Package org.htmlparser

Class Parser

  • All Implemented Interfaces:
    java.io.Serializable, ConnectionMonitor
    public class Parser
extends java.lang.Object
implements java.io.Serializable, ConnectionMonitor
    The main parser class. This is the primary class of the HTML Parser library. It provides constructors that take a String, a URLConnection, or a Lexer. In the case of a String, a check is made to see if the first non-whitespace character is a <, in which case it is assumed to be HTML. Otherwise an attempt is made to open it as a URL, and if that fails it assumes it is a local disk file. If you want to parse a String after using the no-args constructor, use setInputHTML(), or you can use createParser(java.lang.String, java.lang.String).

    The Parser provides access to the contents of the page, via a NodeIterator, a NodeList or a NodeVisitor.

    Typical usage of the parser is: 

     Parser parser = new Parser ("http://whatever");
 NodeList list = parser.parse (null);
 // do something with your list of nodes.

    What types of nodes and what can be done with them is dependant on the setup, but in general a node can be converted back to HTML and it's children (enclosed nodes) and parent can be obtained, because nodes are nested. See the Node interface.

    For example, if the URL contains:
    {@.html Mondays -- What a bad idea. Most people have a pathological hatred of Mondays... }
    and the example code above is used, the list contain only one element, the {@.html } node. This node is a tag, which is an object of class Html if the default NodeFactory (a PrototypicalNodeFactory) is used.

    To get at further content, the children of the top level nodes must be examined. When digging through a node list one must be conscious of the possibility of whitespace between nodes, e.g. in the example above: 

     Node node = list.elementAt (0);
 NodeList sublist = node.getChildren ();
 System.out.println (sublist.size ());
    would print out 5, not 2, because there are newlines after {@.html }, {@.html } and {@.html } that are children of the HTML node besides the {@.html } and {@.html } nodes.

    Because processing nodes is so common, two interfaces are provided to ease this task, filters and visitors.

    See Also:
    Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      Parser()
      Zero argument constructor.
      Parser​(java.lang.String resource)
      Creates a Parser object with the location of the resource (URL or file).
      Parser​(java.lang.String resource, ParserFeedback feedback)
      Creates a Parser object with the location of the resource (URL or file) You would typically create a DefaultHTMLParserFeedback object and pass it in.
      Parser​(java.net.URLConnection connection)
      Construct a parser using the provided URLConnection.
      Parser​(java.net.URLConnection connection, ParserFeedback fb)
      Constructor for custom HTTP access.
      Parser​(Lexer lexer)
      Construct a parser using the provided lexer.
      Parser​(Lexer lexer, ParserFeedback fb)
      Construct a parser using the provided lexer and feedback object.

    • Field Detail

      • VERSION_NUMBER

        public static final double VERSION_NUMBER
        The floating point version number (1.6).
        See Also:
        Constant Field Values

      • VERSION_TYPE

        public static final java.lang.String VERSION_TYPE
        The type of version ("Release Build").
        See Also:
        Constant Field Values

      • VERSION_DATE

        public static final java.lang.String VERSION_DATE
        The date of the version ("Jun 10, 2006").
        See Also:
        Constant Field Values

      • VERSION_STRING

        public static final java.lang.String VERSION_STRING
        The display version ("1.6 (Release Build Jun 10, 2006)").
        See Also:
        Constant Field Values

      • mLexer

        protected Lexer mLexer
        The html lexer associated with this parser.

      • DEVNULL

        public static final ParserFeedback DEVNULL
        A quiet message sink. Use this for no feedback.

      • STDOUT

        public static final ParserFeedback STDOUT
        A verbose message sink. Use this for output on System.out.

    • Constructor Detail

      • Parser

        public Parser​(Lexer lexer,
              ParserFeedback fb)
        Construct a parser using the provided lexer and feedback object. This would be used to create a parser for special cases where the normal creation of a lexer on a URLConnection needs to be customized.
        Parameters:
        lexer - The lexer to draw characters from.
        fb - The object to use when information, warning and error messages are produced. If null no feedback is provided.

      • Parser

        public Parser​(java.net.URLConnection connection,
              ParserFeedback fb)
       throws ParserException
        Constructor for custom HTTP access. This would be used to create a parser for a URLConnection that needs a special setup or negotiation conditioning beyond what is available from the ConnectionManager.
        Parameters:
        connection - A fully conditioned connection. The connect() method will be called so it need not be connected yet.
        fb - The object to use for message communication.
        Throws:
        ParserException - If the creation of the underlying Lexer cannot be performed.

