| /* java.beans.Expression |
| Copyright (C) 2004 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package java.beans; |
| |
| /** |
| * class Expression |
| * |
| * An Expression captures the execution of an object method that |
| * returns a value. It stores an object, the method to call, and the |
| * arguments to pass to the method. |
| * |
| * @since 1.4 |
| */ |
| public class Expression extends Statement |
| { |
| // This is a placeholder to indicate that value hasn't been set |
| // yet; |
| private static final Object unset = new Object(); |
| |
| // The value to return. This is equal to unset until getValue is called. |
| private Object value; |
| |
| |
| /** |
| * Constructor |
| * |
| * Constructs an Expression representing the invocation of |
| * object.methodName(arg[0], arg[1], ...); However, it will never |
| * be executed. Instead, value will always be returned. |
| * |
| * @param value The value to return. |
| * @param target The object to invoke the method on. |
| * @param methodName The object method to invoke. |
| * @param arguments An array of arguments to pass to the method. |
| */ |
| public Expression(Object value, Object target, String methodName, |
| Object[] arguments) |
| { |
| super(target, methodName, arguments); |
| this.value = value; |
| } |
| |
| /** |
| * Constructor |
| * |
| * Constructs an Expression representing the invocation of |
| * object.methodName(arg[0], arg[1], ...); |
| * |
| * @param target The object to invoke the method on. |
| * @param methodName The object method to invoke. |
| * @param arguments An array of arguments to pass to the method. |
| */ |
| public Expression(Object target, String methodName, Object[] arguments) |
| { |
| super(target, methodName, arguments); |
| this.value = unset; |
| } |
| |
| /** |
| * Return the result of executing the method. |
| * |
| * If the cached value has not yet been set, the method is |
| * executed in the same way as Statement.execute(), except that |
| * the value is cached, and then returned. If the value has been |
| * set, it is returned without executing the method again. |
| * |
| * @return the result of executing the method. |
| * @exception Exception if an error occurs |
| */ |
| public Object getValue() throws Exception |
| { |
| if (value == unset) |
| value = doExecute(); |
| return value; |
| } |
| |
| /** |
| * Set the cached value to be returned by getValue() |
| * |
| * @param value the value to cache and return. |
| */ |
| public void setValue(Object value) |
| { |
| this.value = value; |
| } |
| |
| /** |
| * Return a string representation of this expression. |
| */ |
| public String toString() |
| { |
| String result = super.toString(); |
| if (value != unset) |
| return value.getClass().getName() + " " + result; |
| return result; |
| } |
| } |