NAME¶

XML::Filter::Merger - Assemble multiple SAX streams in to one document

VERSION¶

version 0.46

SYNOPSIS¶

    ## See XML::SAX::Manifold and XML::SAX::ByRecord for easy ways
    ## to use this processor.
    my $w = XML::SAX::Writer->new(           Output => \*STDOUT );
    my $h = XML::Filter::Merger->new(        Handler => $w );
    my $p = XML::SAX::ParserFactory->parser( Handler => $h );
    ## To insert second and later docs in to the first doc:
    $h->start_manifold_document( {} );
    $p->parse_file( $_ ) for @ARGV;
    $h->end_manifold_document( {} );
    ## To insert multiple docs inline (especially useful if
    ## a subclass does the inline parse):
    $h->start_document( {} );
    $h->start_element( { ... } );
    ....
    $h->start_element( { Name => "foo", ... } );
    $p->parse_uri( $uri );   ## Body of $uri inserted in <foo>...</foo>
    $h->end_element( { Name => "foo", ... } );
    ...

DESCRIPTION¶

Combines several documents in to one "manifold" document. This can be done in two ways, both of which start by parsing a master document in to which (the guts of) secondary documents will be inserted.

    my $h = XML::Filter::Merger->new( Handler => $w );
    $h->start_document( {} );
    $h->start_element( { Name => "foo1" } );
        $p->parse_string( "<foo2><baz /></foo2>" );
    $h->end_element( { Name => "foo1" } );
    $h->end_document( {} );

    package Subclass;
    use vars qw( @ISA );
    @ISA = qw( XML::Filter::Merger );
    sub characters {
        my $self = shift;
        return $self->SUPER::characters( @_ )  ## **
            unless $self->in_master_document;  ## **
        my $r = $self->SUPER::characters( @_ );
        $self->set_include_all_roots( 1 );
        XML::SAX::PurePerl->new( Handler => $self )->parse_string( "<hey/>" );
        return $r;
    }
    ## **: It is often important to use the recursion guard shown here
    ## to protect the decision making logic that should only be run on
    ## the events in the master document from being run on events in the
    ## subdocument.  Of course, if you want to apply the logic
    ## recursively, just leave the guard code out (and, yes, in this
    ## example, th guard code is phrased in a slightly redundant fashion,
    ## but we want to make the idiom clear).

    $h->start_manifold_document( {} );
    $p->parse_string( "<foo1><bar /></foo1>" );
    $p->parse_string( "<foo2><baz /></foo2>" );
    $h->end_manifold_document( {} );

NAME¶

XML::Filter::Merger - Assemble multiple SAX streams in to one document

METHODS¶

new

    my $d = XML::Filter::Merger->new( \%options );
    

reset

Clears the filter after an accident. Useful when reusing the filter. new() and start_manifold_document() both call this.

start_manifold_document

This must be called before the master document's "start_document()" if you want XML::Filter::Merger to insert documents that will be sent after the master document.

It does not need to be called if you are going to insert secondary documents by sending their events in the midst of processing the master document.

It is passed an empty ({}) data structure.

Additional Methods¶

These are provided to make it easy for subclasses to find out roughly where they are in the document structure. Generally, these should be called after calling SUPER::start_...() and before calling SUPER::end_...() to be accurate.

in_master_document

Returns TRUE if the current event is in the first top level document.

document_depth

Gets how many nested documents surround the current document. 0 means that you are in a top level document. In manifold mode, This may or may not be a secondary document: secondary documents may also follow the primary document, in which case they have a document depth of 0.

element_depth

Gets how many nested elements surround the current element in the current input document. Does not count elements from documents surrounding this document.

top_level_document_number

Returns the number of the top level document in a manifold document. This is 0 for the first top level document, which is always the master document.

end_manifold_document

This must be called after the last document's end_document is called. It is passed an empty ({}) data structure which is passed on to the next processor's end_document() call. This call also causes the end_element() for the root element to be passed on.

set_include_all_roots

    $h->set_include_all_roots( 1 );
    

Setting this option causes the merger to include all root element nodes, not just the first document's. This means that later documents are treated as subdocuments of the output document, rather than as envelopes carrying subdocuments.

Given two documents received are:

 Doc1:   <root1><foo></root1>
 Doc1:   <root2><bar></root2>
 Doc3:   <root3><baz></root3>
    

then with this option cleared (the default), the result looks like:

    <root1><foo><bar><baz></root1>
    

. This is useful when processing document oriented XML and each upstream filter channel gets a complete copy of the document. This is the case with the machine XML::SAX::Manifold and the splitting filter XML::Filter::Distributor.

With this option set, the result looks like:

    <root1><foo><root2><bar></root2><root3><baz></root3></root1>
    

This is useful when processing record oriented XML, where the first document only contains the preamble and postamble for the records and not all of the records. This is the case with the machine XML::SAX::ByRecord and the splitting filter XML::Filter::DocSplitter.

The two splitter filters mentioned set this feature appropriately.

LIMITATIONS¶

The events before and after a secondary document's root element events are discarded. It is conceivable that characters, PIs and commentary outside the root element might need to be kept. This may be added as an option.

The DocumentLocators are not properly managed: they should be saved and restored around each each secondary document.

Does not yet buffer all events after the first document's root end_element event.

If these bite you, contact me.

AUTHOR¶

    Barrie Slaymaker <barries@slaysys.com>

COPYRIGHT¶

    Copyright 2002, Barrie Slaymaker, All Rights Reserved.

You may use this module under the terms of the Artistic, GNU Public, or BSD licenses, you choice.

AUTHORS¶

• Barry Slaymaker
• Chris Prather <chris@prather.org>

COPYRIGHT AND LICENSE¶

This software is copyright (c) 2013 by Barry Slaymaker.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.