      • Parser

        public Parser​(java.lang.String resource,
              ParserFeedback feedback)
       throws ParserException
        Creates a Parser object with the location of the resource (URL or file) You would typically create a DefaultHTMLParserFeedback object and pass it in.
        Parameters:
        resource - Either a URL, a filename or a string of HTML. The string is considered HTML if the first non-whitespace character is a <. The use of a url or file is autodetected by first attempting to open the resource as a URL, if that fails it is assumed to be a file name. A standard HTTP GET is performed to read the content of the URL.
        feedback - The HTMLParserFeedback object to use when information, warning and error messages are produced. If null no feedback is provided.
        Throws:
        ParserException - If the URL is invalid.
        See Also:
        Parser(URLConnection,ParserFeedback)

      • Parser

        public Parser​(java.lang.String resource)
       throws ParserException
        Creates a Parser object with the location of the resource (URL or file). A DefaultHTMLParserFeedback object is used for feedback.
        Parameters:
        resource - Either HTML, a URL or a filename (autodetects).
        Throws:
        ParserException - If the resourceLocn argument does not resolve to a valid page or file.
        See Also:
        Parser(String,ParserFeedback)

      • Parser

        public Parser​(Lexer lexer)
        Construct a parser using the provided lexer. A feedback object printing to System.out is used. This would be used to create a parser for special cases where the normal creation of a lexer on a URLConnection needs to be customized.
        Parameters:
        lexer - The lexer to draw characters from.

      • Parser

        public Parser​(java.net.URLConnection connection)
       throws ParserException
        Construct a parser using the provided URLConnection. This would be used to create a parser for a URLConnection that needs a special setup or negotiation conditioning beyond what is available from the ConnectionManager. A feedback object printing to System.out is used.
        Parameters:
        connection - A fully conditioned connection. The connect() method will be called so it need not be connected yet.
        Throws:
        ParserException - If the creation of the underlying Lexer cannot be performed.
        See Also:
        Parser(URLConnection,ParserFeedback)

    • Method Detail

      • getVersion

        public static java.lang.String getVersion()
        Return the version string of this parser.
        Returns:
        A string of the form: 
         "[floating point number] ([build-type] [build-date])"

      • getVersionNumber

        public static double getVersionNumber()
        Return the version number of this parser.
        Returns:
        A floating point number, the whole number part is the major version, and the fractional part is the minor version.

      • setConnectionManager

        public static void setConnectionManager​(ConnectionManager manager)
        Set the connection manager all Parsers use.
        Parameters:
        manager - The new connection manager.
        See Also:
        getConnectionManager()

      • createParser

        public static Parser createParser​(java.lang.String html,
                                  java.lang.String charset)
        Creates the parser on an input string.
        Parameters:
        html - The string containing HTML.
        charset - Optional. The character set encoding that will be reported by getEncoding(). If charset is null the default character set is used.
        Returns:
        A parser with the html string as input.
        Throws:
        java.lang.IllegalArgumentException - if html is null.

      • setResource

        public void setResource​(java.lang.String resource)
                 throws ParserException
        Set the html, a url, or a file.
        Parameters:
        resource - The resource to use.
        Throws:
        java.lang.IllegalArgumentException - if resource is null.
        ParserException - if a problem occurs in connecting.

      • setConnection

        public void setConnection​(java.net.URLConnection connection)
                   throws ParserException
        Set the connection for this parser. This method creates a new Lexer reading from the connection.
        Parameters:
        connection - A fully conditioned connection. The connect() method will be called so it need not be connected yet.
        Throws:
        ParserException - if the character set specified in the HTTP header is not supported, or an i/o exception occurs creating the lexer.
        java.lang.IllegalArgumentException - if connection is null.
        ParserException - if a problem occurs in connecting.
        See Also:
        setLexer(org.htmlparser.lexer.Lexer), getConnection()

      • setURL

        public void setURL​(java.lang.String url)
            throws ParserException
        Set the URL for this parser. This method creates a new Lexer reading from the given URL. Trying to set the url to null or an empty string is a no-op.
        Parameters:
        url - The new URL for the parser.
        Throws:
        ParserException - If the url is invalid or creation of the underlying Lexer cannot be performed.
        ParserException - if a problem occurs in connecting.
        See Also:
        getURL()

      • getURL

        public java.lang.String getURL()
        Return the current URL being parsed.
        Returns:
        The current url. This is the URL for the current page. A string passed into the constructor or set via setURL may be altered, for example, a file name may be modified to be a URL.
        See Also:
        Page.getUrl(), setURL(java.lang.String)

      • setEncoding

        public void setEncoding​(java.lang.String encoding)
                 throws ParserException
        Set the encoding for the page this parser is reading from.
        Parameters:
        encoding - The new character set to use.
        Throws:
        ParserException - If the encoding change causes characters that have already been consumed to differ from the characters that would have been seen had the new encoding been in force.
        See Also:
        EncodingChangeException, getEncoding()

      • getEncoding

        public java.lang.String getEncoding()
        Get the encoding for the page this parser is reading from. This item is set from the HTTP header but may be overridden by meta tags in the head, so this may change after the head has been parsed.
        Returns:
        The encoding currently in force.
        See Also:
        setEncoding(java.lang.String)

      • setLexer

        public void setLexer​(Lexer lexer)
        Set the lexer for this parser. The current NodeFactory is transferred to (set on) the given lexer, since the lexer owns the node factory object. It does not adjust the feedback object.
        Parameters:
        lexer - The lexer object to use.
        Throws:
        java.lang.IllegalArgumentException - if lexer is null.
        See Also:
        setNodeFactory(org.htmlparser.NodeFactory), getLexer()

      • setNodeFactory

        public void setNodeFactory​(NodeFactory factory)
        Set the current node factory.
        Parameters:
        factory - The new node factory for the current lexer.
        Throws:
        java.lang.IllegalArgumentException - if factory is null.
        See Also:
        getNodeFactory()

      • reset

        public void reset()
        Reset the parser to start from the beginning again. This assumes support for a reset from the underlying Source object.

