htmlscrubber.java

HTML解释器JAVA源码

/*
 * HtmlScrubber.java -- cleans up HTML document tree.  
 * Copyright (C) 1999 Quiotix Corporation.  
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as 
 * published by the Free Software Foundation.  
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License (http://www.gnu.org/copyleft/gpl.txt)
 * for more details.
 */

package com.quiotix.html.parser;
import java.io.*;
import java.util.*;

/** 
 * HtmlScrubber is a Visitor which walks an HtmlDocument and cleans it up.
 * It can change tags and tag attributes to uppercase or lowercase, strip
 * out unnecessary quotes from attribute values, and strip trailing spaces
 * before a newline.
 *
 * @author Brian Goetz, Quiotix
 * Additional contributions by: Thorsten Weber
 */

public class HtmlScrubber extends HtmlVisitor {

  public static final int TAGS_UPCASE     = 1;
  public static final int TAGS_DOWNCASE   = 2;
  public static final int ATTR_UPCASE     = 4;
  public static final int ATTR_DOWNCASE   = 8;
  public static final int STRIP_QUOTES    = 16;
  public static final int TRIM_SPACES     = 32;
  public static final int DEFAULT_OPTIONS = 
    TAGS_DOWNCASE | ATTR_DOWNCASE | STRIP_QUOTES;

  protected int flags;
  protected HtmlDocument.HtmlElement previousElement;
  protected boolean inPreBlock;

  /** Create an HtmlScrubber with the default options (downcase tags and
   * tag attributes, strip out unnecessary quotes.) 
   */
  public HtmlScrubber() {
    this(DEFAULT_OPTIONS);
  };

  /** Create an HtmlScrubber with the desired set of options.
   * @param flags A bitmask representing the desired scrubbing options
   */

  public HtmlScrubber(int flags) {
    this.flags = flags;
  };

  private static boolean safeToUnquote(String qs) {
    int l, upperCount=0, lowerCount=0, idCount=0;
        
    for (int i=1; i < qs.length()-1; i++) {
      char c = qs.charAt(i);
      if (Character.isUnicodeIdentifierPart(c))
        ++idCount;
      if (Character.isUpperCase(c))
        ++upperCount;
      else if (Character.isLowerCase(c))
        ++lowerCount;
    };
    return (qs.length()-2 > 0
            && (qs.length()-2 == idCount 
                && (upperCount == 0 || lowerCount == 0)));
  };

  public void start() {
    previousElement = null;
    inPreBlock = false;
  };

  public void visit(HtmlDocument.Tag t) {
    if ((flags & TAGS_UPCASE) != 0) 
      t.tagName = t.tagName.toUpperCase();
    else if ((flags & TAGS_DOWNCASE) != 0) 
      t.tagName = t.tagName.toLowerCase();
    for (Enumeration ae=t.attributeList.attributes.elements();
         ae.hasMoreElements(); ) {
      HtmlDocument.Attribute a = (HtmlDocument.Attribute) ae.nextElement(); 
      if ((flags & ATTR_UPCASE) != 0) 
        a.name = a.name.toUpperCase();
      else if ((flags & ATTR_DOWNCASE) != 0) 
        a.name = a.name.toLowerCase();
      if (((flags & STRIP_QUOTES) != 0) 
          && a.hasValue
          && ((a.value.charAt(0) == '\'' 
               && a.value.charAt(a.value.length()-1) == '\'')
              || (a.value.charAt(0) == '\"' 
                  && a.value.charAt(a.value.length()-1) == '\"'))
          && safeToUnquote(a.value)) {
        a.value = a.value.substring(1, a.value.length()-1);
      };
    };

    previousElement = t;
  }

  public void visit(HtmlDocument.EndTag t) {
    if ((flags & TAGS_UPCASE) != 0) 
      t.tagName = t.tagName.toUpperCase();
    else if ((flags & TAGS_DOWNCASE) != 0) 
      t.tagName = t.tagName.toLowerCase();

    previousElement = t;
  }

  public void visit(HtmlDocument.Text t)        { 
    if (((flags & TRIM_SPACES) != 0) 
        && !inPreBlock
        && (previousElement instanceof HtmlDocument.Newline
            || previousElement instanceof HtmlDocument.Tag
            || previousElement instanceof HtmlDocument.EndTag
            || previousElement instanceof HtmlDocument.Comment)) {
      int i; 
      for (i=0; i<t.text.length(); i++) 
        if (t.text.charAt(i) != ' ' 
            && t.text.charAt(i) != '\t')
          break;
      if (i > 0) 
        t.text = t.text.substring(i);
    };
    previousElement = t; 
  }

  public void visit(HtmlDocument.Comment c)     { previousElement = c; }
  public void visit(HtmlDocument.Newline n)     { previousElement = n; }
  public void visit(HtmlDocument.Annotation a)  { previousElement = a; }
  public void visit(HtmlDocument.TagBlock bl) {
    if (bl.startTag.tagName.equalsIgnoreCase("PRE")
        || bl.startTag.tagName.equalsIgnoreCase("SCRIPT")
        || bl.startTag.tagName.equalsIgnoreCase("STYLE")) {
      inPreBlock = true;
      super.visit(bl);
      inPreBlock = false;
    }
    else
      super.visit(bl);
  }
}