Java/Reflection/Inheritance
Содержание
Class comparator: compare and sort classes and their superclasses.
<source lang="java">
/*
* JCommon : a free general purpose class library for the Java(tm) platform * * * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors. * * Project Info: http://www.jfree.org/jcommon/index.html * * This library is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or * (at your option) any later version. * * This library 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 library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, * USA. * * [Java is a trademark or registered trademark of Sun Microsystems, Inc. * in the United States and other countries.] * * -------------------- * ClassComparator.java * -------------------- * (C)opyright 2003-2005, by Thomas Morgner and Contributors. * * Original Author: Thomas Morgner (taquera@sherito.org); * Contributor(s): David Gilbert (for Object Refinery Limited); * * $Id: ClassComparator.java,v 1.3 2005/10/18 13:24:19 mungady Exp $ * * Changes * ------- * 02-May-2003 : Initial version * */
import java.io.Serializable; import java.util.ruparator; /**
* The class comparator can be used to compare and sort classes and their * superclasses. The comparator is not able to compare classes which have no * relation... * * @author Thomas Morgner */
public class ClassComparator implements Comparator, Serializable {
/** For serialization. */
private static final long serialVersionUID = -5225335361837391120L;
/**
* Defaultconstructor.
*/
public ClassComparator() {
super();
}
/**
* Compares its two arguments for order. Returns a negative integer, zero, or
* a positive integer as the first argument is less than, equal to, or greater
* than the second.
* * <P> * Note: throws ClassCastException if the arguments" types prevent them from * being compared by this Comparator. And IllegalArgumentException if the * classes share no relation. * * The implementor must ensure that sgn(compare(x, y)) == * -sgn(compare(y, x)) * for all x and y. (This implies that * compare(x, y) must throw an exception if and only if * compare(y, x) throws an exception.) * <p> * * The implementor must also ensure that the relation is transitive: * ((compare(x, y)>0) && (compare(y, z)>0)) implies * compare(x, z)>0. * <p> * * Finally, the implementer must ensure that compare(x, y)==0 * implies that sgn(compare(x, z))==sgn(compare(y, z)) for all * z. * <p> * * It is generally the case, but not strictly required that * (compare(x, y)==0) == (x.equals(y)). Generally speaking, any * comparator that violates this condition should clearly indicate this fact. * The recommended language is "Note: this comparator imposes orderings that * are inconsistent with equals." * * @param o1 * the first object to be compared. * @param o2 * the second object to be compared. * @return a negative integer, zero, or a positive integer as the first * argument is less than, equal to, or greater than the second. */ public int compare(final Object o1, final Object o2) { final Class c1 = (Class) o1; final Class c2 = (Class) o2; if (c1.equals(o2)) { return 0; } if (c1.isAssignableFrom(c2)) { return -1; } else { if (!c2.isAssignableFrom(c2)) { throw new IllegalArgumentException("The classes share no relation"); } return 1; } } /** * Checks, whether the given classes are comparable. This method will return * true, if one of the classes is assignable from the other class. * * @param c1 * the first class to compare * @param c2 * the second class to compare * @return true, if the classes share a direct relation, false otherwise. */ public boolean isComparable(final Class c1, final Class c2) { return (c1.isAssignableFrom(c2) || c2.isAssignableFrom(c1)); } } </source>
Find Inherited Field
<source lang="java">
// //$Id: IntrospectionUtil.java 1540 2007-01-19 12:24:10Z janb $ //Copyright 2006 Mort Bay Consulting Pty. Ltd. //------------------------------------------------------------------------ //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. // import java.lang.reflect.Field; import java.lang.reflect.Member; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.util.Arrays; import java.util.List; public class IntrospectionUtil {
protected static Field findInheritedField(Package pack, Class clazz, String fieldName,
Class fieldType, boolean strictType) throws NoSuchFieldException {
if (clazz == null)
throw new NoSuchFieldException("No class");
if (fieldName == null)
throw new NoSuchFieldException("No field name");
try {
Field field = clazz.getDeclaredField(fieldName);
if (isInheritable(pack, field) && isTypeCompatible(fieldType, field.getType(), strictType))
return field;
else
return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), fieldName, fieldType,
strictType);
} catch (NoSuchFieldException e) {
return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), fieldName, fieldType,
strictType);
}
}
public static boolean isInheritable(Package pack, Member member) {
if (pack == null)
return false;
if (member == null)
return false;
int modifiers = member.getModifiers();
if (Modifier.isPublic(modifiers))
return true;
if (Modifier.isProtected(modifiers))
return true;
if (!Modifier.isPrivate(modifiers) && pack.equals(member.getDeclaringClass().getPackage()))
return true;
return false;
}
public static boolean checkParams(Class[] formalParams, Class[] actualParams, boolean strict) {
if (formalParams == null && actualParams == null)
return true;
if (formalParams == null && actualParams != null)
return false;
if (formalParams != null && actualParams == null)
return false;
if (formalParams.length != actualParams.length)
return false;
if (formalParams.length == 0)
return true;
int j = 0;
if (strict) {
while (j < formalParams.length && formalParams[j].equals(actualParams[j]))
j++;
} else {
while ((j < formalParams.length) && (formalParams[j].isAssignableFrom(actualParams[j]))) {
j++;
}
}
if (j != formalParams.length) {
return false;
}
return true;
}
public static boolean isSameSignature(Method methodA, Method methodB) {
if (methodA == null)
return false;