        This is cheaper (in terms of time) than resetting the URL, i.e. 

         parser.setURL (parser.getURL ());
        because the page is not refetched from the internet. Note: the nodes returned on the second parse are new nodes and not the same nodes returned on the first parse. If you want the same nodes for re-use, collect them in a NodeList with parse(null) and operate on the NodeList.

      • elements

        public NodeIterator elements()
                      throws ParserException
        Returns an iterator (enumeration) over the html nodes. Nodes can be of three main types: In general, when parsing with an iterator or processing a NodeList, you will need to use recursion. For example: 
         void processMyNodes (Node node)
 {
     if (node instanceof TextNode)
     {
         // downcast to TextNode
         TextNode text = (TextNode)node;
         // do whatever processing you want with the text
         System.out.println (text.getText ());
     }
     if (node instanceof RemarkNode)
     {
         // downcast to RemarkNode
         RemarkNode remark = (RemarkNode)node;
         // do whatever processing you want with the comment
     }
     else if (node instanceof TagNode)
     {
         // downcast to TagNode
         TagNode tag = (TagNode)node;
         // do whatever processing you want with the tag itself
         // ...
         // process recursively (nodes within nodes) via getChildren()
         NodeList nl = tag.getChildren ();
         if (null != nl)
             for (NodeIterator i = nl.elements (); i.hasMoreElements (); )
                 processMyNodes (i.nextNode ());
     }
 }

 Parser parser = new Parser ("http://www.yahoo.com");
 for (NodeIterator i = parser.elements (); i.hasMoreElements (); )
     processMyNodes (i.nextNode ());
        Returns:
        An iterator over the top level nodes (usually {@.html }).
        Throws:
        ParserException - If a parsing error occurs.

      • parse

        public NodeList parse​(NodeFilter filter)
               throws ParserException
        Parse the given resource, using the filter provided. This can be used to extract information from specific nodes. When used with a null filter it returns an entire page which can then be modified and converted back to HTML (Note: the synthesis use-case is not handled very well; the parser is more often used to extract information from a web page).

        For example, to replace the entire contents of the HEAD with a single TITLE tag you could do this: 

         NodeList nl = parser.parse (null); // here is your two node list
 NodeList heads = nl.extractAllNodesThatMatch (new TagNameFilter ("HEAD"))
 if (heads.size () > 0) // there may not be a HEAD tag
 {
     Head head = heads.elementAt (0); // there should be only one
     head.removeAll (); // clean out the contents
     Tag title = new TitleTag ();
     title.setTagName ("title");
     title.setChildren (new NodeList (new TextNode ("The New Title")));
     Tag title_end = new TitleTag ();
     title_end.setTagName ("/title");
     title.setEndTag (title_end);
     head.add (title);
 }
 System.out.println (nl.toHtml ()); // output the modified HTML
        Parameters:
        filter - The filter to apply to the parsed nodes, or null to retrieve all the top level nodes.
        Returns:
        The list of matching nodes (for a null filter this is all the top level nodes).
        Throws:
        ParserException - If a parsing error occurs.

      • visitAllNodesWith

        public void visitAllNodesWith​(NodeVisitor visitor)
                       throws ParserException
        Apply the given visitor to the current page. The visitor is passed to the accept() method of each node in the page in a depth first traversal. The visitor beginParsing() method is called prior to processing the page and finishedParsing() is called after the processing.
        Parameters:
        visitor - The visitor to visit all nodes with.
        Throws:
        ParserException - If a parse error occurs while traversing the page with the visitor.

      • setInputHTML

        public void setInputHTML​(java.lang.String inputHTML)
                  throws ParserException
        Initializes the parser with the given input HTML String.
        Parameters:
        inputHTML - the input HTML that is to be parsed.
        Throws:
        ParserException - If a error occurs in setting up the underlying Lexer.
        java.lang.IllegalArgumentException - if inputHTML is null.

      • extractAllNodesThatMatch

        public NodeList extractAllNodesThatMatch​(NodeFilter filter)
                                  throws ParserException
        Extract all nodes matching the given filter.
        Parameters:
        filter - The filter to be applied to the nodes.
        Returns:
        A list of nodes matching the filter criteria, i.e. for which the filter's accept method returned true.
        Throws:
        ParserException - If a parse error occurs.
        See Also:
        Node.collectInto(NodeList, NodeFilter)

      • main

        public static void main​(java.lang.String[] args)
        The main program, which can be executed from the command line.
        Parameters:
        args - A URL or file name to parse, and an optional tag name to be used as a filter.