attributelist.java

java html 解析小程序,文件包很小

/*
 * HTML Parser
 * Copyright (C) 1997 David McNicol
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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
 * file COPYING for more details.
 */

package cvu.html;

import java.util.Hashtable;
import java.util.Vector;
import java.util.Enumeration;

/**
 * This class represents the attribute list of an tag.
 * @see TagToken
 * @author <a href="http://www.strath.ac.uk/~ras97108/">David McNicol</a>
 */
public class AttributeList {

	private Hashtable list;	 // Stores the attributes.

	public AttributeList () {

		// Create a new hashtable to store the attributes.
		list = new Hashtable();
	}

	/**
	 * Returns the number of attributes currently defined.
	 */
	public int size () {
		return list.size();
	}

	/**
	 * Returns the value of the attribute with the specified name.
	 * @param the name of the attribute.
	 */
	public String get (String name) {
		
		// Check the name of the attribute is not null.
		if (name == null) return null;

		// Check that the attribute list is there.
		if (list == null) return null;

		// Return the value associated with the attribute name.
		return (String) list.get(name.toLowerCase());
	}

	/**
	 * Sets the attribute with the specified name to the specified
	 * value. If the attribute already has a value it will be
	 * overwritten.
	 * @param name the name of the attribute.
	 * @param value the new value of the attribute.
	 */
	public void set (String name, String value) {

		// Check that the name is not null.
		if (name == null) return;

		// Replace a null value with an empty string.
		if (value == null) value = "";

		// Return if the list of attributes is not defined.
		if (list == null) return;

		// Otherwise, add the attribute and value to the list.
		list.put(name.toLowerCase(), value);
	}

	/**
	 * Returns true if the specified attribute name exists within
	 * the list.
	 * @param the name of the attribute to check.
	 */
	public boolean exists (String name) {

		// Return false if the name is not null.
		if (name == null) return false;

		// Return false of the list is not defined.
		if (list == null) return false;

		// Check the list to see if the attribute exists.
		return list.containsKey(name.toLowerCase());
	}

	/**
	 * Removes the specified attribute from the list.
	 * @param name the name of the attribue to remove.
	 */
	public void unset (String name) {

		// Return if the attribute name is null.
		if (name == null) return;

		// Return if the attribute list is not defined.
		if (list == null) return;

		// Otherwise, remove the attribute from the list.
		list.remove(name.toLowerCase());
	}

	/**
	 * Returns an enumeration of defined attributes.
	 */
	public Enumeration names () {

		// Check that the attribute table has been defined.
		if (list == null) return null;

		// Return an enumeration of all of the defined attributes.
		return list.keys();
	}

	/**
	 * Returns an attribute with all double quote characters
	 * escaped with a backslash.
	 * @param name the name of the attribute.
	 */
	public String getQuoted (String name) {

		String value;	     // Stores the value of the attribute.
		char[] array;	     // Character array from 'value'.
		StringBuffer quoted; // Stores the quoted version of the value.
		int i;		     // Loop variable.

		// Check the name of the attribute is not null.
		if (name == null) return null;

		// Check that the attribute list is there.
		if (list == null) return null;

		// Get the value of the attribute.
		value = (String) list.get(name.toLowerCase());

		// Return nothing if there is no such attribute.
		if (value == null) return null;

		// Return an empty string if that is what is stored.
		if (value.length() == 0) return "";

		// Convert the value into a character array.
		array = value.toCharArray();

		// Create a new StringBuffer to store the quoted value.
		quoted = new StringBuffer(array.length);

		// Loop round the characters in the array.
		for (i = 0; i < array.length; i++) {

			// Escape any quotation marks.
			if (array[i] == '"') {
				quoted.append("\\\"");
				continue;
			}

			// Escape any additional backslash characters.
			if (array[i] == '\\') {
				quoted.append("\\\\");
				continue;
			}

			// Otherwise append the character without an escape.
			quoted.append(array[i]);
		}

		// Return a string version of the buffer.
		return quoted.toString();
	}

	/**
	 * Returns a string version of the attribute and its value.
	 * @param name the name of the attribute.
	 */
	public String toString (String name) {

		String value; // The value of the attribute.

		// Return an empty string if the name is null.
		if (name == null) return "";

		// Return an empty string if the attribute is not defined.
		if (! exists(name)) return "";

		// Get a quoted version of the value.
		value = getQuoted(name);

		// If the value is null return the attribute name by itself.
		if (value == null) return name;

		// Otherwise return the complete string.
		if (value.length() > 0)
			return name + "=\"" + value + '"';
		else
			return name;
	}

	/**
	 * Returns a string version of the attribute list.
	 */
	public String toString () {

		StringBuffer buffer;  // Stores the string version of the list.
		Enumeration nameList; // Stores a list of attribute names.
		String name;	      // Name of the current attribute.
		String attr;	      // String version of a single attribute.

		// Create a new StringBuffer.
		buffer = new StringBuffer();

		// Get a list of all of the attribute names.
		nameList = names();

		while (nameList.hasMoreElements()) {

			// Get the next attribute name from the list.
			name = (String) nameList.nextElement();

			// Get the string version of the attribute.
			attr = toString(name);

			// Add it to the buffer.
			buffer.append(attr);

			// Add whitespace if there are more attributes.
			if (nameList.hasMoreElements())
				buffer.append(' ');
		}

		// Return a string version of the buffer.
		return buffer.toString();
	}
}