org.ini4j.spi.ServiceFinder Maven / Gradle / Ivy
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/*
* Copyright 2005,2009 Ivan SZKIBA
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.ini4j.spi;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
/**
* JDK JAR Services API alap� service keres� oszt�ly.
*
* @author Szkiba Iv�n
* @version $Name: $
*/
final class ServiceFinder
{
private static final String SERVICES_PATH = "META-INF/services/";
private ServiceFinder()
{
}
/**
* Service objektum keres�s �s p�ld�nyos�t�s
*
* a JDK JAR specifik�ci�ban defini�lt Services API-nak
* megfelel�en service oszt�ly keres�s, majd pedig p�ld�ny k�pz�s a context
* ClassLoader seg�ts�g�vel.
* Az implement�l� oszt�ly n�v keres�se a serviceId nev�
* system property vizsg�lat�val kezd�dik. Amennyiben nincs ilyen
* property, �gy a keres�s a
* /META-INF/services/serviceId nev� file tartalm�val
* folytat�dik. Amennyiben nincs ilyen nev� file, �gy a param�terk�nt �tadott
* defaultService lesz az oszt�ly neve.
* A fenti keres�st k�vet�en t�rt�nik a p�ld�ny k�pz�s. A visszat�r�si
* �rt�k mindig egy val�di objektum, l�v�n minden hiba exception-t gener�l.
* @param type
* @param clazz keresett oszt�ly/service neve
* @throws IllegalArgumentException keres�si vagy p�ld�nyos�t�si hiba eset�n
* @return a keresett oszt�ly implement�l� objektum
*/
static T findService(Class clazz)
{
try
{
// ez a cast nem lenne szükséges, de úgy a ClassCastException csak a hívónál jön...
return clazz.cast(findServiceClass(clazz).newInstance());
}
catch (Exception x)
{
throw (IllegalArgumentException) new IllegalArgumentException("Provider " + clazz.getName() + " could not be instantiated: " + x)
.initCause(x);
}
}
@SuppressWarnings(Warnings.UNCHECKED)
static Class findServiceClass(Class clazz) throws IllegalArgumentException
{
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
String serviceClassName = findServiceClassName(clazz.getName());
Class ret = clazz;
if (serviceClassName != null)
{
try
{
ret = (Class) ((classLoader == null) ? Class.forName(serviceClassName) : classLoader.loadClass(serviceClassName));
}
catch (ClassNotFoundException x)
{
throw (IllegalArgumentException) new IllegalArgumentException("Provider " + serviceClassName + " not found").initCause(x);
}
}
return ret;
}
static String findServiceClassName(String serviceId) throws IllegalArgumentException
{
String serviceClassName = null;
// Use the system property first
try
{
String systemProp = System.getProperty(serviceId);
if (systemProp != null)
{
serviceClassName = systemProp;
}
}
catch (SecurityException x)
{
assert true;
}
if (serviceClassName == null)
{
serviceClassName = loadLine(SERVICES_PATH + serviceId);
}
return serviceClassName;
}
private static String loadLine(String servicePath)
{
String ret = null;
// try to find services in CLASSPATH
try
{
InputStream is = null;
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (classLoader == null)
{
is = ClassLoader.getSystemResourceAsStream(servicePath);
}
else
{
is = classLoader.getResourceAsStream(servicePath);
}
if (is != null)
{
BufferedReader rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));
String line = rd.readLine();
rd.close();
if (line != null)
{
line = line.trim();
if (line.length() != 0)
{
ret = line.split("\\s|#")[0];
}
}
}
}
catch (Exception x)
{
assert true;
}
return ret;
}
}