369 lines
14 KiB
Java
369 lines
14 KiB
Java
/* java.beans.Beans
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Copyright (C) 1998, 1999, 2004, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.beans;
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import gnu.java.beans.DummyAppletStub;
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import gnu.java.io.ClassLoaderObjectInputStream;
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import java.applet.Applet;
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import java.beans.beancontext.BeanContext;
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import java.io.IOException;
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import java.io.ObjectInputStream;
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import java.net.URL;
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/**
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* <code>Beans</code> provides some helper methods that allow the basic
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* operations of Bean-ness.
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*
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* @author John Keiser
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* @author Robert Schuster
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*
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* @since 1.1
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* @status updated to 1.4
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*
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*/
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public class Beans
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{
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static boolean designTime = false;
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static boolean guiAvailable = true;
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/**
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* Once again, we have a java.beans class with only
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* static methods that can be instantiated. When
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* will the madness end? :)
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*/
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public Beans()
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{
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// Does intentionally nothing here.
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}
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/** Creates a bean.
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* <p>This is a convenience method that calls <code>instantiate(cl, beanName, null, null)</code>.</p>
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*
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* @see instantiate(ClassLoader, String, BeanContext, AppletInitializer)
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* @param cl ClassLoader to be used or <code>null</code> for the system classloader.
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* @param beanName Name of a serialized bean or class name.
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* @return A newly created bean.
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* @throws IOException If access of an IO resource failed.
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* @throws ClassNotFoundException If the class name is not known or does not lead to a proper bean class.
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*/
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public static Object instantiate(ClassLoader cl, String beanName)
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throws IOException, ClassNotFoundException
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{
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return instantiate(cl, beanName, null, null);
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}
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/** Creates a bean.
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*
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* <p>This is a convenience method that calls <code>instantiate(cl, beanName, beanContext, null)</code>.</p>
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*
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* @see instantiate(ClassLoader, String, BeanContext, AppletInitializer)
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* @param cl ClassLoader to be used or <code>null</code> for the system classloader.
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* @param beanName Name of a serialized bean or class name.
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* @param beanContext Context to which the newly created Bean should be added.
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* @return A newly created bean.
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* @throws IOException If access of an IO resource failed.
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* @throws ClassNotFoundException If the class name is not known or does not lead to a proper bean class.
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*/
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public static Object instantiate(
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ClassLoader cl,
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String beanName,
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BeanContext beanContext)
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throws IOException, ClassNotFoundException
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{
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return instantiate(cl, beanName, beanContext, null);
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}
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/** Instantiates a bean according to Beans 1.0.
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*
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* <p>In Beans 1.0 the instantiation scheme is as follows:</p>
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* <p>The name should be dot-separated (e.g "place.for.beans.myBean") and indicate either a
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* serialized object or a class name. In the first case all dots in the name are replaced with
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* slashes ('/') and ".ser" is appended ("place.for.beans.myBean" becomes "place/for/beans/myBean.ser").
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* The bean is then loaded as an application or system resource depending on whether a
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* <code>ClassLoader</code> was provided.</p>
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*
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* <p>If no such resource exists or if it contains no bean the name is interpreted as a class name of
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* which an instance is then created.</p>
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*
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* <p>If a <code>BeanContext</code> instance is available the created bean is added to it.</p>
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*
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* <p>If the created Bean is an <code>Applet</code> or subclass and an <code>AppletInitializer</code>
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* instance is available the applet is initialized and afterwards activated using the initializer. Additionally
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* every instantiated <code>Applet</code> bean is initialized using the {@link Applet.init} method.
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* Furthermore every applet gets a default <code>AppletStub</code>. The <code>Applet</code>'s
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* document base is the location of the ".ser" file if it was deserialized or the location of its class
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* file if it was instantiated.</p>
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*
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* <p>A <code>ClassNotFoundException</code> is not only thrown when a class name was unknown
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* but even when the class has public no-argument constructor
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* (<code>IllegalAccessException</code> is wrapped) or an exception is thrown while
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* invoking such a constructor (causing exception is wrapped).</p>
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*
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* @param cl ClassLoader to be used or <code>null</code> for the system classloader.
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* @param beanName Name of a serialized bean or class name.
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* @param beanContext Context to which the newly created Bean should be added.
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* @param initializer The AppletInitializer which is used for initializing <code>Applet</code> beans.
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* @return A newly created bean.
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* @throws IOException If access of an IO resource failed.
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* @throws ClassNotFoundException If the class name is not known or does not lead to a proper bean class.
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*/
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public static Object instantiate(
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ClassLoader cl,
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String beanName,
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BeanContext beanContext,
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AppletInitializer initializer)
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throws IOException, ClassNotFoundException
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{
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Object bean = null;
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URL beanLocation = null;
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URL classLocation = null;
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// Converts bean name into a resource name (eg. "a.b.c" -> "a/b/c").
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String resourceName = beanName.replace('.', '/');
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/* Tries to get an input stream of the Bean, reading it as a system resource
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* if no ClassLoader is present or as an application resource if a classloader
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* is given.
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*/
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beanLocation =
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(cl == null)
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? ClassLoader.getSystemResource(resourceName + ".ser")
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: cl.getResource(resourceName + ".ser");
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// Reads the serialized Bean from the returned URL.
