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19
20 package org.apache.james.util;
21
22 import java.sql.Connection;
23 import java.sql.DatabaseMetaData;
24 import java.sql.ResultSet;
25 import java.sql.SQLException;
26 import java.sql.Statement;
27 import java.util.Locale;
28
29 /***
30 * <p>Helper class for managing common JDBC tasks.</p>
31 *
32 * <p>This class is abstract to allow implementations to
33 * take advantage of different logging capabilities/interfaces in
34 * different parts of the code.</p>
35 *
36 * @version CVS $Revision: 494012 $ $Date: 2007-01-08 10:23:58 +0000 (lun, 08 gen 2007) $
37 */
38 abstract public class JDBCUtil
39 {
40 /***
41 * An abstract method which child classes override to handle logging of
42 * errors in their particular environments.
43 *
44 * @param errorString the error message generated
45 */
46 abstract protected void delegatedLog(String errorString);
47
48 /***
49 * Checks database metadata to see if a table exists.
50 * Try UPPER, lower, and MixedCase, to see if the table is there.
51 *
52 * @param dbMetaData the database metadata to be used to look up this table
53 * @param tableName the table name
54 *
55 * @throws SQLException if an exception is encountered while accessing the database
56 */
57 public boolean tableExists(DatabaseMetaData dbMetaData, String tableName)
58 throws SQLException {
59 return ( tableExistsCaseSensitive(dbMetaData, tableName) ||
60 tableExistsCaseSensitive(dbMetaData, tableName.toUpperCase(Locale.US)) ||
61 tableExistsCaseSensitive(dbMetaData, tableName.toLowerCase(Locale.US)) );
62 }
63
64 /***
65 * Checks database metadata to see if a table exists. This method
66 * is sensitive to the case of the provided table name.
67 *
68 * @param dbMetaData the database metadata to be used to look up this table
69 * @param tableName the case sensitive table name
70 *
71 * @throws SQLException if an exception is encountered while accessing the database
72 */
73 public boolean tableExistsCaseSensitive(DatabaseMetaData dbMetaData, String tableName)
74 throws SQLException {
75 ResultSet rsTables = dbMetaData.getTables(null, null, tableName, null);
76 try {
77 boolean found = rsTables.next();
78 return found;
79 } finally {
80 closeJDBCResultSet(rsTables);
81 }
82 }
83
84 /***
85 * Checks database metadata to see if a column exists in a table
86 * Try UPPER, lower, and MixedCase, both on the table name and the column name, to see if the column is there.
87 *
88 * @param dbMetaData the database metadata to be used to look up this column
89 * @param tableName the table name
90 * @param columnName the column name
91 *
92 * @throws SQLException if an exception is encountered while accessing the database
93 */
94 public boolean columnExists(DatabaseMetaData dbMetaData, String tableName, String columnName)
95 throws SQLException {
96 return ( columnExistsCaseSensitive(dbMetaData, tableName, columnName) ||
97 columnExistsCaseSensitive(dbMetaData, tableName, columnName.toUpperCase(Locale.US)) ||
98 columnExistsCaseSensitive(dbMetaData, tableName, columnName.toLowerCase(Locale.US)) ||
99 columnExistsCaseSensitive(dbMetaData, tableName.toUpperCase(Locale.US), columnName) ||
100 columnExistsCaseSensitive(dbMetaData, tableName.toUpperCase(Locale.US), columnName.toUpperCase(Locale.US)) ||
101 columnExistsCaseSensitive(dbMetaData, tableName.toUpperCase(Locale.US), columnName.toLowerCase(Locale.US)) ||
102 columnExistsCaseSensitive(dbMetaData, tableName.toLowerCase(Locale.US), columnName) ||
103 columnExistsCaseSensitive(dbMetaData, tableName.toLowerCase(Locale.US), columnName.toUpperCase(Locale.US)) ||
104 columnExistsCaseSensitive(dbMetaData, tableName.toLowerCase(Locale.US), columnName.toLowerCase(Locale.US)) );
105 }
106
107 /***
108 * Checks database metadata to see if a column exists in a table. This method
109 * is sensitive to the case of both the provided table name and column name.
110 *
111 * @param dbMetaData the database metadata to be used to look up this column
112 * @param tableName the case sensitive table name
113 * @param columnName the case sensitive column name
114 *
115 * @throws SQLException if an exception is encountered while accessing the database
116 */
117 public boolean columnExistsCaseSensitive(DatabaseMetaData dbMetaData, String tableName, String columnName)
118 throws SQLException {
119 ResultSet rsTables = dbMetaData.getColumns(null, null, tableName, columnName);
120 try {
121 boolean found = rsTables.next();
122 return found;
123 } finally {
124 closeJDBCResultSet(rsTables);
125 }
126 }
127
128 /***
129 * Closes database connection and logs if an error
130 * is encountered
131 *
132 * @param conn the connection to be closed
133 */
134 public void closeJDBCConnection(Connection conn) {
135 try {
136 if (conn != null) {
137 conn.close();
138 }
139 } catch (SQLException sqle) {
140
141 subclassLogWrapper("Unexpected exception while closing database connection.");
142 }
143 }
144
145 /***
146 * Closes database statement and logs if an error
147 * is encountered
148 *
149 * @param stmt the statement to be closed
150 */
151 public void closeJDBCStatement(Statement stmt) {
152 try {
153 if (stmt != null) {
154 stmt.close();
155 }
156 } catch (SQLException sqle) {
157
158 subclassLogWrapper("Unexpected exception while closing database statement.");
159 }
160 }
161
162 /***
163 * Closes database result set and logs if an error
164 * is encountered
165 *
166 * @param aResultSet the result set to be closed
167 */
168 public void closeJDBCResultSet(ResultSet aResultSet ) {
169 try {
170 if (aResultSet != null) {
171 aResultSet.close();
172 }
173 } catch (SQLException sqle) {
174
175 subclassLogWrapper("Unexpected exception while closing database result set.");
176 }
177 }
178
179 /***
180 * Wraps the delegated call to the subclass logging method with a Throwable
181 * wrapper. All throwables generated by the subclass logging method are
182 * caught and ignored.
183 *
184 * @param logString the raw string to be passed to the logging method implemented
185 * by the subclass
186 */
187 private void subclassLogWrapper(String logString)
188 {
189 try {
190 delegatedLog(logString);
191 }
192 catch(Throwable t) {
193
194 }
195 }
196
197 }