GNU Classpath (0.19) | ||
Frames | No Frames |
1: /* java.beans.Expression 2: Copyright (C) 2004, 2005 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package java.beans; 40: 41: /** 42: * class Expression 43: * 44: * An Expression captures the execution of an object method that 45: * returns a value. It stores an object, the method to call, and the 46: * arguments to pass to the method. 47: * 48: * @since 1.4 49: */ 50: public class Expression extends Statement 51: { 52: // This is a placeholder to indicate that value hasn't been set 53: // yet; 54: private static final Object UNSET = new Object(); 55: 56: // The value to return. This is equal to unset until getValue is called. 57: private Object value; 58: 59: 60: /** 61: * Constructor 62: * 63: * Constructs an Expression representing the invocation of 64: * object.methodName(arg[0], arg[1], ...); However, it will never 65: * be executed. Instead, value will always be returned. 66: * 67: * @param value The value to return. 68: * @param target The object to invoke the method on. 69: * @param methodName The object method to invoke. 70: * @param arguments An array of arguments to pass to the method. 71: */ 72: public Expression(Object value, Object target, String methodName, 73: Object[] arguments) 74: { 75: super(target, methodName, arguments); 76: this.value = value; 77: } 78: 79: /** 80: * Constructor 81: * 82: * Constructs an Expression representing the invocation of 83: * object.methodName(arg[0], arg[1], ...); 84: * 85: * @param target The object to invoke the method on. 86: * @param methodName The object method to invoke. 87: * @param arguments An array of arguments to pass to the method. 88: */ 89: public Expression(Object target, String methodName, Object[] arguments) 90: { 91: super(target, methodName, arguments); 92: this.value = UNSET; 93: } 94: 95: /** 96: * Return the result of executing the method. 97: * 98: * If the cached value has not yet been set, the method is 99: * executed in the same way as Statement.execute(), except that 100: * the value is cached, and then returned. If the value has been 101: * set, it is returned without executing the method again. 102: * 103: * @return the result of executing the method. 104: * @exception Exception if an error occurs 105: */ 106: public Object getValue() throws Exception 107: { 108: if (value == UNSET) 109: value = doExecute(); 110: return value; 111: } 112: 113: /** 114: * Set the cached value to be returned by getValue() 115: * 116: * @param value the value to cache and return. 117: */ 118: public void setValue(Object value) 119: { 120: this.value = value; 121: } 122: 123: /** 124: * Return a string representation of this expression. 125: */ 126: public String toString() 127: { 128: String result = super.toString(); 129: if (value != UNSET) 130: return value.getClass().getName() + " " + result; 131: return result; 132: } 133: }
GNU Classpath (0.19) |