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if (beanLocation != null)
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{
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// Deserializes the bean instance.
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ObjectInputStream ois =
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(cl == null)
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? new ObjectInputStream(beanLocation.openStream())
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: new ClassLoaderObjectInputStream(
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beanLocation.openStream(),
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cl);
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bean = ois.readObject();
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/* Implementation note: The result of ObjectInputStream.readObject()
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* may have been null at this point (its a valid value to deserialize)
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* and we explicitly want to try instantiation in such a case
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* (this is important for compatibility).
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*/
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}
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// Instantiates the Bean using reflective instantiation if it has not been created yet.
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if (bean == null)
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{
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// Makes sure that the deserialization was NOT done.
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beanLocation = null;
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Class beanClass;
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if (cl == null)
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{
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beanClass = Class.forName(beanName);
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classLocation =
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ClassLoader.getSystemResource(resourceName + ".class");
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}
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else
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{
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beanClass = cl.loadClass(beanName);
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classLocation = cl.getResource(resourceName + ".class");
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}
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// Instantiates and optionally registers the new bean.
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try
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{
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bean = beanClass.newInstance();
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}
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catch(Exception e) {
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/* Wraps all kinds of Exceptions in a ClassNotFoundException (this behavior
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* matches with official >= 1.5, this was different for <=1.4)
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*/
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throw new ClassNotFoundException(null, e);
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}
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}
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/* Applet beans are treated in the following way:
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* - all AppletS get a default AppletStub
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* - all AppletS are initialized using the AppletInitializer instance (if it is available)
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* - as every other Bean Applets are added to a BeanContext if one is available
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* - each instantiated Applet is initialized using Applet.init() (this is not done for deserialized ones)
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* - finally AppletS get activated using the AppletInitializerS activate-Method
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*
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* The order of operations is important for compatibility.
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*/
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Applet applet = null;
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if (bean instanceof Applet)
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{
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// Makes a second instanceof call unneccessary (instanceof is expensive).
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applet = (Applet) bean;
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/* The AppletStub's code and document base is set as follows:
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* The code base is always the URL from where the class data originated
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* (without the package name).
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* If the Applet was deserialized the document base is the location of
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* the serialized instance (usually the ".ser" file) otherwise its the URL
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* from where the class data originated (usually the absolute directory
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* location of the ".class" file).
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*/
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applet.setStub(
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new DummyAppletStub(
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applet
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.getClass()
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.getProtectionDomain()
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.getCodeSource()
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.getLocation(),
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(beanLocation == null) ? classLocation : beanLocation));
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// Runs the Applet's initialization using an AppletInitializer.
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if (initializer != null)
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{
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initializer.initialize(applet, beanContext);
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}
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}
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// Adds the new bean to its BeanContext.
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if (beanContext != null)
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{
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beanContext.add(bean);
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}
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if (applet != null)
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{
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// Initializes an instantiated (not deserialized) Applet using its own method.
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if (beanLocation == null)
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{
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applet.init();
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}
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// Runs the Applet's activation using an AppletInitializer.
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if (initializer != null)
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{
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initializer.activate(applet);
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}
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}
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return bean;
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}
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/**
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* Returns the Bean as a different class type.
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* This should be used instead of casting to get a new
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* type view of a Bean, because in the future there may
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* be new types of Bean, even Beans spanning multiple
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* Objects.
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*
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* @param bean the Bean to cast.
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* @param newClass the Class to cast it to.
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*
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* @return the Bean as a new view, or if the operation
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* could not be performed, the Bean itself.
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*/
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public static Object getInstanceOf(Object bean, Class newClass)
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{
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return bean;
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}
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/**
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* Determines whether the Bean can be cast to a different
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* class type.
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* This should be used instead of instanceof to determine
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* a Bean's castability, because in the future there may
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* be new types of Bean, even Beans spanning multiple
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* Objects.
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*
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* @param bean the Bean to cast.
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* @param newClass the Class to cast it to.
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*
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* @return whether the Bean can be cast to the class type
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* in question.
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*/
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public static boolean isInstanceOf(Object bean, Class newBeanClass)
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{
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return newBeanClass.isInstance(bean);
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}
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/**
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* Returns whether the GUI is available to use.
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* <p>Defaults to true.</p>
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*
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* @return whether the GUI is available to use.
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*/
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public static boolean isGuiAvailable()
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{
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return guiAvailable;
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}
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/**
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* Returns whether it is design time. Design time means
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* we are in a RAD tool.
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* <p>Defaults to false.</p>
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*
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* @return whether it is design time.
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*/
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public static boolean isDesignTime()
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{
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return designTime;
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}
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/**
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* Sets whether the GUI is available to use.
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*
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* @param guiAvailable whether the GUI is available to use.
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*/
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public static void setGuiAvailable(boolean guiAvailable)
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throws SecurityException
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{
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Beans.guiAvailable = guiAvailable;
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}
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/**
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* Sets whether it is design time. Design time means we
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* are in a RAD tool.
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*
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* @param designTime whether it is design time.
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*/
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public static void setDesignTime(boolean designTime)
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throws SecurityException
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{
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Beans.designTime = designTime;
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}
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}
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