/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Middleware LLC.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*
*/
package org.hibernate.util;
import java.lang.reflect.Constructor;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import org.hibernate.AssertionFailure;
import org.hibernate.MappingException;
import org.hibernate.PropertyNotFoundException;
import org.hibernate.property.BasicPropertyAccessor;
import org.hibernate.property.DirectPropertyAccessor;
import org.hibernate.property.Getter;
import org.hibernate.property.PropertyAccessor;
import org.hibernate.type.PrimitiveType;
import org.hibernate.type.Type;
/**
* Utility class for various reflection operations.
*
* @author Gavin King
* @author Steve Ebersole
*/
public final class ReflectHelper {
//TODO: this dependency is kinda Bad
private static final PropertyAccessor BASIC_PROPERTY_ACCESSOR = new BasicPropertyAccessor();
private static final PropertyAccessor DIRECT_PROPERTY_ACCESSOR = new DirectPropertyAccessor();
public static final Class[] NO_PARAM_SIGNATURE = new Class[0];
public static final Object[] NO_PARAMS = new Object[0];
public static final Class[] SINGLE_OBJECT_PARAM_SIGNATURE = new Class[] { Object.class };
private static final Method OBJECT_EQUALS;
private static final Method OBJECT_HASHCODE;
static {
Method eq;
Method hash;
try {
eq = extractEqualsMethod(Object.class);
hash = extractHashCodeMethod(Object.class);
} catch (Exception e) {
throw new AssertionFailure(
"Could not find Object.equals() or Object.hashCode()",
e);
}
OBJECT_EQUALS = eq;
OBJECT_HASHCODE = hash;
}
/**
* Disallow instantiation of ReflectHelper.
*/
private ReflectHelper() {
}
/**
* Encapsulation of getting hold of a class's {@link Object#equals equals} method.
*
* @param clazz The class from which to extract the equals method.
* @return The equals method reference
* @throws NoSuchMethodException Should indicate an attempt to extract equals method from interface.
*/
public static Method extractEqualsMethod(Class clazz)
throws NoSuchMethodException {
return clazz.getMethod("equals", SINGLE_OBJECT_PARAM_SIGNATURE);
}
/**
* Encapsulation of getting hold of a class's {@link Object#hashCode hashCode} method.
*
* @param clazz The class from which to extract the hashCode method.
* @return The hashCode method reference
* @throws NoSuchMethodException Should indicate an attempt to extract hashCode method from interface.
*/
public static Method extractHashCodeMethod(Class clazz)
throws NoSuchMethodException {
return clazz.getMethod("hashCode", NO_PARAM_SIGNATURE);
}
/**
* Determine if the given class defines an {@link Object#equals} override.
*
* @param clazz The class to check
* @return True if clazz defines an equals override.
*/
public static boolean overridesEquals(Class clazz) {
Method equals;
try {
equals = extractEqualsMethod(clazz);
} catch (NoSuchMethodException nsme) {
return false; //its an interface so we can't really tell anything...
}
return !OBJECT_EQUALS.equals(equals);
}
/**
* Determine if the given class defines a {@link Object#hashCode} override.
*
* @param clazz The class to check
* @return True if clazz defines an hashCode override.
*/
public static boolean overridesHashCode(Class clazz) {
Method hashCode;
try {
hashCode = extractHashCodeMethod(clazz);
} catch (NoSuchMethodException nsme) {
return false; //its an interface so we can't really tell anything...
}
return !OBJECT_HASHCODE.equals(hashCode);
}
/**
* Determine if the given class implements the given interface.
*
* @param clazz The class to check
* @param intf The interface to check it against.
* @return True if the class does implement the interface, false otherwise.
*/
public static boolean implements Interface(Class clazz, Class intf) {
assert intf.isInterface() : "Interface to check was not an interface";
return intf.isAssignableFrom(clazz);
}
/**
* Perform resolution of a class name.
* <p/>
* Here we first check the context classloader, if one, before delegating to
* {@link Class#forName(String, boolean, ClassLoader)} using the caller's classloader
*
* @param name The class name
* @param caller The class from which this call originated (in order to access that class's loader).
* @return The class reference.
* @throws ClassNotFoundException From {@link Class#forName(String, boolean, ClassLoader)}.
*/
public static Class classForName(String name, Class caller)
throws ClassNotFoundException {
try {
ClassLoader contextClassLoader = Thread.currentThread()
.getContextClassLoader();
if (contextClassLoader != null) {
return contextClassLoader.loadClass(name);
}
} catch (Throwable ignore) {
}
return Class.forName(name, true, caller.getClassLoader());
}
/**
* Perform resolution of a class name.
* <p/>
* Same as {@link #classForName(String, Class)} except that here we delegate to
* {@link Class#forName(String)} if the context classloader lookup is unsuccessful.
*
* @param name The class name
* @return The class reference.
* @throws ClassNotFoundException From {@link Class#forName(String)}.
*/
public static Class classForName(String name)
throws ClassNotFoundException {
try {
ClassLoader contextClassLoader = Thread.currentThread()
.getContextClassLoader();
if (contextClassLoader != null) {
return contextClassLoader.loadClass(name);
}
} catch (Throwable ignore) {
}
return Class.forName(name);
}
/**
* Is this member publicly accessible.
