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Import BSDDB 4.7.25 (as of svn r89086)

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Zachary Ware
2017-09-04 13:40:25 -05:00
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Chapter 9. Using Cursors</title>
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.62.4" />
<link rel="home" href="index.html" title="Getting Started with Berkeley DB" />
<link rel="up" href="baseapi.html" title="Part II. Programming with the Base API" />
<link rel="previous" href="dbtJavaUsage.html" title="Database Usage Example" />
<link rel="next" href="Positioning.html" title="Getting Records Using the Cursor" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">Chapter 9. Using Cursors</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="dbtJavaUsage.html">Prev</a> </td>
<th width="60%" align="center">Part II. Programming with the Base API</th>
<td width="20%" align="right"> <a accesskey="n" href="Positioning.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="chapter" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="Cursors"></a>Chapter 9. Using Cursors</h2>
</div>
</div>
<div></div>
</div>
<div class="toc">
<p>
<b>Table of Contents</b>
</p>
<dl>
<dt>
<span class="sect1">
<a href="Cursors.html#openCursor">Opening and Closing Cursors</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="Positioning.html">Getting Records Using the Cursor</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="sect2">
<a href="Positioning.html#cursorsearch">Searching for Records</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="Positioning.html#getdups">Working with Duplicate Records</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="sect1">
<a href="PutEntryWCursor.html">Putting Records Using Cursors</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="DeleteEntryWCursor.html">Deleting Records Using Cursors</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="ReplacingEntryWCursor.html">Replacing Records Using Cursors</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="cursorJavaUsage.html">Cursor Example</a>
</span>
</dt>
</dl>
</div>
<p>
Cursors provide a mechanism by which you can iterate over the records in a
database. Using cursors, you can get, put, and delete database records. If
a database allows duplicate records, then cursors are
<span>the easiest way that you can access anything
other than the first record for a given key.</span>
</p>
<p>
This chapter introduces cursors. It explains how to open and close them, how
to use them to modify databases, and how to use them with duplicate records.
</p>
<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="openCursor"></a>Opening and Closing Cursors</h2>
</div>
</div>
<div></div>
</div>
<p>
To use a cursor, you must open it using the <tt class="methodname">Database.openCursor()</tt>
method. When you open a
cursor, you can optionally pass it a <tt class="classname">CursorConfig</tt>
object to set cursor properties.
<span>
The cursor properties that you can set allows you to
control the isolation level that the cursor will obey. See
the
<i class="citetitle">Berkeley DB Getting Started with Transaction Processing</i> guide for more
information.
</span>
</p>
<p>For example:</p>
<a id="java_cursor1"></a>
<pre class="programlisting">package db.GettingStarted;
import com.sleepycat.db.Cursor;
import com.sleepycat.db.Database;
import com.sleepycat.db.DatabaseException;
import java.io.FileNotFoundException;
...
Database myDatabase = null;
Cursor myCursor = null;
try {
myDatabase = new Database("myDB", null, null);
myCursor = myDatabase.openCursor(null, null);
} catch (FileNotFoundException fnfe) {
// Exception handling goes here ...
} catch (DatabaseException dbe) {
// Exception handling goes here ...
}</pre>
<p>
To close the cursor, call the <tt class="methodname">Cursor.close()</tt>
method. Note that if you close a database that has cursors open in it,
then it will throw an exception and close any open cursors for you.
For best results, close your cursors from within a
<tt class="literal">finally</tt> block.
</p>
<a id="java_cursor2"></a>
<pre class="programlisting">package db.GettingStarted;
import com.sleepycat.db.Cursor;
import com.sleepycat.db.Database;
...
try {
...
} catch ... {
} finally {
try {
if (myCursor != null) {
myCursor.close();
}
if (myDatabase != null) {
myDatabase.close();
}
} catch(DatabaseException dbe) {
System.err.println("Error in close: " + dbe.toString());
}
} </pre>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="dbtJavaUsage.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="baseapi.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="Positioning.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">Database Usage Example </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> Getting Records Using the Cursor</td>
</tr>
</table>
</div>
</body>
</html>