| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.sql.GenericResultDescription |
| 4 | |
| 5 | Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable. |
| 6 | |
| 7 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | you may not use this file except in compliance with the License. |
| 9 | You may obtain a copy of the License at |
| 10 | |
| 11 | http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | |
| 13 | Unless required by applicable law or agreed to in writing, software |
| 14 | distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | See the License for the specific language governing permissions and |
| 17 | limitations under the License. |
| 18 | |
| 19 | */ |
| 20 | |
| 21 | package org.apache.derby.impl.sql; |
| 22 | |
| 23 | import org.apache.derby.iapi.sql.ResultColumnDescriptor; |
| 24 | import org.apache.derby.iapi.sql.ResultDescription; |
| 25 | |
| 26 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 27 | |
| 28 | import org.apache.derby.iapi.services.io.StoredFormatIds; |
| 29 | import org.apache.derby.iapi.services.io.FormatIdUtil; |
| 30 | import org.apache.derby.iapi.services.io.Formatable; |
| 31 | |
| 32 | import java.io.ObjectOutput; |
| 33 | import java.io.ObjectInput; |
| 34 | import java.io.IOException; |
| 35 | /** |
| 36 | * GenericResultDescription: basic implementation of result |
| 37 | * description, used in conjunction with the other |
| 38 | * implementations in this package. This implementation |
| 39 | * of ResultDescription may be used by anyone. |
| 40 | * |
| 41 | * @author ames |
| 42 | */ |
| 43 | public final class GenericResultDescription |
| 44 | implements ResultDescription, Formatable |
| 45 | { |
| 46 | |
| 47 | /******************************************************** |
| 48 | ** |
| 49 | ** This class implements Formatable. That means that it |
| 50 | ** can write itself to and from a formatted stream. If |
| 51 | ** you add more fields to this class, make sure that you |
| 52 | ** also write/read them with the writeExternal()/readExternal() |
| 53 | ** methods. |
| 54 | ** |
| 55 | ** If, inbetween releases, you add more fields to this class, |
| 56 | ** then you should bump the version number emitted by the getTypeFormatId() |
| 57 | ** method. |
| 58 | ** |
| 59 | ********************************************************/ |
| 60 | |
| 61 | private ResultColumnDescriptor[] columns; |
| 62 | private String statementType; |
| 63 | |
| 64 | /** |
| 65 | * Niladic constructor for Formatable |
| 66 | */ |
| 67 | public GenericResultDescription() |
| 68 | { |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * Build a GenericResultDescription from columns and type |
| 73 | * |
| 74 | * @param columns an array of col descriptors |
| 75 | * @param statementType the type |
| 76 | */ |
| 77 | public GenericResultDescription(ResultColumnDescriptor[] columns, |
| 78 | String statementType) |
| 79 | { |
| 80 | this.columns = columns; |
| 81 | this.statementType = statementType; |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * Build a GenericResultDescription |
| 86 | * |
| 87 | * @param rd the result description |
| 88 | * @param theCols the columns to take from the input rd |
| 89 | */ |
| 90 | public GenericResultDescription |
| 91 | ( |
| 92 | ResultDescription rd, |
| 93 | int[] theCols |
| 94 | ) |
| 95 | { |
| 96 | if (SanityManager.DEBUG) |
| 97 | { |
| 98 | SanityManager.ASSERT(theCols != null, "theCols argument to GenericResultDescription is null"); |
| 99 | } |
| 100 | |
| 101 | this.columns = new ResultColumnDescriptor[theCols.length]; |
| 102 | for (int i = 0; i < theCols.length; i++) |
| 103 | { |
| 104 | columns[i] = rd.getColumnDescriptor(theCols[i]); |
| 105 | } |
| 106 | this.statementType = rd.getStatementType(); |
| 107 | } |
| 108 | |
| 109 | // |
| 110 | // ResultDescription interface |
| 111 | // |
| 112 | /** |
| 113 | * @see ResultDescription#getStatementType |
| 114 | */ |
| 115 | public String getStatementType() { |
| 116 | return statementType; |
| 117 | } |
| 118 | |
| 119 | /** |
| 120 | * @see ResultDescription#getColumnCount |
| 121 | */ |
| 122 | public int getColumnCount() |
| 123 | { |
| 124 | return (columns == null) ? 0 : columns.length; |
| 125 | } |
| 126 | |
