zscript.java

ZK 基础介绍 功能操作 模块 结合数据库操作

/* ZScript.java

{{IS_NOTE
	Purpose:
		
	Description:
		
	History:
		Thu Jun  2 10:46:03     2005, Created by tomyeh
}}IS_NOTE

Copyright (C) 2005 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
	This program is distributed under GPL Version 2.0 in the hope that
	it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.zk.ui.metainfo;

import java.net.URL;

import org.zkoss.lang.D;
import org.zkoss.util.logging.Log;
import org.zkoss.util.resource.ResourceCache;
import org.zkoss.util.resource.ContentLoader;
import org.zkoss.util.resource.Locator;

import org.zkoss.zk.ui.Page;
import org.zkoss.zk.ui.Component;
import org.zkoss.zk.ui.Executions;
import org.zkoss.zk.ui.UiException;
import org.zkoss.zk.ui.util.Condition;
import org.zkoss.zk.ui.util.ConditionImpl;
import org.zkoss.zk.xel.ExValue;
import org.zkoss.zk.xel.impl.EvaluatorRef;
import org.zkoss.zk.scripting.Interpreters;

/**
 * Represents a zscript element.
 *
 * @author tomyeh
 */
public class ZScript extends EvalRefStub 
implements Condition, java.io.Serializable {
	private static final Log log = Log.lookup(ZScript.class);

	private String _zslang;
	private final String _cnt;
	/** An URL, an ExValue. */
	private final Object _url;
	private final Locator _locator;
	private final ConditionImpl _cond;
	private boolean _deferred;

	/** Parses the content into a {@link ZScript} instance.
	 *
	 * <p>This method assumes the content is in the following format:<br/>
	 * <code>lang:codes</code><br/>
	 * <code>codes</code>
	 *
	 * <p>For example, "javascript:var m = 0;" returns "javascript", while
	 * "var m = 0;" returns null.
	 *
	 * <p>Note: if the language doesn't exist, null is returned.
	 * Reason: the above syntax may be conflict with some scripting languages.
	 *
	 * <p>Note: no space is allowed.
	 *
	 * @param content the content of zscript codes
	 * @since 3.0.0
	 */
	public static final ZScript parseContent(String content) {
		final int len = content != null ? content.length(): 0;
		for (int j = 0; j < len; ++j) {
			final char cc = content.charAt(j);
			if (cc == ':') {
				if (j > 0) {
					final String zslang = content.substring(0, j);
					if (Interpreters.exists(zslang)) {
						return new ZScript(
							null, zslang, content.substring(j + 1), null);
					} else {
						log.warning("Ignored: unknown scripting language, "+zslang);
					}
				}
				break;
			} if (!Interpreters.isLegalName(cc)) {
				break; //done
			}
		}
		return new ZScript(null, null, content, null);
	}

	/** Creates a zscript object with the content directly.
	 *
	 * @param evalr the evaluator reference. It is required if cond is not null.
	 * @param zslang the scripting language. If null, it is the same as
	 * {@link Page#getZScriptLanguage}.
	 * @param content the zscript content
	 * @since 3.0.0
	 */
	public ZScript(EvaluatorRef evalr, String zslang, String content, ConditionImpl cond) {
		_evalr = evalr;
		_zslang = zslang;
		_cnt = content != null ? content: "";
		_url = null;
		_locator = null;
		_cond = cond;
	}
	/** Create a zscript object with an URL that is used to load the content.
	 *
	 * @param evalr the evaluator reference. It is required if cond is not null.
	 * @param url the URL to load the content of zscript.
	 * @since 3.0.0
	 */
	public ZScript(EvaluatorRef evalr, String zslang, URL url, ConditionImpl cond) {
		if (url == null)
			throw new IllegalArgumentException("null url");

		//TODO: use url's extension to determine zslang
		_evalr = evalr;
		_zslang = zslang;
		_url = url;
		_cnt = null;
		_locator = null;
		_cond = cond;
	}
	/** Constructs a {@link ZScript} with an URL, which might contain an EL
	 * expression.
	 *
	 * @param evalr the evaluator reference.
	 * It is required if cond is not null or url contains EL expression.
	 * @param url the URL. It may contain XEL expressions.
	 * @param locator the locator used to locate the zscript file
	 */
	public ZScript(EvaluatorRef evalr, String zslang, String url, ConditionImpl cond, Locator locator) {
		if (url == null || locator == null)
			throw new IllegalArgumentException("null");

