zcommon/src/main/java/org/zkoss/lang/Library.java
/* Library.java
Purpose:
Description:
History:
Fri Aug 1 09:06:36 2008, Created by tomyeh
Copyright (C) 2008 Potix Corporation. All Rights Reserved.
{{IS_RIGHT
This program is distributed under LGPL Version 2.1 in the hope that
it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.lang;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Represent the scope of ZK libraries.
* Unlike {@link System}, the scope of {@link Library} depends how
* ZK libraries are installed.
* If they are installed in WEB-INF/lib of a ZK application,
* the scope is the application. In other words, the library properties
* ({@link #setProperty}) are shared by the application only.
*
* <p>On the other hand, if ZK libraries are installed in a folder
* shared by all applications, the library properties are shared
* by all applications.
*
* @author tomyeh
* @since 3.0.7
*/
public class Library {
private static final Logger log = LoggerFactory.getLogger(Library.class);
//ZK-3823: Using the ConcurrentHashMap to substitute synchronized HashMap can avoid the thread lock issue.
//Enhance the performance of the code.
private static final Map<String, List<String>> _props = new ConcurrentHashMap<String, List<String>>();
private Library() {}
/** Returns the library property indicated by the specified key.
* If no such library property, this method will call
* {@link System#getProperty} to look for a system property.
*
* <p>The library property is shared by Java codes that access
* the same set of ZK libraries, since it is actually
* a static member of this class. Thus, if ZK libraries (including
* this class) are installed in WEB-INF/lib of an application,
* the library properties are accessible only in the application.
*
* <p>Note: unlike {@link System#getProperty}, this method won't
* throw SecurityException.
*
* @return the string value of the library property, or the system
* property, or null if no such property.
* @see #setProperty
*/
public static String getProperty(String key) {
final String v;
List<String> valList = _props.get(key);
if (valList != null && valList.size() > 0)
v = valList.get(0);
else
v = null;
try {
//Unlike System.getProperty, we make the inocation as safe as possible
return v != null || key == null || key.length() == 0 ?
v: System.getProperty(key);
} catch (SecurityException ex) {
return null;
}
}
/** Returns the library property indicated by the specified key.
* If no such library property, this method will call
* {@link System#getProperty} to look for a system property.
*
* <p>Note: unlike {@link System#getProperty}, this method won't
* throw SecurityException.
*
* @param key the name of the library property
* @param def a default value.
* @exception NullPointerException if key is null
* @exception IllegalArgumentException if key is empty
*/
public static String getProperty(String key, String def) {
final String v;
List<String> valList = _props.get(key);
if (valList != null && valList.size() > 0)
v = valList.get(0);
else
v = null;
try {
return v != null ? v: System.getProperty(key, def);
} catch (SecurityException ex) {
return def;
}
}
/** Sets the library property indicated by the specified key.
* @see #getProperty
* @exception NullPointerException if key is null
* @exception IllegalArgumentException if key is empty
* @return the previous value of the library property, or null if
* it did not have one.
*/
public static String setProperty(String key, String value) {
if (key == null) throw new NullPointerException();
if (key.length() == 0) throw new IllegalArgumentException();
List<String> vals = new LinkedList<String>();
vals.add(value);
List<String> prev = _props.put(key, vals);
return prev != null && prev.size() > 0 ? prev.get(0) : null;
}
/** Parses the property value to an integer.
* If the specified value is not an integer, the default value is returned
* (and a warning is logged).
* @param defVal the default value
* @since 3.6.1
*/
public static int getIntProperty(String key, int defVal) {
final String val = getProperty(key);
if (val != null) {
try {
return Integer.parseInt(val);
} catch (Throwable t) {
log.warn("Failed to parse " + key + ": not an integer, " + val);
}
}
return defVal;
}
/** Add a library property indicated by the specified key.
* @see #getProperties
* @exception NullPointerException if key is null
* @exception IllegalArgumentException if key is empty
* @return the previous value of the library properties, or null if
* it did not have any.
*/
public static List<String> addProperty(String key, String value) {
if (key == null) throw new NullPointerException();
if (key.length() == 0) throw new IllegalArgumentException();
synchronized (_props) {
List<String> old = _props.get(key);
if (old == null)
old = new LinkedList<String>();
old.add(value);
return _props.put(key, old);
}
}
/** Add library properties indicated by the specified key.
* @see #getProperties
* @exception NullPointerException if key is null
* @exception IllegalArgumentException if key is empty
* @return the previous value of the library properties, or null if
* it did not have any.
*/
public static List<String> addProperties(String key, List<String> values) {
if (key == null) throw new NullPointerException();
if (key.length() == 0) throw new IllegalArgumentException();
synchronized (_props) {
List<String> old = _props.get(key);
if (old == null)
old = new LinkedList<String>();
old.addAll(values);
return _props.put(key, old);
}
}
/** Sets the library properties indicated by the specified key.
* @see #getProperties
* @exception NullPointerException if key is null
* @exception IllegalArgumentException if key is empty
* @return the previous value of the library properties, or null if
* it did not have any.
*/
public static List<String> setProperties(String key, List<String> values) {
if (key == null) throw new NullPointerException();
if (key.length() == 0) throw new IllegalArgumentException();
return _props.put(key, new LinkedList<String>(values));
}
/** Returns the library properties indicated by the specified key.
*
* <p>The library properties is shared by Java codes that access
* the same set of ZK libraries, since it is actually
* a static member of this class. Thus, if ZK libraries (including
* this class) are installed in WEB-INF/lib of an application,
* the library properties are accessible only in the application.
*
* @return the List of values of the library properties,
* or null if no such property.
* @see #setProperties
*/
public static List<String> getProperties(String key) {
return _props.get(key);
}
}