| 127 | public ResultColumnDescriptor[] getColumnInfo() { |
| 128 | return columns; |
| 129 | } |
| 130 | |
| 131 | /** |
| 132 | * position is 1-based. |
| 133 | * @see ResultDescription#getColumnDescriptor |
| 134 | */ |
| 135 | public ResultColumnDescriptor getColumnDescriptor(int position) { |
| 136 | return columns[position-1]; |
| 137 | } |
| 138 | |
| 139 | /** |
| 140 | * Get a new result description that has been truncated |
| 141 | * from input column number. If the input column is |
| 142 | * 5, then columns 5 to getColumnCount() are removed. |
| 143 | * The new ResultDescription points to the same |
| 144 | * ColumnDescriptors (this method performs a shallow |
| 145 | * copy. |
| 146 | * |
| 147 | * @param truncateFrom the starting column to remove |
| 148 | * |
| 149 | * @return a new ResultDescription |
| 150 | */ |
| 151 | public ResultDescription truncateColumns(int truncateFrom) |
| 152 | { |
| 153 | if (SanityManager.DEBUG) |
| 154 | { |
| 155 | if (!(truncateFrom > 0 && columns != null)) |
| 156 | { |
| 157 | SanityManager.THROWASSERT("bad truncate value: "+truncateFrom+" is too low"); |
| 158 | } |
| 159 | if (truncateFrom > columns.length) |
| 160 | { |
| 161 | SanityManager.THROWASSERT("bad truncate value: "+truncateFrom+" is too high"); |
| 162 | } |
| 163 | } |
| 164 | ResultColumnDescriptor[] newColumns = new ResultColumnDescriptor[truncateFrom-1]; |
| 165 | System.arraycopy(columns, 0, newColumns, 0, newColumns.length); |
| 166 | return new GenericResultDescription(newColumns, statementType); |
| 167 | } |
| 168 | |
| 169 | |
| 170 | ////////////////////////////////////////////// |
| 171 | // |
| 172 | // FORMATABLE |
| 173 | // |
| 174 | ////////////////////////////////////////////// |
| 175 | /** |
| 176 | * Write this object out |
| 177 | * |
| 178 | * @param out write bytes here |
| 179 | * |
| 180 | * @exception IOException thrown on error |
| 181 | */ |
| 182 | public void writeExternal(ObjectOutput out) throws IOException |
| 183 | { |
| 184 | int len = (columns == null) ? 0 : columns.length; |
| 185 | |
| 186 | out.writeObject(statementType); |
| 187 | out.writeInt(len); |
| 188 | while(len-- > 0) |
| 189 | { |
| 190 | /* |
| 191 | ** If we don't have a GenericColumnsDescriptor, |
| 192 | ** create one now and use that to write out. |
| 193 | ** Do this to avoid writing out query tree |
| 194 | ** implementations of ResultColumnDescriptor |
| 195 | */ |
| 196 | if (!(columns[len] instanceof |
| 197 | GenericColumnDescriptor)) |
| 198 | { |
| 199 | columns[len] = new GenericColumnDescriptor(columns[len]); |
| 200 | } |
| 201 | out.writeObject(columns[len]); |
| 202 | } |
| 203 | } |
| 204 | |
| 205 | /** |
| 206 | * Read this object from a stream of stored objects. |
| 207 | * |
| 208 | * @param in read this. |
| 209 | * |
| 210 | * @exception IOException thrown on error |
| 211 | * @exception ClassNotFoundException thrown on error |
| 212 | */ |
| 213 | public void readExternal(ObjectInput in) |
| 214 | throws IOException, ClassNotFoundException |
| 215 | { |
| 216 | int len; |
| 217 | |
| 218 | columns = null; |
| 219 | statementType = (String)in.readObject(); |
| 220 | len = in.readInt(); |
| 221 | if (len > 0) |
| 222 | { |
| 223 | columns = new GenericColumnDescriptor[len]; |
| 224 | while(len-- > 0) |
| 225 | { |
| 226 | columns[len] = (ResultColumnDescriptor)in.readObject(); |
| 227 | } |
| 228 | } |
| 229 | } |
| 230 | |
| 231 | /** |
| 232 | * Get the formatID which corresponds to this class. |
| 233 | * |
| 234 | * @return the formatID of this class |
| 235 | */ |
| 236 | public int getTypeFormatId() { return StoredFormatIds.GENERIC_RESULT_DESCRIPTION_V01_ID; } |
| 237 | |
| 238 | |
| 239 | |
| 240 | public String toString() |
| 241 | { |
| 242 | if (SanityManager.DEBUG) |
| 243 | { |
| 244 | StringBuffer colStr = new StringBuffer(); |
| 245 | for (int i = 0; i < columns.length; i++) |
| 246 | { |
| 247 | colStr.append("column["+i+"]\n"); |
| 248 | colStr.append(columns[i].toString()); |
| 249 | } |
| 250 | return "GenericResultDescription\n" + |
| 251 | "\tStatementType = "+statementType+"\n" + |
| 252 | "\tCOLUMNS\n" + colStr.toString(); |
| 253 | } |
| 254 | else |
| 255 | { |
| 256 | return ""; |
| 257 | } |
| 258 | } |
| 259 | } |
| 260 | |