if (methodB == null)
return false;
List parameterTypesA = Arrays.asList(methodA.getParameterTypes());
List parameterTypesB = Arrays.asList(methodB.getParameterTypes());
if (methodA.getName().equals(methodB.getName()) && parameterTypesA.containsAll(parameterTypesB))
return true;
return false;
}
public static boolean isTypeCompatible(Class formalType, Class actualType, boolean strict) {
if (formalType == null && actualType != null)
return false;
if (formalType != null && actualType == null)
return false;
if (formalType == null && actualType == null)
return true;
if (strict)
return formalType.equals(actualType);
else
return formalType.isAssignableFrom(actualType);
}
}
</source>
Find Inherited Method
<source lang="java">
// //$Id: IntrospectionUtil.java 1540 2007-01-19 12:24:10Z janb $ //Copyright 2006 Mort Bay Consulting Pty. Ltd. //------------------------------------------------------------------------ //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. // import java.lang.reflect.Field; import java.lang.reflect.Member; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.util.Arrays; import java.util.List; public class IntrospectionUtil {
protected static Method findInheritedMethod(Package pack, Class clazz, String methodName,
Class[] args, boolean strictArgs) throws NoSuchMethodException {
if (clazz == null)
throw new NoSuchMethodException("No class");
if (methodName == null)
throw new NoSuchMethodException("No method name");
Method method = null;
Method[] methods = clazz.getDeclaredMethods();
for (int i = 0; i < methods.length && method == null; i++) {
if (methods[i].getName().equals(methodName) && isInheritable(pack, methods[i])
&& checkParams(methods[i].getParameterTypes(), args, strictArgs))
method = methods[i];
}
if (method != null) {
return method;
} else
return findInheritedMethod(clazz.getPackage(), clazz.getSuperclass(), methodName, args,
strictArgs);
}
protected static Field findInheritedField(Package pack, Class clazz, String fieldName,
Class fieldType, boolean strictType) throws NoSuchFieldException {
if (clazz == null)
throw new NoSuchFieldException("No class");
if (fieldName == null)
throw new NoSuchFieldException("No field name");
try {
Field field = clazz.getDeclaredField(fieldName);
if (isInheritable(pack, field) && isTypeCompatible(fieldType, field.getType(), strictType))
return field;
else
return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), fieldName, fieldType,
strictType);
} catch (NoSuchFieldException e) {
return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), fieldName, fieldType,
strictType);
}
}
public static boolean isInheritable(Package pack, Member member) {
if (pack == null)
return false;
if (member == null)
return false;
int modifiers = member.getModifiers();
if (Modifier.isPublic(modifiers))
return true;
if (Modifier.isProtected(modifiers))
return true;
if (!Modifier.isPrivate(modifiers) && pack.equals(member.getDeclaringClass().getPackage()))
return true;
return false;
}
public static boolean checkParams(Class[] formalParams, Class[] actualParams, boolean strict) {
if (formalParams == null && actualParams == null)
return true;
if (formalParams == null && actualParams != null)
return false;
if (formalParams != null && actualParams == null)
return false;
if (formalParams.length != actualParams.length)
return false;
if (formalParams.length == 0)
return true;
int j = 0;
if (strict) {
while (j < formalParams.length && formalParams[j].equals(actualParams[j]))
j++;
} else {
while ((j < formalParams.length) && (formalParams[j].isAssignableFrom(actualParams[j]))) {
j++;
}
}
if (j != formalParams.length) {
return false;
}
return true;
}
public static boolean isSameSignature(Method methodA, Method methodB) {
if (methodA == null)
return false;
if (methodB == null)
return false;
List parameterTypesA = Arrays.asList(methodA.getParameterTypes());
List parameterTypesB = Arrays.asList(methodB.getParameterTypes());
if (methodA.getName().equals(methodB.getName()) && parameterTypesA.containsAll(parameterTypesB))
return true;
return false;
}
public static boolean isTypeCompatible(Class formalType, Class actualType, boolean strict) {
if (formalType == null && actualType != null)
return false;
if (formalType != null && actualType == null)
return false;
if (formalType == null && actualType == null)
return true;
if (strict)
return formalType.equals(actualType);
else
return formalType.isAssignableFrom(actualType);
}
}
</source>
Is Inheritable
<source lang="java">
// //$Id: IntrospectionUtil.java 1540 2007-01-19 12:24:10Z janb $ //Copyright 2006 Mort Bay Consulting Pty. Ltd. //------------------------------------------------------------------------ //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. //
import java.lang.reflect.Member; import java.lang.reflect.Modifier; public class Utils {
public static boolean isInheritable(Package pack, Member member) {
if (pack == null)
return false;
if (member == null)
return false;
int modifiers = member.getModifiers();
if (Modifier.isPublic(modifiers))
return true;
if (Modifier.isProtected(modifiers))
return true;
if (!Modifier.isPrivate(modifiers) && pack.equals(member.getDeclaringClass().getPackage()))
return true;
return false;
}
}
</source>
Return a List of super-classes for the given class.
<source lang="java">
import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.List; import java.util.Locale; import java.util.Map; import javax.servlet.http.HttpServletResponse; /*
* Copyright 2005 Joe Walker * * 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. */
/**
* @author Joe Walker [joe at getahead dot ltd dot uk] */
public class Main {
/**
* Return a List of super-classes for the given class.
* @param clazz the class to look up
* @return the List of super-classes in order going up from this one
*/
public static List<Class<?>> getAllSuperclasses(Class<?> clazz)
{
List<Class<?>> classes = new ArrayList<Class<?>>();
Class<?> superclass = clazz.getSuperclass();
while (superclass != null)
{
classes.add(superclass);
superclass = superclass.getSuperclass();
}
return classes;
}
}
</source>
