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1 /* |
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2 * Copyright (c) 2003, 2018, 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 /** |
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27 * Provides utility classes to allow serializable mappings between SQL types |
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28 * and data types in the Java programming language. |
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29 * <p> Standard JDBC <code>RowSet</code> implementations may use these utility |
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30 * classes to |
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31 * assist in the serialization of disconnected <code>RowSet</code> objects. |
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32 * This is useful |
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33 * when transmitting a disconnected <code>RowSet</code> object over the wire to |
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34 * a different VM or across layers within an application.<br> |
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35 * </p> |
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36 * |
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37 * <h3>1.0 SerialArray</h3> |
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38 * A serializable mapping in the Java programming language of an SQL ARRAY |
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39 * value. <br> |
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40 * <br> |
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41 * The <code>SerialArray</code> class provides a constructor for creating a <code>SerialArray</code> |
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42 * instance from an Array object, methods for getting the base type and |
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43 * the SQL name for the base type, and methods for copying all or part of a |
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44 * <code>SerialArray</code> object. <br> |
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45 * |
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46 * <h3>2.0 SerialBlob</h3> |
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47 * A serializable mapping in the Java programming language of an SQL BLOB |
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48 * value. <br> |
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49 * <br> |
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50 * The <code>SerialBlob</code>class provides a constructor for creating an instance |
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51 * from a Blob object. Note that the Blob object should have brought the SQL |
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52 * BLOB value's data over to the client before a <code>SerialBlob</code>object |
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53 * is constructed from it. The data of an SQL BLOB value can be materialized |
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54 * on the client as an array of bytes (using the method <code>Blob.getBytes</code>) |
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55 * or as a stream of uninterpreted bytes (using the method <code>Blob.getBinaryStream</code>). |
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56 * <br> |
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57 * <br> |
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58 * <code>SerialBlob</code> methods make it possible to make a copy of a <code>SerialBlob</code> |
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59 * object as an array of bytes or as a stream. They also make it possible |
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60 * to locate a given pattern of bytes or a <code>Blob</code> object within a <code>SerialBlob</code> |
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61 * object. <br> |
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62 * |
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63 * <h3>3.0 SerialClob</h3> |
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64 * A serializable mapping in the Java programming language of an SQL CLOB |
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65 * value. <br> |
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66 * <br> |
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67 * The <code>SerialClob</code> class provides a constructor for creating an instance |
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68 * from a <code>Clob</code> object. Note that the <code>Clob</code> object should have |
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69 * brought the SQL CLOB value's data over to the client before a <code>SerialClob</code> |
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70 * object is constructed from it. The data of an SQL CLOB value can be |
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71 * materialized on the client as a stream of Unicode characters. <br> |
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72 * <br> |
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73 * <code>SerialClob</code> methods make it possible to get a substring from a |
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74 * <code>SerialClob</code> object or to locate the start of a pattern of characters. |
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75 * <br> |
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76 * |
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77 * <h3>5.0 SerialDatalink</h3> |
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78 * A serializable mapping in the Java programming language of an SQL DATALINK |
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79 * value. A DATALINK value references a file outside of the underlying data source |
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80 * that the originating data source manages. <br> |
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81 * <br> |
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82 * <code>RowSet</code> implementations can use the method <code>RowSet.getURL()</code> to retrieve |
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83 * a <code>java.net.URL</code> object, which can be used to manipulate the external data. |
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84 * <br> |
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85 * <br> |
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86 * <code> java.net.URL url = rowset.getURL(1);</code><br> |
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87 * |
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88 * <h3>6.0 SerialJavaObject</h3> |
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89 * A serializable mapping in the Java programming language of an SQL JAVA_OBJECT |
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90 * value. Assuming the Java object instance implements the Serializable interface, |
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91 * this simply wraps the serialization process. <br> |
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92 * <br> |
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93 * If however, the serialization is not possible in the case where the Java |
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94 * object is not immediately serializable, this class will attempt to serialize |
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95 * all non static members to permit the object instance state to be serialized. |
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96 * Static or transient fields cannot be serialized and attempting to do so |
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97 * will result in a <code>SerialException</code> being thrown. <br> |
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98 * |
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99 * <h3>7.0 SerialRef</h3> |
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100 * A serializable mapping between the SQL REF type and the Java programming |
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101 * language. <br> |
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102 * <br> |
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103 * The <code>SerialRef</code> class provides a constructor for creating a <code>SerialRef</code> |
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104 * instance from a <code>Ref</code> type and provides methods for getting |
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105 * and setting the <code>Ref</code> object type. <br> |
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106 * |
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107 * <h3>8.0 SerialStruct</h3> |
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108 * A serializable mapping in the Java programming language of an SQL structured |
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109 * type. Each attribute that is not already serializable is mapped to a serializable |
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110 * form, and if an attribute is itself a structured type, each of its attributes |
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111 * that is not already serializable is mapped to a serializable form. <br> |
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112 * <br> |
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113 * In addition, if a <code>Map</code> object is passed to one of the constructors or |
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114 * to the method <code>getAttributes</code>, the structured type is custom mapped |
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115 * according to the mapping specified in the <code>Map</code> object. |
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116 * <br> |
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117 * The <code>SerialStruct</code> class provides a constructor for creating an |
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118 * instance from a <code>Struct</code> object, a method for retrieving the SQL |
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119 * type name of the SQL structured type in the database, and methods for retrieving |
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120 * its attribute values. <br> |
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121 * |
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122 * <h3>9.0 SQLInputImpl</h3> |
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123 * An input stream used for custom mapping user-defined types (UDTs). An |
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124 * <code>SQLInputImpl</code> object is an input stream that contains a stream of |
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125 * values that are |
