tag.java

一个用java语言编写的网络爬虫程序

     * converted with toHTMLAttributeName(). 
     * @return copy of this tag with named attribute removed.  The copy is 
     * a region of a fresh page containing only the tag. 
     */
    public Tag removeHTMLAttribute (String name) {
        return replaceHTMLAttribute (name, null);
    }
    
    /**
     * Copy this tag, setting an HTML attribute's value to TRUE.
     * @param name Name of HTML attribute (e.g. "HREF").  Doesn't have to be
     * converted with toHTMLAttributeName(). 
     * @return copy of this tag with named attribute set to TRUE.  The copy is 
     * a region of a fresh page containing only the tag. 
     */
    public Tag replaceHTMLAttribute (String name) {
        return replaceHTMLAttribute (name, TRUE);
    }
    
    /**
     * Copy this tag, setting an HTML attribute's value.
     * @param name Name of HTML attribute (e.g. "HREF").  Doesn't have to be
     * converted with toHTMLAttributeName(). 
     * @param value New value for the attribute
     * @return copy of this tag with named attribute set to value.  
     * The copy is 
     * a region of a fresh page containing only the tag. 
     */
    public Tag replaceHTMLAttribute (String name, String value) {
        name = toHTMLAttributeName (name);
        
        if (!startTag)
            return this; // illegal!
        
        StringBuffer newstr = new StringBuffer ();
        String[] newattrs = null;
        
        newstr.append ('<');
        newstr.append (tagName);

        boolean foundit = false;
        
        int len = htmlAttributes.length;
        for (int i=0; i < len; ++i) {
            String attrName = htmlAttributes[i];
            String attrVal;
            
            // FIX: entity-encode attrVal
            if (attrName == name) {
                newattrs = htmlAttributes;
                foundit = true;
                if (value == null)
                    continue;

                attrVal = value;
            }
            else
                attrVal = getLabel (attrName);
            
            newstr.append (' ');
            newstr.append (attrName);
            if (attrVal != TRUE) {
                newstr.append ('=');
                if (attrVal.indexOf ('"') == -1) {
                    newstr.append ('"');
                    newstr.append (attrVal);
                    newstr.append ('"');
                }
                else {
                    newstr.append ('\'');
                    newstr.append (attrVal);
                    newstr.append ('\'');
                }
            }
        }
        if (!foundit && value != null) {
            // add new attribute at end
            newstr.append (' ');
            newstr.append (name);
            if (value != name) {
                newstr.append ('=');
                if (value.indexOf ('"') == -1) {
                    newstr.append ('"');
                    newstr.append (value);
                    newstr.append ('"');
                }
                else {
                    newstr.append ('\'');
                    newstr.append (value);
                    newstr.append ('\'');
                }
            }

            // append name to list of attribute names
            newattrs = new String[len + 1];
            System.arraycopy (htmlAttributes, 0, newattrs, 0, len);
            newattrs[len] = name;
        }
        
        newstr.append ('>');

        Tag newTag = new Tag (new Page (newstr.toString()), 0, 
                              newstr.length(), tagName, startTag);
        newTag.names = names;
        newTag.htmlAttributes = newattrs;
        newTag.setLabel (name, value);
        
        return newTag;
    }

    /**
     * Commonly useful tag names.
     * Derived from <a href="http://www.sandia.gov/sci_compute/elements.html">HTML Elements</a> 
     * at Sandia National Labs. 
     */

    public static final String A = "a".intern();
    public static final String ABBREV = "abbrev".intern();
    public static final String ACRONYM = "acronym".intern();
    public static final String ADDRESS = "address".intern();    
    public static final String APPLET = "applet".intern();
    public static final String AREA = "area".intern();
    public static final String B = "b".intern();
    public static final String BASE = "base".intern();
    public static final String BASEFONT = "basefont".intern();
    public static final String BDO = "bdo".intern();
    public static final String BGSOUND = "bgsound".intern();
    public static final String BIG = "big".intern();
    public static final String BLINK = "blink".intern();
    public static final String BLOCKQUOTE = "blockquote".intern();
    public static final String BODY = "body".intern();
    public static final String BR = "br".intern();
    public static final String CAPTION = "caption".intern();
    public static final String CENTER = "center".intern();
    public static final String CITE = "cite".intern();
    public static final String CODE = "code".intern();
    public static final String COL = "col".intern();
    public static final String COLGROUP = "colgroup".intern();
    public static final String COMMENT = "!".intern();
    public static final String DD = "dd".intern();
    public static final String DEL = "del".intern();
    public static final String DFN = "dfn".intern();
    public static final String DIR = "dir".intern();
    public static final String DIV = "div".intern();
    public static final String DL = "dd".intern();    
    public static final String DT = "dt".intern();
    public static final String EM = "em".intern();
    public static final String EMBED = "embed".intern();
    public static final String FONT = "font".intern();
    public static final String FRAME = "frame".intern();
    public static final String FRAMESET = "frameset".intern();
    public static final String FORM = "form".intern();
    public static final String H1 = "h1".intern();
    public static final String H2 = "h2".intern();
    public static final String H3 = "h3".intern();
    public static final String H4 = "h4".intern();
    public static final String H5 = "h5".intern();
    public static final String H6 = "h6".intern();
    public static final String HEAD = "head".intern();
    public static final String HR = "hr".intern();
    public static final String HTML = "html".intern();
    public static final String I = "i".intern();
    public static final String IMG = "img".intern();
    public static final String INPUT = "input".intern();
    public static final String ISINDEX = "isindex".intern();
    public static final String KBD = "kbd".intern();
    public static final String LI = "li".intern();
    public static final String LINK = "link".intern();
    public static final String LISTING = "listing".intern();
    public static final String MAP = "map".intern();
    public static final String MARQUEE = "marquee".intern();
    public static final String MENU = "menu".intern();
    public static final String META = "meta".intern();
    public static final String NEXTID = "nextid".intern();
    public static final String NOBR = "nobr".intern();
    public static final String NOEMBED = "noembed".intern();
    public static final String NOFRAMES = "noframes".intern();
    public static final String OBJECT = "object".intern();
    public static final String OL = "ol".intern();
    public static final String OPTION = "option".intern();
    public static final String P = "p".intern();
    public static final String PARAM = "param".intern();
    public static final String PLAINTEXT = "plaintext".intern();
    public static final String PRE = "pre".intern();
    public static final String SAMP = "samp".intern();
    public static final String SCRIPT = "script".intern();
    public static final String SELECT = "select".intern();
    public static final String SMALL = "small".intern();
    public static final String SPACER = "spacer".intern();
    public static final String STRIKE = "strike".intern();
    public static final String STRONG = "strong".intern();
    public static final String STYLE = "style".intern();
    public static final String SUB = "sub".intern();
    public static final String SUP = "sup".intern();
    public static final String TABLE = "table".intern();
    public static final String TD = "td".intern();
    public static final String TEXTAREA = "textarea".intern();
    public static final String TH = "th".intern();
    public static final String TITLE = "title".intern();
    public static final String TR = "tr".intern();
    public static final String TT = "tt".intern();
    public static final String U = "u".intern();
    public static final String UL = "ul".intern();
    public static final String VAR = "var".intern();
    public static final String WBR = "wbr".intern();
    public static final String XMP = "xmp".intern();
    
    /**
     * Length of longest tag name.
     */
    public static int MAX_LENGTH = 10;      // longest tag name is BLOCKQUOTE
}