header.java

非常接近C/S操作方式的Java Ajax框架－ZK 用ZK框架使你的B/S应用程序更漂亮更易操作。 官网：www.zkoss.org

/* Header.java

{{IS_NOTE
	Purpose:
		
	Description:
		
	History:
		Thu Sep 14 22:02:29     2006, Created by tomyeh
}}IS_NOTE

Copyright (C) 2006 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
}}IS_RIGHT
*/
package org.zkoss.zk.ui.metainfo;

import java.util.Iterator;
import java.util.Map;
import java.util.List;
import java.util.LinkedList;
import java.util.Collections;

import org.zkoss.xml.HTMLs;
import org.zkoss.zk.ui.Page;
import org.zkoss.zk.ui.Executions;

/**
 * Represents a header element, such as <link> and <meta>.
 * They are usually represented as directives in ZUML.
 * For example, the link and meta directives represent <link>
 * and <meta> HTML tags, respectively.
 *
 * @author tomyeh
 */
public class Header {
	private final String _name;
	private final List _attrs;

	/** Constructor.
	 *
	 * <p>Note: it detects the href attribute (from the attrs argument), and
	 * encodes it with {@link Executions#encodeURL}.
	 *
	 * @param name the tag name, such as link (never null or empty).
	 * @param attrs a map of (String, String) attributes.
	 */
	public Header(String name, Map attrs) {
		if (name == null || name.length() == 0)
			throw new IllegalArgumentException("empty");

		_name = name;
		if (attrs == null || attrs.isEmpty()) {
			_attrs = Collections.EMPTY_LIST;
		} else {
			_attrs = new LinkedList();
			for (Iterator it = attrs.entrySet().iterator(); it.hasNext();) {
				final Map.Entry me = (Map.Entry)it.next();
				final Object nm = me.getKey(), val = me.getValue();
				if (!(nm instanceof String))
					throw new IllegalArgumentException("String is expected, not "+nm);
				if (!(val instanceof String))
					throw new IllegalArgumentException("String is expected, not "+val);

				_attrs.add(new String[] {(String)nm, (String)val});
			}
		}
	}
	/** Returns the tag name of this header element.
	 */
	public String getName() {
		return _name;
	}

	/** Returns as HTML tag(s) representing this header element.
	 *
	 * @param page the page containing this header element.
	 * It is used to evaluate EL expression, if any, contained in the value.
	 */
	public String toHTML(Page page) {
		final StringBuffer sb = new StringBuffer(128)
			.append('<').append(_name);

		for (Iterator it = _attrs.iterator(); it.hasNext();) {
			final String[] p = (String[])it.next();
			String nm = p[0];
			String val = (String)Executions.evaluate(page, p[1], String.class);

			if (val == null || val.length() == 0) {
				sb.append(' ').append(nm).append("=\"\"");
			} else {
				if ("href".equals(nm)) val = Executions.encodeURL(val);
				HTMLs.appendAttribute(sb, nm, val);
			}
		}

		return sb.append("/>").toString();
	}
}