freemarker.ext.jython.JythonVersionAdapterHolder Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 freemarker.ext.jython;
import org.python.core.PySystemState;
import freemarker.template.utility.StringUtil;
/**
* Holds the {@link JythonVersionAdapter} so that it's only initialized when this class is accessed.
* This utilizes that the JVM is required to initialize the fields of a class not earlier than the class is
* first accessed. Furthermore, it utilizes that the JVM guarantees that the objects created as part of the class
* initialization will be visible with their after-initialization state for the threads that access it.
*/
class JythonVersionAdapterHolder {
final static JythonVersionAdapter INSTANCE;
static {
// Note: Only the textual version number is available in Jython 2.0.
int version;
try {
// Although PySystemState.version is present in all versions,
// its type changes, so we must use reflection to get it.
version = StringUtil.versionStringToInt(
PySystemState.class.getField("version").get(null).toString());
} catch (Exception e) {
throw new RuntimeException("Failed to get Jython version: " + e);
}
ClassLoader cl = JythonVersionAdapter.class.getClassLoader();
try {
if (version >= 2005000) {
INSTANCE = (JythonVersionAdapter) cl.loadClass(
"freemarker.ext.jython._Jython25VersionAdapter")
.newInstance();
} else if (version >= 2002000) {
INSTANCE = (JythonVersionAdapter) cl.loadClass(
"freemarker.ext.jython._Jython22VersionAdapter")
.newInstance();
} else {
INSTANCE = (JythonVersionAdapter) cl.loadClass(
"freemarker.ext.jython._Jython20And21VersionAdapter")
.newInstance();
}
} catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {
throw adapterCreationException(e);
}
}
private static RuntimeException adapterCreationException(Exception e) {
return new RuntimeException("Unexpected exception when creating JythonVersionAdapter", e);
}
}