		//TODO: use url's extension to determine zslang
		_evalr = evalr;
		_zslang = zslang;
		_url = new ExValue(url, String.class);
		_cnt = null;
		_locator = locator;
		_cond = cond;
	}

	/** Returns the evaluator reference, or null if not available.
	 */
	/*package*/ EvaluatorRef getEvaluatorRef() {
		return _evalr;
	}

	/** Returns the scripting language, or null if the default scripting language
	 * is preferred.
	 */
	public String getLanguage() {
		return _zslang;
	}
	/** Sets the scripting language.
	 *
	 * @param zslang the scripting language. If null, the default scripting
	 * language is assume.
	 */
	public void setLanguage(String zslang) {
		_zslang = zslang;
	}

	/** Returns the raw content.
	 * It is the content specified in the contructor
	 * ({@link #ZScript(EvaluatorRef, String, String, ConditionImpl)}.
	 * If URL is specified in the contructor, null is returned.
	 *
	 * <p>On the other hand, {@link #getContent} will load the content
	 * automatically if URL is specified.
	 *
	 * @return the raw content specified in the contructor, or null
	 * if URL is specified instead.
	 */
	public String getRawContent() {
		return _cnt;
	}
	/** Returns the content of zscript.
	 * If URL is specified, this method loads the content from it.
	 * If URL is an EL expression, it will be evaluated first.
	 *
	 * <p>Note: before evaluating the returned script, you have to invoke
	 * {@link #isEffective(Component)} or {@link #isEffective(Page)} first.
	 *
	 * @param page the page when this zscript is interpreted.
	 * Used only if this object is contructed with {@link #ZScript(EvaluatorRef, String, String, ConditionImpl, Locator)}.
	 * @param comp the component when this zscript is interpreted.
	 * Used only if this object is contructed with {@link #ZScript(EvaluatorRef, String, String, ConditionImpl, Locator)}.
	 * @exception UiException if faied to load the content
	 */
	public String getContent(Page page, Component comp) {
		if (_cnt != null)
			return _cnt;

		final URL url;
		if (_url instanceof ExValue) {
			final String s = (String)(comp != null ? 
				((ExValue)_url).getValue(_evalr, comp):
				((ExValue)_url).getValue(_evalr, page));
			if (s == null || s.length() == 0)
				throw new UiException("The zscript URL, "+_url+", is evaluated to \""+s+'"');
			url = _locator.getResource(s);
			if (url == null)
				throw new UiException("File not found: "+s+" (evaluated from "+_url+')');
				//note: we don't throw FileNotFoundException since Tomcat 'eats' it
		} else {
			url = (URL)_url;
		}

		final Object o = getCache().get(url);
			//It is OK to use cache here even if script might be located, say,
			//at a database. Reason: it is Locator's job to implement
			//the relevant function for URL (including lastModified).
		if (o == null)
			throw new UiException("File not found: "+_url);
			//note: we don't throw FileNotFoundException since Tomcat 'eats' it
		if (!(o instanceof String))
			throw new UiException("Illegal file type: "+o.getClass());
		return (String)o;
	}

	/** Returns whether the evaluation of the zscript shall be deferred.
	 */
	public boolean isDeferred() {
		return _deferred;
	}
	/** Sets whether the evaluation of the zscript shall be deferred.
	 * <p>Default: false.
	 */
	public void setDeferred(boolean deferred) {
		_deferred = deferred;
	}

	//Condition//
	public boolean isEffective(Component comp) {
		return _cond == null || _cond.isEffective(_evalr, comp);
	}
	public boolean isEffective(Page page) {
		return _cond == null || _cond.isEffective(_evalr, page);
	}

	//Object//
	public String toString() {
		final StringBuffer sb = new StringBuffer(40).append("[zscript: ");
		if (_url != null) {
			sb.append(_url);
		} else {
			final int len = _cnt.length();
			if (len > 20) {
				sb.append(_cnt.substring(0, 16)).append("...");
			} else {
				sb.append(_cnt);
			}
		}
		return sb.append(']').toString();
	}

	private static ResourceCache _cache;
	private static final ResourceCache getCache() {
		if (_cache == null) {
			synchronized (ZScript.class) {
				if (_cache == null) {
					final ResourceCache cache
						= new ResourceCache(new ContentLoader());
					cache.setMaxSize(512);
					cache.setLifetime(60*60*1000); //1hr
					_cache = cache;
				}
			}
		}
		return _cache;
	}
}