Checked back in for consideration in 1.0

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@136965 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/lang/ClassUtils.java

@@ -0,0 +1,221 @@
+package org.apache.commons.lang;
+
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2002 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Commons", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+/**
+ * A set of static utilities for use with ClassUtils.
+ *
+ * @author  bayard@generationjava.com
+ * @version $Id: ClassUtils.java,v 1.1 2002/08/14 04:51:28 bayard Exp $
+ */
+final public class ClassUtils {
+
+    /**
+     * Create an object from the classname. Must have an empty constructor.
+     *
+     * @param classname String name of the class
+     *
+     * @return Object instance of the class or null
+     */
+    static public Object createObject(String classname) {
+        Class tmpClass = null;
+
+        tmpClass = getClass(classname);
+
+        return createObject(tmpClass);
+    }
+
+    /**
+     * Create an object from a class. 
+     *
+     * @param clss Class object to instantiate
+     *
+     * @return Object instance of the class or null
+     */
+    static public Object createObject(Class clss) {
+
+        try {
+            return clss.newInstance();
+        } catch (IllegalAccessException  iae) {
+            System.err.println("Cant instantiate " + clss.getName() + " because " +
+                   iae.getMessage());
+        } catch (InstantiationException  ie) {
+            System.err.println("Cant instantiate " + clss.getName() + " because " +
+                   ie.getMessage());
+        }
+
+        return null;
+    }
+
+    /**
+     * Is this Class in the CLASSPATH
+     *
+     * @param classname String of the class
+     *
+     * @return boolean exists or not.
+     */
+    static public boolean classExists(String classname) {
+        Class tmpClass = null;
+
+        /* try and load class */
+        try {
+            tmpClass = Class.forName(classname);
+        } catch (ClassNotFoundException cnfe) {
+            return false;
+        } catch (IllegalArgumentException iae) {
+            return false;
+        }
+     
+        return true;   
+    }
+
+    /**
+     * Get the Class object for a classname.
+     *
+     * @param classname String of the class
+     *
+     * @return Class instance for the class.
+     */
+    static public Class getClass(String classname) {
+        Class tmpClass = null;
+
+        /* try an load class */
+        try {
+            tmpClass = Class.forName(classname);
+        } catch (ClassNotFoundException cnfe) {
+            System.out.println("Can't resolve classname " + classname);
+        } catch (IllegalArgumentException iae) {
+            System.err.println("Cant resolve " + tmpClass.getName() + " because " + iae.getMessage());
+        }
+     
+        return tmpClass;   
+    }
+
+    /**
+     * Is this Class object an instance of the class with this name.
+     *
+     * @param clss Class instance
+     * @param inst String name of potential supertype
+     *
+     * @return boolean was it an instanceof
+     */
+    static public boolean classInstanceOf(Class clss, String inst) {
+        if(classImplements(clss,inst)) {
+            return true;
+        } else
+        if(classExtends(clss,inst)) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /**
+     * Does this Class implement an interface with this name.
+     *
+     * @param clss Class instance
+     * @param exts String name of potential interface
+     *
+     * @return boolean was it an implementor
+     */
+    static public boolean classImplements(Class clss, String exts) {
+
+      Class sprcls = clss;
+      Class excls  = getClass(exts);
+
+      while(sprcls != null) {
+        Class[] interfaces = sprcls.getInterfaces();
+
+        for(int i=0;i<interfaces.length;i++) {
+            if(interfaces[i].equals(excls)) {
+                return true;
+            }
+        }
+
+        sprcls = sprcls.getSuperclass();
+      }
+
+      return false;
+    }
+
+    /**
+     * Does this Class extend a superclass with this name.
+     *
+     * @param clss Class instance
+     * @param exts String name of potential superclass
+     *
+     * @return boolean was it a superclass
+     */
+    static public boolean classExtends(Class clss, String exts) {
+        if(clss == null) {
+            return false;
+        }
+        if(clss.getName().equals(exts)) {
+            return true;
+        }
+        Class sprcls = clss.getSuperclass();
+        Class excls = getClass(exts);
+
+//        while(! sprcls.equals(sprcls.getSuperclass()) ) {
+        while( sprcls != null ) {
+            if(sprcls.equals(excls)) {
+                return true;
+            }
+            sprcls = sprcls.getSuperclass();
+        }
+        return false;
+    }
+
+}