there's a stored procedure that will return the results for your
message, you can omit describing of all the resulting COLUMNS in the template and
instead specify ... TOLERANCE='CREATE' Whatever columns are returned by the
stored procedure (Sybase & MS SQL) will be added on-the-fly and available for
the output.



--------------------------------------------------------------------------------

WHERE_CLAUSE
Additional where clause. Added as an AND component at the end of generated
where clause.



--------------------------------------------------------------------------------

METHODS


--------------------------------------------------------------------------------

new

    my $xmsg = new DBIx::XMLMessage (
        [ _OnError => $err_coderef, ]
        [ _OnTrace => $trace_coderef, ]
        [ _OnDebug => $debug_coderef, ]
        [ Handlers => $expat_handlers_hashref, ]
        [ TemplateString => $xml_template_as_a_string, ]
        [ TemplateFile => $xml_template_file_name, ]
    )


You can specify either TemplateString or TemplateFile, but not both. If any of
those specified, the template will be parsed.



--------------------------------------------------------------------------------

set_handlers

    $xmsg->set_handlers ($expat_handlers_hashref)


Set additional expat handlers, see XML::Parser::Expat. Normally you won't use
this. The only case I could think of is processing of encoding..



--------------------------------------------------------------------------------

prepare_template

    $xmsg->prepare_template ($template_xml_string)


This method can be invoked if the template was not specified in the 'new'
method invocation.



--------------------------------------------------------------------------------

prepare_template_from_file

    $xmsg->prepare_template_from_file ($template_file_name)


Same as above, but template is read from file here.



--------------------------------------------------------------------------------

input_xml

    $xmsg->input_xml ($inbound_xml_message_content)


Parse an inbound XML message. The values form this message will be used to fill
in COLUMNS and PARAMETERS. The structure of this message should comply with
template. Uses Tree parsing style.



--------------------------------------------------------------------------------

input_xml_file

    $xmsg->input_xml_file ($inbound_xml_message_file_name)


Same as above, but the XML message is read from a file.



--------------------------------------------------------------------------------

populate_objects

    $xmsg->populate_objects ($global_hash_ref [, $matching_object
        [, $tag_name [, $tag_content, [$parameter_index]]]])


This method is trying to stuff the existing template with the inbound message
previously parsed by one of the 'input_xml' methods. The only mandatory
attribute is global hash reference, which has to contain key values for the
topmost tag TEMPLATE.



--------------------------------------------------------------------------------

rexec

    $xmsg->rexec ($dbh, $global_hash_ref)


This method is running the created query against a DBI/DBD source and fills in
the template with results in order to make them available for subsequent
output_message call. In case of INSERT/UPDATE operations only key values will
be filled in.



--------------------------------------------------------------------------------

output_message
This method returns a string with query results in XML format suitable for
printing or whatever manupulations seem appropriate.



--------------------------------------------------------------------------------

SEE ALSO

    DBI
    DBD
    XML::Parser
    XML::Parser::Expat




--------------------------------------------------------------------------------

AUTHORS

  Andrei Nossov <andrein@andrein.com>


This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself