docs/gsg/JAVA/ReplacingEntryWCursor.html

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   6     <title>Replacing Records Using Cursors</title>
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  17         <p>Library Version 11.2.5.3</p>
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  21           <th colspan="3" align="center">Replacing Records Using Cursors</th>
  22         </tr>
  23         <tr>
  24           <td width="20%" align="left"><a accesskey="p" href="DeleteEntryWCursor.html">Prev</a> </td>
  25           <th width="60%" align="center">Chapter 9. Using Cursors</th>
  26           <td width="20%" align="right"> <a accesskey="n" href="cursorJavaUsage.html">Next</a></td>
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  33         <div>
  34           <div>
  35             <h2 class="title" style="clear: both"><a id="ReplacingEntryWCursor"></a>Replacing Records Using Cursors</h2>
  36           </div>
  37         </div>
  38       </div>
  39       <p>
  40         You replace the data for a database record by using
  41
  42
  43         <span>
  44             <code class="methodname">Cursor.putCurrent()</code>.
  45         </span>
  46
  47
  48
  49     </p>
  50       <a id="java_cursor9"></a>
  51       <pre class="programlisting">import com.sleepycat.db.Cursor;
  52 import com.sleepycat.db.Database;
  53 import com.sleepycat.db.DatabaseEntry;
  54 import com.sleepycat.db.LockMode;
  55 import com.sleepycat.db.OperationStatus;
  56
  57 ...
  58 Cursor cursor = null;
  59 Database myDatabase = null;
  60 try {
  61     ...
  62     // Database open omitted for brevity
  63     ...
  64     // Create DatabaseEntry objects
  65     // searchKey is some String.
  66     DatabaseEntry theKey = new DatabaseEntry(searchKey.getBytes("UTF-8"));
  67     DatabaseEntry theData = new DatabaseEntry();
  68
  69     // Open a cursor using a database handle
  70     cursor = myDatabase.openCursor(null, null);
  71
  72     // Position the cursor. Ignoring the return value for clarity
  73     OperationStatus retVal = cursor.getSearchKey(theKey, theData,
  74                                                  LockMode.DEFAULT);
  75
  76     // Replacement data
  77     String replaceStr = "My replacement string";
  78     DatabaseEntry replacementData =
  79         new DatabaseEntry(replaceStr.getBytes("UTF-8"));
  80     cursor.putCurrent(replacementData);
  81 } catch (Exception e) {
  82     // Exception handling goes here
  83 } finally {
  84    // Make sure to close the cursor
  85    cursor.close();
  86 }</pre>
  87       <p>
  88         Note that you cannot change a record's key using this method; the key
  89         parameter is always ignored when you replace a record.
  90     </p>
  91       <p>
  92         When replacing the data portion of a record, if you are replacing a
  93         record that is a member of a sorted duplicates set, then the replacement
  94         will be successful only if the new record sorts identically to the old
  95         record. This means that if you are replacing a record that is a member
  96         of a sorted duplicates set, and if you are using the default
  97         lexicographic sort, then the replacement will fail due to violating the
  98         sort order. However, if you
  99         provide a custom sort routine that, for example, sorts based on just a
 100         few bytes out of the data item, then potentially you can perform
 101         a direct replacement and still not violate the restrictions described
 102         here.
 103     </p>
 104       <p>
 105             <span>Under these circumstances, if</span>
 106
 107         you want to replace the data contained by a duplicate record,
 108             <span>
 109                 and you are not using a custom sort routine, then
 110             </span>
 111         delete the record and create a new record with the desired key and data.
 112     </p>
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 116       <table width="100%" summary="Navigation footer">
 117         <tr>
 118           <td width="40%" align="left"><a accesskey="p" href="DeleteEntryWCursor.html">Prev</a> </td>
 119           <td width="20%" align="center">
 120             <a accesskey="u" href="Cursors.html">Up</a>
 121           </td>
 122           <td width="40%" align="right"> <a accesskey="n" href="cursorJavaUsage.html">Next</a></td>
 123         </tr>
 124         <tr>
 125           <td width="40%" align="left" valign="top">Deleting Records Using Cursors </td>
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 127             <a accesskey="h" href="index.html">Home</a>
 128           </td>
 129           <td width="40%" align="right" valign="top"> Cursor Example</td>
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