org.apache.openjpa.lib.util.JavaVersions 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 org.apache.openjpa.lib.util;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.security.AccessController;
/**
* Utilities for dealing with different Java specification versions.
*
* @author Abe White
* @author Pinaki Poddar
*
*/
public class JavaVersions {
/**
* Java version; one of 2, 3, 4, 5, 6, or 7.
*/
public static final int VERSION;
private static final Class[] EMPTY_CLASSES = new Class[0];
static {
String specVersion = AccessController.doPrivileged(
J2DoPrivHelper.getPropertyAction("java.specification.version"));
if ("1.2".equals(specVersion))
VERSION = 2;
else if ("1.3".equals(specVersion))
VERSION = 3;
else if ("1.4".equals(specVersion))
VERSION = 4;
else if ("1.5".equals(specVersion))
VERSION = 5;
else if ("1.6".equals(specVersion))
VERSION = 6;
else
VERSION = 7; // maybe someday...
}
/**
* Collects the parameterized type declarations for a given field.
*/
public static Class[] getParameterizedTypes(Field f) {
try {
return collectParameterizedTypes(f.getGenericType(), f.getType());
} catch (Exception e) {
return EMPTY_CLASSES;
}
}
/**
* Collects the parameterized return type declarations for a given method.
*/
public static Class[] getParameterizedTypes(Method meth) {
try {
return collectParameterizedTypes(meth.getGenericReturnType(), meth.getReturnType());
} catch (Exception e) {
return EMPTY_CLASSES;
}
}
/**
* Return all parameterized classes for the given type.
*/
private static Class[] collectParameterizedTypes(Type type, Class cls) throws Exception {
if (type instanceof ParameterizedType) {
Type[] args = ((ParameterizedType)type).getActualTypeArguments();
Class[] clss = new Class[args.length];
for (int i = 0; i < args.length; i++) {
Class c = extractClass(args[i]);
if (c == null) {
return EMPTY_CLASSES;
}
clss[i] = c;
}
return clss;
} else if (cls.getSuperclass() != Object.class) {
return collectParameterizedTypes(cls.getGenericSuperclass(), cls.getSuperclass());
} else {
return EMPTY_CLASSES;
}
}
/**
* Extracts the class from the given argument, if possible. Null otherwise.
*/
static Class extractClass(Type type) throws Exception {
if (type instanceof Class) {
return (Class)type;
} else if (type instanceof ParameterizedType) {
return extractClass(((ParameterizedType)type).getRawType());
}
return null;
}
}