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126 * the attributes of a UDT. This class is used by the driver behind the scenes |
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127 * when the method <code>getObject</code> is called on an SQL structured or distinct |
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128 * type that has a custom mapping; a programmer never invokes <code>SQLInputImpl</code> |
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129 * methods directly. <br> |
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130 * <br> |
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131 * The <code>SQLInputImpl</code> class provides a set of reader methods |
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132 * analogous to the <code>ResultSet</code> getter methods. These methods make it |
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133 * possible to read the values in an <code>SQLInputImpl</code> object. The method |
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134 * <code>wasNull</code> is used to determine whether the last value read was SQL NULL. |
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135 * <br> |
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136 * <br> |
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137 * When a constructor or getter method that takes a <code>Map</code> object is called, |
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138 * the JDBC driver calls the method |
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139 * <code>SQLData.getSQLType</code> to determine the SQL type of the UDT being custom |
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140 * mapped. The driver creates an instance of <code>SQLInputImpl</code>, populating it with |
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141 * the attributes of the UDT. The driver then passes the input stream to the |
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142 * method <code>SQLData.readSQL</code>, which in turn calls the <code>SQLInputImpl</code> |
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143 * methods to read the attributes from the input stream. <br> |
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144 * |
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145 * <h3>10.0 SQLOutputImpl</h3> |
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146 * The output stream for writing the attributes of a custom mapped user-defined |
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147 * type (UDT) back to the database. The driver uses this interface internally, |
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148 * and its methods are never directly invoked by an application programmer. |
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149 * <br> |
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150 * <br> |
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151 * When an application calls the method <code>PreparedStatement.setObject</code>, the |
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152 * driver checks to see whether the value to be written is a UDT with a custom |
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153 * mapping. If it is, there will be an entry in a type map containing the Class |
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154 * object for the class that implements <code>SQLData</code> for this UDT. If the |
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155 * value to be written is an instance of <code>SQLData</code>, the driver will |
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156 * create an instance of <code>SQLOutputImpl</code> and pass it to the method |
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157 * <code>SQLData.writeSQL</code>. |
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158 * The method <code>writeSQL</code> in turn calls the appropriate <code>SQLOutputImpl</code> |
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159 * writer methods to write data from the <code>SQLData</code> object to the |
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160 * <code>SQLOutputImpl</code> |
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161 * output stream as the representation of an SQL user-defined type. |
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162 * |
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163 * <h3>Custom Mapping</h3> |
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164 * The JDBC API provides mechanisms for mapping an SQL structured type or DISTINCT |
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165 * type to the Java programming language. Typically, a structured type is mapped |
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166 * to a class, and its attributes are mapped to fields in the class. |
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167 * (A DISTINCT type can thought of as having one attribute.) However, there are |
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168 * many other possibilities, and there may be any number of different mappings. |
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169 * <P> |
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170 * A programmer defines the mapping by implementing the interface <code>SQLData</code>. |
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171 * For example, if an SQL structured type named AUTHORS has the attributes NAME, |
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172 * TITLE, and PUBLISHER, it could be mapped to a Java class named Authors. The |
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173 * Authors class could have the fields name, title, and publisher, to which the |
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174 * attributes of AUTHORS are mapped. In such a case, the implementation of |
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175 * <code>SQLData</code> could look like the following: |
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176 * <PRE> |
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177 * public class Authors implements SQLData { |
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178 * public String name; |
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179 * public String title; |
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180 * public String publisher; |
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181 * |
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182 * private String sql_type; |
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183 * public String getSQLTypeName() { |
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184 * return sql_type; |
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185 * } |
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186 * |
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187 * public void readSQL(SQLInput stream, String type) |
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188 * throws SQLException { |
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189 * sql_type = type; |
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190 * name = stream.readString(); |
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191 * title = stream.readString(); |
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192 * publisher = stream.readString(); |
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193 * } |
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194 * |
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195 * public void writeSQL(SQLOutput stream) throws SQLException { |
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196 * stream.writeString(name); |
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197 * stream.writeString(title); |
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198 * stream.writeString(publisher); |
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199 * } |
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200 * } |
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201 * </PRE> |
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202 * |
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203 * A <code>java.util.Map</code> object is used to associate the SQL structured |
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204 * type with its mapping to the class <code>Authors</code>. The following code fragment shows |
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205 * how a <code>Map</code> object might be created and given an entry associating |
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206 * <code>AUTHORS</code> and <code>Authors</code>. |
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207 * <PRE> |
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208 * java.util.Map map = new java.util.HashMap(); |
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209 * map.put("SCHEMA_NAME.AUTHORS", Class.forName("Authors"); |
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210 * </PRE> |
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211 * |
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212 * The <code>Map</code> object <i>map</i> now contains an entry with the |
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213 * fully qualified name of the SQL structured type and the <code>Class</code> |
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214 * object for the class <code>Authors</code>. It can be passed to a method |
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215 * to tell the driver how to map <code>AUTHORS</code> to <code>Authors</code>. |
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216 * <P> |
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217 * For a disconnected <code>RowSet</code> object, custom mapping can be done |
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218 * only when a <code>Map</code> object is passed to the method or constructor |
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219 * that will be doing the custom mapping. The situation is different for |
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220 * connected <code>RowSet</code> objects because they maintain a connection |
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221 * with the data source. A method that does custom mapping and is called by |
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222 * a disconnected <code>RowSet</code> object may use the <code>Map</code> |
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223 * object that is associated with the <code>Connection</code> object being |
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224 * used. So, in other words, if no map is specified, the connection's type |
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225 * map can be used by default. |
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226 */ |
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227 package javax.sql.rowset.serial; |