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* Copyright 2004 The Apache Software Foundation
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*
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package javax.el;
import java.lang.reflect.
Constructor;
import java.io.
InputStream;
import java.io.
File;
import java.io.
FileInputStream;
import java.util.
Properties;
import java.io.
BufferedReader;
import java.io.
InputStreamReader;
class
FactoryFinder {
/**
* Creates an instance of the specified class using the specified
* <code>ClassLoader</code> object.
*
* @exception ELException if the given class could not be found
* or could not be instantiated
*/
private static
Object newInstance(
String className,
ClassLoader classLoader,
Properties properties)
{
try {
Class<?>
spiClass;
if (
classLoader == null) {
spiClass =
Class.
forName(
className);
} else {
spiClass =
classLoader.
loadClass(
className);
}
if (
properties != null) {
Constructor constr = null;
try {
constr =
spiClass.
getConstructor(
Properties.class);
} catch (
Exception ex) {
}
if (
constr != null) {
return
constr.
newInstance(
properties);
}
}
return
spiClass.
newInstance();
} catch (
ClassNotFoundException x) {
throw new
ELException(
"Provider " +
className + " not found",
x);
} catch (
Exception x) {
throw new
ELException(
"Provider " +
className + " could not be instantiated: " +
x,
x);
}
}
/**
* Finds the implementation <code>Class</code> object for the given
* factory name, or if that fails, finds the <code>Class</code> object
* for the given fallback class name. The arguments supplied must be
* used in order. If using the first argument is successful, the second
* one will not be used.
* <P>
* This method is package private so that this code can be shared.
*
* @return the <code>Class</code> object of the specified message factory;
* may not be <code>null</code>
*
* @param factoryId the name of the factory to find, which is
* a system property
* @param fallbackClassName the implementation class name, which is
* to be used only if nothing else
* is found; <code>null</code> to indicate that
* there is no fallback class name
* @exception ELException if there is an error
*/
static
Object find(
String factoryId,
String fallbackClassName,
Properties properties)
{
ClassLoader classLoader;
try {
classLoader =
Thread.
currentThread().
getContextClassLoader();
} catch (
Exception x) {
throw new
ELException(
x.
toString(),
x);
}
String serviceId = "META-INF/services/" +
factoryId;
// try to find services in CLASSPATH
try {
InputStream is=null;
if (
classLoader == null) {
is=
ClassLoader.
getSystemResourceAsStream(
serviceId);
} else {
is=
classLoader.
getResourceAsStream(
serviceId);
}
if(
is!=null ) {
BufferedReader rd =
new
BufferedReader(new
InputStreamReader(
is, "UTF-8"));
String factoryClassName =
rd.
readLine();
rd.
close();
if (
factoryClassName != null &&
! "".
equals(
factoryClassName)) {
return
newInstance(
factoryClassName,
classLoader,
properties);
}
}
} catch(
Exception ex ) {
}
// try to read from $java.home/lib/el.properties
try {
String javah=
System.
getProperty( "java.home" );
String configFile =
javah +
File.
separator +
"lib" +
File.
separator + "el.properties";
File f=new
File(
configFile );
if(
f.
exists()) {
Properties props=new
Properties();
props.
load( new
FileInputStream(
f));
String factoryClassName =
props.
getProperty(
factoryId);
return
newInstance(
factoryClassName,
classLoader,
properties);
}
} catch(
Exception ex ) {
}
// Use the system property
try {
String systemProp =
System.
getProperty(
factoryId );
if(
systemProp!=null) {
return
newInstance(
systemProp,
classLoader,
properties);
}
} catch (
SecurityException se) {
}
if (
fallbackClassName == null) {
throw new
ELException(
"Provider for " +
factoryId + " cannot be found", null);
}
return
newInstance(
fallbackClassName,
classLoader,
properties);
}
}