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Parser(3pm)           User Contributed Perl Documentation          Parser(3pm)



NAME
       XML::Parser - A perl module for parsing XML documents

SYNOPSIS
         use XML::Parser;

         $p1 = new XML::Parser(Style => 'Debug');
         $p1->parsefile('REC-xml-19980210.xml');
         $p1->parse('<foo id="me">Hello World</foo>');

         # Alternative
         $p2 = new XML::Parser(Handlers => {Start => \&handle_start,
                                            End   => \&handle_end,
                                            Char  => \&handle_char});
         $p2->parse($socket);

         # Another alternative
         $p3 = new XML::Parser(ErrorContext => 2);

         $p3->setHandlers(Char    => \&text,
                          Default => \&other);

         open(FOO, 'xmlgenerator |');
         $p3->parse(*FOO, ProtocolEncoding => 'ISO-8859-1');
         close(FOO);

         $p3->parsefile('junk.xml', ErrorContext => 3);

DESCRIPTION
       This module provides ways to parse XML documents. It is built on top of
       XML::Parser::Expat, which is a lower level interface to James Clark's
       expat library. Each call to one of the parsing methods creates a new
       instance of XML::Parser::Expat which is then used to parse the
       document.  Expat options may be provided when the XML::Parser object is
       created.  These options are then passed on to the Expat object on each
       parse call.  They can also be given as extra arguments to the parse
       methods, in which case they override options given at XML::Parser
       creation time.

       The behavior of the parser is controlled either by "Style" and/or
       "Handlers" options, or by "setHandlers" method. These all provide
       mechanisms for XML::Parser to set the handlers needed by
       XML::Parser::Expat.  If neither "Style" nor "Handlers" are specified,
       then parsing just checks the document for being well-formed.

       When underlying handlers get called, they receive as their first
       parameter the Expat object, not the Parser object.

METHODS
       new This is a class method, the constructor for XML::Parser. Options
           are passed as keyword value pairs. Recognized options are:

           o   Style

               This option provides an easy way to create a given style of
               parser. The built in styles are: "Debug", "Subs", "Tree",
               "Objects", and "Stream". These are all defined in separate
               packages under "XML::Parser::Style::*", and you can find
               further documentation for each style both below, and in those
               packages.

               Custom styles can be provided by giving a full package name
               containing at least one '::'. This package should then have
               subs defined for each handler it wishes to have installed. See
               "STYLES" below for a discussion of each built in style.

           o   Handlers

               When provided, this option should be an anonymous hash
               containing as keys the type of handler and as values a sub
               reference to handle that type of event. All the handlers get
               passed as their 1st parameter the instance of expat that is
               parsing the document. Further details on handlers can be found
               in "HANDLERS". Any handler set here overrides the corresponding
               handler set with the Style option.

           o   Pkg

               Some styles will refer to subs defined in this package. If not
               provided, it defaults to the package which called the
               constructor.

           o   ErrorContext

               This is an Expat option. When this option is defined, errors
               are reported in context. The value should be the number of
               lines to show on either side of the line in which the error
               occurred.

           o   ProtocolEncoding

               This is an Expat option. This sets the protocol encoding name.
               It defaults to none. The built-in encodings are: "UTF-8",
               "ISO-8859-1", "UTF-16", and "US-ASCII". Other encodings may be
               used if they have encoding maps in one of the directories in
               the @Encoding_Path list. Check "ENCODINGS" for more information
               on encoding maps. Setting the protocol encoding overrides any
               encoding in the XML declaration.

           o   Namespaces

               This is an Expat option. If this is set to a true value, then
               namespace processing is done during the parse. See "Namespaces"
               in XML::Parser::Expat for further discussion of namespace
               processing.

           o   NoExpand

               This is an Expat option. Normally, the parser will try to
               expand references to entities defined in the internal subset.
               If this option is set to a true value, and a default handler is
               also set, then the default handler will be called when an
               entity reference is seen in text. This has no effect if a
               default handler has not been registered, and it has no effect
               on the expansion of entity references inside attribute values.

           o   Stream_Delimiter

               This is an Expat option. It takes a string value. When this
               string is found alone on a line while parsing from a stream,
               then the parse is ended as if it saw an end of file. The
               intended use is with a stream of xml documents in a MIME
               multipart format. The string should not contain a trailing
               newline.

