Java example source code file (SwingLazyValue.java)

This example Java source code file (SwingLazyValue.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

accessibleobject, class, constructor, exception, gui, method, object, privilegedaction, reflection, security, string, swing, swinglazyvalue, uidefaults, void

The SwingLazyValue.java Java example source code

/*
 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package sun.swing;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.AccessibleObject;
import java.security.AccessController;
import java.security.PrivilegedAction;
import javax.swing.UIDefaults;
import sun.reflect.misc.ReflectUtil;

/**
 * SwingLazyValue is a copy of ProxyLazyValue that does not snapshot the
 * AccessControlContext or use a doPrivileged to resolve the class name.
 * It's intented for use in places in Swing where we need ProxyLazyValue, this
 * should never be used in a place where the developer could supply the
 * arguments.
 *
 */
public class SwingLazyValue implements UIDefaults.LazyValue {
    private String className;
    private String methodName;
    private Object[] args;

    public SwingLazyValue(String c) {
        this(c, (String)null);
    }
    public SwingLazyValue(String c, String m) {
        this(c, m, null);
    }
    public SwingLazyValue(String c, Object[] o) {
        this(c, null, o);
    }
    public SwingLazyValue(String c, String m, Object[] o) {
        className = c;
        methodName = m;
        if (o != null) {
            args = o.clone();
        }
    }

    public Object createValue(final UIDefaults table) {
        try {
            ReflectUtil.checkPackageAccess(className);
            Class<?> c = Class.forName(className, true, null);
            if (methodName != null) {
                Class[] types = getClassArray(args);
                Method m = c.getMethod(methodName, types);
                makeAccessible(m);
                return m.invoke(c, args);
            } else {
                Class[] types = getClassArray(args);
                Constructor constructor = c.getConstructor(types);
                makeAccessible(constructor);
                return constructor.newInstance(args);
            }
        } catch (Exception e) {
            // Ideally we would throw an exception, unfortunately
            // often times there are errors as an initial look and
            // feel is loaded before one can be switched. Perhaps a
            // flag should be added for debugging, so that if true
            // the exception would be thrown.
        }
        return null;
    }

    private void makeAccessible(final AccessibleObject object) {
        AccessController.doPrivileged(new PrivilegedAction<Void>() {
            public Void run() {
                object.setAccessible(true);
                return null;
            }
        });
    }

    private Class[] getClassArray(Object[] args) {
        Class[] types = null;
        if (args!=null) {
            types = new Class[args.length];
            for (int i = 0; i< args.length; i++) {
                /* PENDING(ges): At present only the primitive types
                   used are handled correctly; this should eventually
                   handle all primitive types */
                if (args[i] instanceof java.lang.Integer) {
                    types[i]=Integer.TYPE;
                } else if (args[i] instanceof java.lang.Boolean) {
                    types[i]=Boolean.TYPE;
                } else if (args[i] instanceof javax.swing.plaf.ColorUIResource) {
                    /* PENDING(ges) Currently the Reflection APIs do not
                       search superclasses of parameters supplied for
                       constructor/method lookup.  Since we only have
                       one case where this is needed, we substitute
                       directly instead of adding a massive amount
                       of mechanism for this.  Eventually this will
                       probably need to handle the general case as well.
                    */
                    types[i]=java.awt.Color.class;
                } else {
                    types[i]=args[i].getClass();
                }
            }
        }
        return types;
    }
}