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1 /* |
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2 * Copyright (c) 2004, 2013, 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.xml.bind.annotation.adapters; |
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27 |
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28 /** |
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29 * Adapts a Java type for custom marshaling. |
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30 * |
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31 * <p> <b> Usage: </b> </p> |
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32 * |
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33 * <p> |
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34 * Some Java types do not map naturally to a XML representation, for |
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35 * example <tt>HashMap</tt> or other non JavaBean classes. Conversely, |
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36 * a XML repsentation may map to a Java type but an application may |
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37 * choose to accesss the XML representation using another Java |
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38 * type. For example, the schema to Java binding rules bind |
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39 * xs:DateTime by default to XmlGregorianCalendar. But an application |
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40 * may desire to bind xs:DateTime to a custom type, |
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41 * MyXmlGregorianCalendar, for example. In both cases, there is a |
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42 * mismatch between <i> bound type </i>, used by an application to |
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43 * access XML content and the <i> value type</i>, that is mapped to an |
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44 * XML representation. |
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45 * |
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46 * <p> |
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47 * This abstract class defines methods for adapting a bound type to a value |
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48 * type or vice versa. The methods are invoked by the JAXB binding |
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49 * framework during marshaling and unmarshalling: |
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50 * |
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51 * <ul> |
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52 * <li> <b> XmlAdapter.marshal(...): </b> During marshalling, JAXB |
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53 * binding framework invokes XmlAdapter.marshal(..) to adapt a |
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54 * bound type to value type, which is then marshaled to XML |
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55 * representation. </li> |
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56 * |
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57 * <li> <b> XmlAdapter.unmarshal(...): </b> During unmarshalling, |
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58 * JAXB binding framework first unmarshals XML representation |
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59 * to a value type and then invokes XmlAdapter.unmarshal(..) to |
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60 * adapt the value type to a bound type. </li> |
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61 * </ul> |
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62 * |
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63 * Writing an adapter therefore involves the following steps: |
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64 * |
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65 * <ul> |
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66 * <li> Write an adapter that implements this abstract class. </li> |
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67 * <li> Install the adapter using the annotation {@link |
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68 * XmlJavaTypeAdapter} </li> |
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69 * </ul> |
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70 * |
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71 * <p><b>Example:</b> Customized mapping of <tt>HashMap</tt></p> |
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72 * <p> The following example illustrates the use of |
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73 * <tt>@XmlAdapter</tt> and <tt>@XmlJavaTypeAdapter</tt> to |
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74 * customize the mapping of a <tt>HashMap</tt>. |
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75 * |
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76 * <p> <b> Step 1: </b> Determine the desired XML representation for HashMap. |
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77 * |
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78 * <pre> |
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79 * <hashmap> |
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80 * <entry key="id123">this is a value</entry> |
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81 * <entry key="id312">this is another value</entry> |
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82 * ... |
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83 * </hashmap> |
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84 * </pre> |
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85 * |
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86 * <p> <b> Step 2: </b> Determine the schema definition that the |
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87 * desired XML representation shown above should follow. |
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88 * |
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89 * <pre> |
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90 * |
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91 * <xs:complexType name="myHashMapType"> |
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92 * <xs:sequence> |
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93 * <xs:element name="entry" type="myHashMapEntryType" |
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94 * minOccurs = "0" maxOccurs="unbounded"/> |
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95 * </xs:sequence> |
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96 * </xs:complexType> |
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97 * |
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98 * <xs:complexType name="myHashMapEntryType"> |
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99 * <xs:simpleContent> |
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100 * <xs:extension base="xs:string"> |
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101 * <xs:attribute name="key" type="xs:int"/> |
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102 * </xs:extension> |
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103 * </xs:simpleContent> |
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104 * </xs:complexType> |
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105 * |
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106 * </pre> |
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107 * |
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108 * <p> <b> Step 3: </b> Write value types that can generate the above |
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109 * schema definition. |
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110 * |
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111 * <pre> |
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112 * public class MyHashMapType { |
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113 * List<MyHashMapEntryType> entry; |
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114 * } |
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115 * |
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116 * public class MyHashMapEntryType { |
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117 * @XmlAttribute |
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118 * public Integer key; |
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119 * |
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120 * @XmlValue |
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121 * public String value; |
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122 * } |
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123 * </pre> |
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124 * |
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125 * <p> <b> Step 4: </b> Write the adapter that adapts the value type, |
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126 * MyHashMapType to a bound type, HashMap, used by the application. |
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127 * |
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128 * <pre> |
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129 * public final class MyHashMapAdapter extends |
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130 * XmlAdapter<MyHashMapType,HashMap> { ... } |
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131 * |
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132 * </pre> |
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133 * |
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134 * <p> <b> Step 5: </b> Use the adapter. |
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135 * |
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136 * <pre> |
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137 * public class Foo { |
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138 * @XmlJavaTypeAdapter(MyHashMapAdapter.class) |
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139 * HashMap hashmap; |
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140 * ... |
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141 * } |
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142 * </pre> |
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143 * |
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144 * The above code fragment will map to the following schema: |
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145 * |
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146 * <pre> |
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147 * <xs:complexType name="Foo"> |
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148 * <xs:sequence> |
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149 * <xs:element name="hashmap" type="myHashMapType" |
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150 * </xs:sequence> |
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151 * </xs:complexType> |
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152 * </pre> |
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153 * |
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154 * @param <BoundType> |
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155 * The type that JAXB doesn't know how to handle. An adapter is written |
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156 * to allow this type to be used as an in-memory representation through |
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157 * the <tt>ValueType</tt>. |
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158 * @param <ValueType> |
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159 * The type that JAXB knows how to handle out of the box. |
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160 * |
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161 * @author <ul><li>Sekhar Vajjhala, Sun Microsystems Inc.</li> <li> Kohsuke Kawaguchi, Sun Microsystems Inc.</li></ul> |
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162 * @see XmlJavaTypeAdapter |
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163 * @since JAXB 2.0 |
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164 */ |
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165 public abstract class XmlAdapter<ValueType,BoundType> { |
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166 |
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167 /** |
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168 * Do-nothing constructor for the derived classes. |
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169 */ |
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170 protected XmlAdapter() {} |
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171 |
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172 /** |
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173 * Convert a value type to a bound type. |
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174 * |
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175 * @param v |
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176 * The value to be converted. Can be null. |
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177 * @throws Exception |
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178 * if there's an error during the conversion. The caller is responsible for |
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179 * reporting the error to the user through {@link javax.xml.bind.ValidationEventHandler}. |
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180 */ |
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181 public abstract BoundType unmarshal(ValueType v) throws Exception; |
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182 |
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183 /** |
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184 * Convert a bound type to a value type. |
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185 * |
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186 * @param v |
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187 * The value to be convereted. Can be null. |
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188 * @throws Exception |
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189 * if there's an error during the conversion. The caller is responsible for |
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190 * reporting the error to the user through {@link javax.xml.bind.ValidationEventHandler}. |
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191 */ |
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192 public abstract ValueType marshal(BoundType v) throws Exception; |
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193 } |