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1 /* |
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2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 package javax.activation; |
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27 |
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28 import java.io.*; |
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29 import java.beans.Beans; |
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30 |
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31 /** |
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32 * The CommandInfo class is used by CommandMap implementations to |
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33 * describe the results of command requests. It provides the requestor |
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34 * with both the verb requested, as well as an instance of the |
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35 * bean. There is also a method that will return the name of the |
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36 * class that implements the command but <i>it is not guaranteed to |
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37 * return a valid value</i>. The reason for this is to allow CommandMap |
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38 * implmentations that subclass CommandInfo to provide special |
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39 * behavior. For example a CommandMap could dynamically generate |
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40 * JavaBeans. In this case, it might not be possible to create an |
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41 * object with all the correct state information solely from the class |
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42 * name. |
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43 * |
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44 * @since 1.6 |
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45 */ |
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46 |
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47 public class CommandInfo { |
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48 private String verb; |
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49 private String className; |
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50 |
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51 /** |
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52 * The Constructor for CommandInfo. |
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53 * @param verb The command verb this CommandInfo decribes. |
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54 * @param className The command's fully qualified class name. |
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55 */ |
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56 public CommandInfo(String verb, String className) { |
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57 this.verb = verb; |
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58 this.className = className; |
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59 } |
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60 |
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61 /** |
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62 * Return the command verb. |
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63 * |
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64 * @return the command verb. |
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65 */ |
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66 public String getCommandName() { |
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67 return verb; |
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68 } |
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69 |
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70 /** |
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71 * Return the command's class name. <i>This method MAY return null in |
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72 * cases where a CommandMap subclassed CommandInfo for its |
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73 * own purposes.</i> In other words, it might not be possible to |
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74 * create the correct state in the command by merely knowing |
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75 * its class name. <b>DO NOT DEPEND ON THIS METHOD RETURNING |
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76 * A VALID VALUE!</b> |
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77 * |
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78 * @return The class name of the command, or <i>null</i> |
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79 */ |
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80 public String getCommandClass() { |
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81 return className; |
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82 } |
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83 |
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84 /** |
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85 * Return the instantiated JavaBean component. |
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86 * <p> |
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87 * Begin by instantiating the component with |
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88 * <code>Beans.instantiate()</code>. |
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89 * <p> |
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90 * If the bean implements the <code>javax.activation.CommandObject</code> |
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91 * interface, call its <code>setCommandContext</code> method. |
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92 * <p> |
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93 * If the DataHandler parameter is null, then the bean is |
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94 * instantiated with no data. NOTE: this may be useful |
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95 * if for some reason the DataHandler that is passed in |
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96 * throws IOExceptions when this method attempts to |
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97 * access its InputStream. It will allow the caller to |
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98 * retrieve a reference to the bean if it can be |
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99 * instantiated. |
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100 * <p> |
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101 * If the bean does NOT implement the CommandObject interface, |
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102 * this method will check if it implements the |
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103 * java.io.Externalizable interface. If it does, the bean's |
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104 * readExternal method will be called if an InputStream |
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105 * can be acquired from the DataHandler.<p> |
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106 * |
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107 * @param dh The DataHandler that describes the data to be |
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108 * passed to the command. |
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109 * @param loader The ClassLoader to be used to instantiate the bean. |
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110 * @return The bean |
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111 * @see java.beans.Beans#instantiate |
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112 * @see javax.activation.CommandObject |
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113 */ |
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114 public Object getCommandObject(DataHandler dh, ClassLoader loader) |
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115 throws IOException, ClassNotFoundException { |
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116 Object new_bean = null; |
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117 |
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118 // try to instantiate the bean |
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119 new_bean = java.beans.Beans.instantiate(loader, className); |
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120 |
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121 // if we got one and it is a CommandObject |
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122 if (new_bean != null) { |
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123 if (new_bean instanceof CommandObject) { |
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124 ((CommandObject)new_bean).setCommandContext(verb, dh); |
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125 } else if (new_bean instanceof Externalizable) { |
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126 if (dh != null) { |
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127 InputStream is = dh.getInputStream(); |
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128 if (is != null) { |
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129 ((Externalizable)new_bean).readExternal( |
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130 new ObjectInputStream(is)); |
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131 } |
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132 } |
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133 } |
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134 } |
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135 |
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136 return new_bean; |
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137 } |
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138 } |