* <p/>
* Short-hand for {@link #isPublic(Class, Member)} passing the member + {@link Member#getDeclaringClass()}
*
* @param member The member to check
* @return True if the member is publicly accessible.
*/
public static boolean isPublic(Member member) {
return isPublic(member.getDeclaringClass(), member);
}
/**
* Is this member publicly accessible.
*
* @param clazz The class which defines the member
* @param member The memeber.
* @return True if the member is publicly accessible, false otherwise.
*/
public static boolean isPublic(Class clazz, Member member) {
return Modifier.isPublic(member.getModifiers())
&& Modifier.isPublic(clazz.getModifiers());
}
/**
* Attempt to resolve the specified property type through reflection.
*
* @param className The name of the class owning the property.
* @param name The name of the property.
* @return The type of the property.
* @throws MappingException Indicates we were unable to locate the property.
*/
public static Class reflectedPropertyClass(String className,
String name) throws MappingException {
try {
Class clazz = ReflectHelper.classForName(className);
return getter(clazz, name).getReturnType();
} catch (ClassNotFoundException cnfe) {
throw new MappingException("class " + className
+ " not found while looking for property: " + name,
cnfe);
}
}
private static Getter getter(Class clazz, String name)
throws MappingException {
try {
return BASIC_PROPERTY_ACCESSOR.getGetter(clazz, name);
} catch (PropertyNotFoundException pnfe) {
return DIRECT_PROPERTY_ACCESSOR.getGetter(clazz, name);
}
}
/**
* Directly retrieve the {@link Getter} reference via the {@link BasicPropertyAccessor}.
*
* @param theClass The class owning the property
* @param name The name of the property
* @return The getter.
* @throws MappingException Indicates we were unable to locate the property.
*/
public static Getter getGetter(Class theClass, String name)
throws MappingException {
return BASIC_PROPERTY_ACCESSOR.getGetter(theClass, name);
}
/**
* Resolve a constant to its actual value.
*
* @param name The name
* @return The value
*/
public static Object getConstantValue(String name) {
Class clazz;
try {
clazz = classForName(StringHelper.qualifier(name));
} catch (Throwable t) {
return null;
}
try {
return clazz.getField(StringHelper.unqualify(name)).get(
null);
} catch (Throwable t) {
return null;
}
}
/**
* Retrieve the default (no arg) constructor from the given class.
*
* @param clazz The class for which to retrieve the default ctor.
* @return The default constructor.
* @throws PropertyNotFoundException Indicates there was not publicly accessible, no-arg constructor (todo : why PropertyNotFoundException???)
*/
public static Constructor getDefaultConstructor(Class clazz)
throws PropertyNotFoundException {
if (isAbstractClass(clazz)) {
return null;
}
try {
Constructor constructor = clazz
.getDeclaredConstructor(NO_PARAM_SIGNATURE);
if (!isPublic(clazz, constructor)) {
constructor.setAccessible(true);
}
return constructor;
} catch (NoSuchMethodException nme) {
throw new PropertyNotFoundException(
"Object class ["
+ clazz.getName()
+ "] must declare a default (no-argument) constructor");
}
}
/**
* Determine if the given class is declared abstract.
*
* @param clazz The class to check.
* @return True if the class is abstract, false otherwise.
*/
public static boolean isAbstractClass(Class clazz) {
int modifier = clazz.getModifiers();
return Modifier.isAbstract(modifier)
|| Modifier.isInterface(modifier);
}
/**
* Determine is the given class is declared final.
*
* @param clazz The class to check.
* @return True if the class is final, flase otherwise.
*/
public static boolean isFinalClass(Class clazz) {
return Modifier.isFinal(clazz.getModifiers());
}
/**
* Retrieve a constructor for the given class, with arguments matching the specified Hibernate mapping
* {@link Type types}.
*
* @param clazz The class needing instantiation
* @param types The types representing the required ctor param signature
* @return The matching constructor.
* @throws PropertyNotFoundException Indicates we could not locate an appropriate constructor (todo : again with PropertyNotFoundException???)
*/
public static Constructor getConstructor(Class clazz, Type[] types)
throws PropertyNotFoundException {
final Constructor[] candidates = clazz.getConstructors();
for (int i = 0; i < candidates.length; i++) {
final Constructor constructor = candidates[i];
final Class[] params = constructor.getParameterTypes();
if (params.length == types.length) {
boolean found = true;
for (int j = 0; j < params.length; j++) {
final boolean ok = params[j]
.isAssignableFrom(types[j]
.getReturnedClass())
|| (types[j] instanceof PrimitiveType && params[j] == ((PrimitiveType) types[j])
.getPrimitiveClass());
if (!ok) {
found = false;
break;
}
}
if (found) {
if (!isPublic(clazz, constructor)) {
constructor.setAccessible(true);
}
return constructor;
}
}
}
throw new PropertyNotFoundException(
"no appropriate constructor in class: "
+ clazz.getName());
}
public static Method getMethod(Class clazz, Method method) {
try {
return clazz.getMethod(method.getName(), method
.getParameterTypes());
} catch (Exception e) {
return null;
}
}
}
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