           o   ParseParamEnt

               This is an Expat option. Unless standalone is set to "yes" in
               the XML declaration, setting this to a true value allows the
               external DTD to be read, and parameter entities to be parsed
               and expanded.

           o   NoLWP

               This option has no effect if the ExternEnt or ExternEntFin
               handlers are directly set. Otherwise, if true, it forces the
               use of a file based external entity handler.

           o   Non-Expat-Options

               If provided, this should be an anonymous hash whose keys are
               options that shouldn't be passed to Expat. This should only be
               of concern to those subclassing XML::Parser.

       setHandlers(TYPE, HANDLER [, TYPE, HANDLER [...]])
           This method registers handlers for various parser events. It
           overrides any previous handlers registered through the Style or
           Handler options or through earlier calls to setHandlers. By
           providing a false or undefined value as the handler, the existing
           handler can be unset.

           This method returns a list of type, handler pairs corresponding to
           the input. The handlers returned are the ones that were in effect
           prior to the call.

           See a description of the handler types in "HANDLERS".

       parse(SOURCE [, OPT => OPT_VALUE [...]])
           The SOURCE parameter should either be a string containing the whole
           XML document, or it should be an open IO::Handle. Constructor
           options to XML::Parser::Expat given as keyword-value pairs may
           follow the SOURCE parameter. These override, for this call, any
           options or attributes passed through from the XML::Parser instance.

           A die call is thrown if a parse error occurs. Otherwise it will
           return 1 or whatever is returned from the Final handler, if one is
           installed.  In other words, what parse may return depends on the
           style.

       parsestring
           This is just an alias for parse for backwards compatibility.

       parsefile(FILE [, OPT => OPT_VALUE [...]])
           Open FILE for reading, then call parse with the open handle. The
           file is closed no matter how parse returns. Returns what parse
           returns.

       parse_start([ OPT => OPT_VALUE [...]])
           Create and return a new instance of XML::Parser::ExpatNB.
           Constructor options may be provided. If an init handler has been
           provided, it is called before returning the ExpatNB object.
           Documents are parsed by making incremental calls to the parse_more
           method of this object, which takes a string. A single call to the
           parse_done method of this object, which takes no arguments,
           indicates that the document is finished.

           If there is a final handler installed, it is executed by the
           parse_done method before returning and the parse_done method
           returns whatever is returned by the final handler.

HANDLERS
       Expat is an event based parser. As the parser recognizes parts of the
       document (say the start or end tag for an XML element), then any
       handlers registered for that type of an event are called with suitable
       parameters.  All handlers receive an instance of XML::Parser::Expat as
       their first argument. See "METHODS" in XML::Parser::Expat for a
       discussion of the methods that can be called on this object.

       Init                (Expat)

       This is called just before the parsing of the document starts.

       Final                (Expat)

       This is called just after parsing has finished, but only if no errors
       occurred during the parse. Parse returns what this returns.

       Start                (Expat, Element [, Attr, Val [,...]])

       This event is generated when an XML start tag is recognized. Element is
       the name of the XML element type that is opened with the start tag. The
       Attr & Val pairs are generated for each attribute in the start tag.

       End                (Expat, Element)

       This event is generated when an XML end tag is recognized. Note that an
       XML empty tag (<foo/>) generates both a start and an end event.

       Char                (Expat, String)

       This event is generated when non-markup is recognized. The non-markup
       sequence of characters is in String. A single non-markup sequence of
       characters may generate multiple calls to this handler. Whatever the
       encoding of the string in the original document, this is given to the
       handler in UTF-8.

       Proc                (Expat, Target, Data)

       This event is generated when a processing instruction is recognized.

       Comment                (Expat, Data)

       This event is generated when a comment is recognized.

       CdataStart        (Expat)

       This is called at the start of a CDATA section.

       CdataEnd                (Expat)

       This is called at the end of a CDATA section.

       Default                (Expat, String)

       This is called for any characters that don't have a registered handler.
       This includes both characters that are part of markup for which no
       events are generated (markup declarations) and characters that could
       generate events, but for which no handler has been registered.

       Whatever the encoding in the original document, the string is returned
       to the handler in UTF-8.

       Unparsed                (Expat, Entity, Base, Sysid, Pubid, Notation)

       This is called for a declaration of an unparsed entity. Entity is the
       name of the entity. Base is the base to be used for resolving a
       relative URI.  Sysid is the system id. Pubid is the public id. Notation
       is the notation name. Base and Pubid may be undefined.

