/*
 * Copyright (c) 1997, 2017, 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 javax.activation;

import java.io.*;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;

The CommandInfo class is used by CommandMap implementations to describe the results of command requests. It provides the requestor with both the verb requested, as well as an instance of the bean. There is also a method that will return the name of the class that implements the command but it is not guaranteed to return a valid value. The reason for this is to allow CommandMap implmentations that subclass CommandInfo to provide special behavior. For example a CommandMap could dynamically generate JavaBeans. In this case, it might not be possible to create an object with all the correct state information solely from the class name.
Since:1.6
/** * The CommandInfo class is used by CommandMap implementations to * describe the results of command requests. It provides the requestor * with both the verb requested, as well as an instance of the * bean. There is also a method that will return the name of the * class that implements the command but <i>it is not guaranteed to * return a valid value</i>. The reason for this is to allow CommandMap * implmentations that subclass CommandInfo to provide special * behavior. For example a CommandMap could dynamically generate * JavaBeans. In this case, it might not be possible to create an * object with all the correct state information solely from the class * name. * * @since 1.6 */
public class CommandInfo { private String verb; private String className;
The Constructor for CommandInfo.
Params:
  • verb – The command verb this CommandInfo decribes.
  • className – The command's fully qualified class name.
/** * The Constructor for CommandInfo. * @param verb The command verb this CommandInfo decribes. * @param className The command's fully qualified class name. */
public CommandInfo(String verb, String className) { this.verb = verb; this.className = className; }
Return the command verb.
Returns:the command verb.
/** * Return the command verb. * * @return the command verb. */
public String getCommandName() { return verb; }
Return the command's class name. This method MAY return null in cases where a CommandMap subclassed CommandInfo for its own purposes. In other words, it might not be possible to create the correct state in the command by merely knowing its class name. DO NOT DEPEND ON THIS METHOD RETURNING A VALID VALUE!
Returns:The class name of the command, or null
/** * Return the command's class name. <i>This method MAY return null in * cases where a CommandMap subclassed CommandInfo for its * own purposes.</i> In other words, it might not be possible to * create the correct state in the command by merely knowing * its class name. <b>DO NOT DEPEND ON THIS METHOD RETURNING * A VALID VALUE!</b> * * @return The class name of the command, or <i>null</i> */
public String getCommandClass() { return className; }
Return the instantiated JavaBean component.

If java.beans.Beans is visible then it's java.beans.Beans#instantiate method is invoked to instantiate the component as a JavaBeans component. When java.beans.Beans is not visible (when java.desktop module is not readable or when the runtime image does not contain the java.desktop module) then the command's class is loaded and instantiated with its public no-args constructor.

The component class needs to be public.

If the bean implements the javax.activation.CommandObject interface, call its setCommandContext method.

If the DataHandler parameter is null, then the bean is instantiated with no data. NOTE: this may be useful if for some reason the DataHandler that is passed in throws IOExceptions when this method attempts to access its InputStream. It will allow the caller to retrieve a reference to the bean if it can be instantiated.

If the bean does NOT implement the CommandObject interface, this method will check if it implements the java.io.Externalizable interface. If it does, the bean's readExternal method will be called if an InputStream can be acquired from the DataHandler.

Params:
  • dh – The DataHandler that describes the data to be passed to the command.
  • loader – The ClassLoader to be used to instantiate the bean.
Throws:
See Also:
Returns:The bean
/** * Return the instantiated JavaBean component. * <p> * If {@code java.beans.Beans} is visible then it's * {@code java.beans.Beans#instantiate} method is invoked to instantiate * the component as a JavaBeans component. * When {@code java.beans.Beans} is not visible (when {@code java.desktop} * module is not readable or when the runtime image does not contain the * {@code java.desktop} module) then the command's class is loaded and * instantiated with its public no-args constructor. * <p> * The component class needs to be public. * <p> * If the bean implements the {@code javax.activation.CommandObject} * interface, call its {@code setCommandContext} method. * <p> * If the DataHandler parameter is null, then the bean is * instantiated with no data. NOTE: this may be useful * if for some reason the DataHandler that is passed in * throws IOExceptions when this method attempts to * access its InputStream. It will allow the caller to * retrieve a reference to the bean if it can be * instantiated. * <p> * If the bean does NOT implement the CommandObject interface, * this method will check if it implements the * java.io.Externalizable interface. If it does, the bean's * readExternal method will be called if an InputStream * can be acquired from the DataHandler.<p> * * @param dh The DataHandler that describes the data to be * passed to the command. * @param loader The ClassLoader to be used to instantiate the bean. * @return The bean * @exception IOException for failures reading data * @exception ClassNotFoundException if command object class can't * be found * @see java.beans.Beans#instantiate * @see javax.activation.CommandObject */
public Object getCommandObject(DataHandler dh, ClassLoader loader) throws IOException, ClassNotFoundException { Object new_bean = null; // try to instantiate the bean new_bean = Beans.instantiate(loader, className); // if we got one and it is a CommandObject if (new_bean != null) { if (new_bean instanceof CommandObject) { ((CommandObject)new_bean).setCommandContext(verb, dh); } else if (new_bean instanceof Externalizable) { if (dh != null) { InputStream is = dh.getInputStream(); if (is != null) { ((Externalizable)new_bean).readExternal( new ObjectInputStream(is)); } } } } return new_bean; }
Helper class to invoke Beans.instantiate reflectively or the equivalent with core reflection when module java.desktop is not readable.
/** * Helper class to invoke Beans.instantiate reflectively or the equivalent * with core reflection when module java.desktop is not readable. */
private static final class Beans { static final Method instantiateMethod; static { Method m; try { Class<?> c = Class.forName("java.beans.Beans"); m = c.getDeclaredMethod("instantiate", ClassLoader.class, String.class); } catch (ClassNotFoundException e) { m = null; } catch (NoSuchMethodException e) { m = null; } instantiateMethod = m; }
Equivalent to invoking java.beans.Beans.instantiate(loader, cn)
/** * Equivalent to invoking java.beans.Beans.instantiate(loader, cn) */
static Object instantiate(ClassLoader loader, String cn) throws IOException, ClassNotFoundException { Exception exception; if (instantiateMethod != null) { // invoke Beans.instantiate try { return instantiateMethod.invoke(null, loader, cn); } catch (InvocationTargetException e) { exception = e; } catch (IllegalAccessException e) { exception = e; } } else { SecurityManager security = System.getSecurityManager(); if (security != null) { // if it's ok with the SecurityManager, it's ok with me. String cname = cn.replace('/', '.'); if (cname.startsWith("[")) { int b = cname.lastIndexOf('[') + 2; if (b > 1 && b < cname.length()) { cname = cname.substring(b); } } int i = cname.lastIndexOf('.'); if (i != -1) { security.checkPackageAccess(cname.substring(0, i)); } } // Beans.instantiate specified to use SCL when loader is null if (loader == null) { loader = (ClassLoader) AccessController.doPrivileged(new PrivilegedAction() { public Object run() { ClassLoader cl = null; try { cl = ClassLoader.getSystemClassLoader(); } catch (SecurityException ex) { } return cl; } }); } Class<?> beanClass = Class.forName(cn, false, loader); try { return beanClass.getDeclaredConstructor().newInstance(); } catch (Exception ex) { throw new ClassNotFoundException(beanClass + ": " + ex, ex); } } return null; } } }