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

      use XML::Parser;

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

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

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

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

      open(my $fh, 'xmlgenerator |');
      $p3->parse($foo, ProtocolEncoding => 'ISO-8859-1');

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

    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 "STYLES" 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.

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

        *   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.

        *   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.

        *   Pkg

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

        *   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.

        *   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.

        *   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

        *   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.

        *   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

        *   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

        *   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.

        *   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

        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

    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.

    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

  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

    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
    containing 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.

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

    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.

    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.

    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.

    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:

    *   StartDocument

        Called at the start of the parse .

    *   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.

    *   EndTag

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

    *   Text

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

    *   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.

    *   EndDocument

        Called at conclusion of the parse.

    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.

    Larry Wall <> wrote version 1.0.

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

    Matt Sergeant <> is now maintaining XML::Parser