       Notation                (Expat, Notation, Base, Sysid, Pubid)

       This is called for a declaration of notation. Notation is the notation
       name.  Base is the base to be used for resolving a relative URI. Sysid
       is the system id. Pubid is the public id. Base, Sysid, and Pubid may
       all be undefined.

       ExternEnt        (Expat, Base, Sysid, Pubid)

       This is called when an external entity is referenced. Base is the base
       to be used for resolving a relative URI. Sysid is the system id. Pubid
       is the public id. Base, and Pubid may be undefined.

       This handler should either return a string, which represents the
       contents of the external entity, or return an open filehandle that can
       be read to obtain the contents of the external entity, or return undef,
       which indicates the external entity couldn't be found and will generate
       a parse error.

       If an open filehandle is returned, it must be returned as either a glob
       (*FOO) or as a reference to a glob (e.g. an instance of IO::Handle).

       A default handler is installed for this event. The default handler is
       XML::Parser::lwp_ext_ent_handler unless the NoLWP option was provided
       with a true value, otherwise XML::Parser::file_ext_ent_handler is the
       default handler for external entities. Even without the NoLWP option,
       if the URI or LWP modules are missing, the file based handler ends up
       being used after giving a warning on the first external entity
       reference.

       The LWP external entity handler will use proxies defined in the
       environment (http_proxy, ftp_proxy, etc.).

       Please note that the LWP external entity handler reads the entire
       entity into a string and returns it, where as the file handler opens a
       filehandle.

       Also note that the file external entity handler will likely choke on
       absolute URIs or file names that don't fit the conventions of the local
       operating system.

       The expat base method can be used to set a basename for relative
       pathnames. If no basename is given, or if the basename is itself a
       relative name, then it is relative to the current working directory.

       ExternEntFin        (Expat)

       This is called after parsing an external entity. It's not called unless
       an ExternEnt handler is also set. There is a default handler installed
       that pairs with the default ExternEnt handler.

       If you're going to install your own ExternEnt handler, then you should
       set (or unset) this handler too.

       Entity                (Expat, Name, Val, Sysid, Pubid, Ndata, IsParam)

       This is called when an entity is declared. For internal entities, the
       Val parameter will contain the value and the remaining three parameters
       will be undefined. For external entities, the Val parameter will be
       undefined, the Sysid parameter will have the system id, the Pubid
       parameter will have the public id if it was provided (it will be
       undefined otherwise), the Ndata parameter will contain the notation for
       unparsed entities. If this is a parameter entity declaration, then the
       IsParam parameter is true.

       Note that this handler and the Unparsed handler above overlap. If both
       are set, then this handler will not be called for unparsed entities.

       Element                (Expat, Name, Model)

       The element handler is called when an element declaration is found.
       Name is the element name, and Model is the content model as an
       XML::Parser::Content object. See "XML::Parser::ContentModel Methods" in
       XML::Parser::Expat for methods available for this class.

       Attlist                (Expat, Elname, Attname, Type, Default, Fixed)

       This handler is called for each attribute in an ATTLIST declaration.
       So an ATTLIST declaration that has multiple attributes will generate
       multiple calls to this handler. The Elname parameter is the name of the
       element with which the attribute is being associated. The Attname
       parameter is the name of the attribute. Type is the attribute type,
       given as a string. Default is the default value, which will either be
       "#REQUIRED", "#IMPLIED" or a quoted string (i.e. the returned string
       will begin and end with a quote character).  If Fixed is true, then
       this is a fixed attribute.

       Doctype                (Expat, Name, Sysid, Pubid, Internal)

       This handler is called for DOCTYPE declarations. Name is the document
       type name. Sysid is the system id of the document type, if it was
       provided, otherwise it's undefined. Pubid is the public id of the
       document type, which will be undefined if no public id was given.
       Internal is the internal subset, given as a string. If there was no
       internal subset, it will be undefined. Internal will contain all
       whitespace, comments, processing instructions, and declarations seen in
       the internal subset. The declarations will be there whether or not they
       have been processed by another handler (except for unparsed entities
       processed by the Unparsed handler). However, comments and processing
       instructions will not appear if they've been processed by their
       respective handlers.

       * DoctypeFin                (Parser)

       This handler is called after parsing of the DOCTYPE declaration has
       finished, including any internal or external DTD declarations.

       XMLDecl                (Expat, Version, Encoding, Standalone)

       This handler is called for xml declarations. Version is a string
       containg the version. Encoding is either undefined or contains an
       encoding string.  Standalone will be either true, false, or undefined
       if the standalone attribute is yes, no, or not made respectively.

STYLES
       Debug

       This just prints out the document in outline form. Nothing special is
       returned by parse.

       Subs

       Each time an element starts, a sub by that name in the package
       specified by the Pkg option is called with the same parameters that the
       Start handler gets called with.

       Each time an element ends, a sub with that name appended with an
       underscore ("_"), is called with the same parameters that the End
       handler gets called with.

       Nothing special is returned by parse.

       Tree

       Parse will return a parse tree for the document. Each node in the tree
       takes the form of a tag, content pair. Text nodes are represented with
       a pseudo-tag of "0" and the string that is their content. For elements,
       the content is an array reference. The first item in the array is a
       (possibly empty) hash reference containing attributes. The remainder of
       the array is a sequence of tag-content pairs representing the content
       of the element.

       So for example the result of parsing:

         <foo><head id="a">Hello <em>there</em></head><bar>Howdy<ref/></bar>do</foo>

       would be:

                    Tag   Content
         ==================================================================
         [foo, [{}, head, [{id => "a"}, 0, "Hello ",  em, [{}, 0, "there"]],
                     bar, [         {}, 0, "Howdy",  ref, [{}]],
                       0, "do"
               ]
         ]

       The root document "foo", has 3 children: a "head" element, a "bar"
       element and the text "do". After the empty attribute hash, these are
       represented in it's contents by 3 tag-content pairs.

       Objects

       This is similar to the Tree style, except that a hash object is created
       for each element. The corresponding object will be in the class whose
       name is created by appending "::" and the element name to the package
       set with the Pkg option. Non-markup text will be in the ::Characters
       class. The contents of the corresponding object will be in an anonymous
       array that is the value of the Kids property for that object.

       Stream

       This style also uses the Pkg package. If none of the subs that this
       style looks for is there, then the effect of parsing with this style is
       to print a canonical copy of the document without comments or
       declarations.  All the subs receive as their 1st parameter the Expat
       instance for the document they're parsing.

       It looks for the following routines:

       o   StartDocument

           Called at the start of the parse .

       o   StartTag

           Called for every start tag with a second parameter of the element
           type. The $_ variable will contain a copy of the tag and the %_
           variable will contain attribute values supplied for that element.

       o   EndTag

           Called for every end tag with a second parameter of the element
           type. The $_ variable will contain a copy of the end tag.

       o   Text

           Called just before start or end tags with accumulated non-markup
           text in the $_ variable.

       o   PI

           Called for processing instructions. The $_ variable will contain a
           copy of the PI and the target and data are sent as 2nd and 3rd
           parameters respectively.

       o   EndDocument

           Called at conclusion of the parse.

ENCODINGS
       XML documents may be encoded in character sets other than Unicode as
       long as they may be mapped into the Unicode character set. Expat has
       further restrictions on encodings. Read the xmlparse.h header file in
       the expat distribution to see details on these restrictions.

       Expat has built-in encodings for: "UTF-8", "ISO-8859-1", "UTF-16", and
       "US-ASCII". Encodings are set either through the XML declaration
       encoding attribute or through the ProtocolEncoding option to
       XML::Parser or XML::Parser::Expat.

       For encodings other than the built-ins, expat calls the function
       load_encoding in the Expat package with the encoding name. This
       function looks for a file in the path list
       @XML::Parser::Expat::Encoding_Path, that matches the lower-cased name
       with a '.enc' extension. The first one it finds, it loads.

       If you wish to build your own encoding maps, check out the
       XML::Encoding module from CPAN.

AUTHORS
       Larry Wall <larry@wall.org> wrote version 1.0.

       Clark Cooper <coopercc@netheaven.com> picked up support, changed the
       API for this version (2.x), provided documentation, and added some
       standard package features.

       Matt Sergeant <matt@sergeant.org> is now maintaining XML::Parser

POD ERRORS
       Hey! The above document had some coding errors, which are explained
       below:

       Around line 362:
           '=begin' only takes one parameter, not several as in '=begin man
           .ds PI PI'

       Around line 365:
           =end man without matching =begin.  (Stack: [empty])



perl v5.10.0                      2007-11-20                       Parser(3pm)