mirror of
https://github.com/berkeleydb/libdb.git
synced 2024-11-17 09:36:24 +00:00
216 lines
7.7 KiB
HTML
216 lines
7.7 KiB
HTML
<?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>Retrieving Database Items</title>
|
||
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
||
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
||
<link rel="start" href="index.html" title="Berkeley DB Collections Tutorial" />
|
||
<link rel="up" href="BasicProgram.html" title="Chapter 2. The Basic Program" />
|
||
<link rel="prev" href="addingdatabaseitems.html" title="Adding Database Items" />
|
||
<link rel="next" href="handlingexceptions.html" title="Handling Exceptions" />
|
||
</head>
|
||
<body>
|
||
<div xmlns="" class="navheader">
|
||
<div class="libver">
|
||
<p>Library Version 11.2.5.2</p>
|
||
</div>
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">
|
||
Retrieving Database Items
|
||
</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="addingdatabaseitems.html">Prev</a> </td>
|
||
<th width="60%" align="center">Chapter 2.
|
||
The Basic Program
|
||
</th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="handlingexceptions.html">Next</a></td>
|
||
</tr>
|
||
</table>
|
||
<hr />
|
||
</div>
|
||
<div class="sect1" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title" style="clear: both"><a id="retrievingdatabaseitems"></a>
|
||
Retrieving Database Items
|
||
</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
Retrieving information from the database is accomplished via the
|
||
standard Java collections API. In the example, the
|
||
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Set.html#iterator()" target="_top">Set.iterator</a>
|
||
|
||
method is used to iterate all
|
||
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.Entry.html" target="_top">Map.Entry</a>
|
||
|
||
objects for each store. All standard Java methods for retrieving
|
||
objects from a collection may be used with the DB Java Collections API.
|
||
</p>
|
||
<p>
|
||
The <code class="methodname">PrintDatabase.doWork()</code> method calls
|
||
<code class="methodname">printEntries()</code>
|
||
to print the map entries for each database store. It is called via
|
||
the
|
||
<a class="ulink" href="../../java/com/sleepycat/collections/TransactionRunner.html" target="_top">TransactionRunner</a>
|
||
|
||
class and was outlined in the previous section.
|
||
</p>
|
||
<a id="cb_printdatabase"></a>
|
||
<pre class="programlisting">import java.util.Iterator;
|
||
...
|
||
public class Sample
|
||
{
|
||
...
|
||
private SampleViews views;
|
||
...
|
||
private class PrintDatabase implements TransactionWorker
|
||
{
|
||
public void doWork()
|
||
throws Exception
|
||
{
|
||
<strong class="userinput"><code> printEntries("Parts",
|
||
views.getPartEntrySet().iterator());
|
||
printEntries("Suppliers",
|
||
views.getSupplierEntrySet().iterator());
|
||
printEntries("Shipments",
|
||
views.getShipmentEntrySet().iterator());</code></strong>
|
||
}
|
||
}
|
||
...
|
||
|
||
<strong class="userinput"><code> private void printEntries(String label, Iterator iterator)
|
||
{
|
||
}</code></strong>
|
||
...
|
||
} </pre>
|
||
<p>
|
||
The
|
||
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Set.html" target="_top">Set</a>
|
||
|
||
of
|
||
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.Entry.html" target="_top">Map.Entry</a>
|
||
|
||
objects for each store is obtained from the <code class="classname">SampleViews</code>
|
||
object. This set can also be obtained by calling the
|
||
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.html#entrySet()" target="_top">Map.entrySet</a>
|
||
|
||
method of a stored map.
|
||
</p>
|
||
<p>
|
||
The <code class="methodname">printEntries()</code> prints the map entries for any stored
|
||
map. The
|
||
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Object.html#toString()" target="_top">Object.toString</a>
|
||
|
||
method of each key and value is called to
|
||
obtain a printable representation of each object.
|
||
</p>
|
||
<a id="cb_printentries"></a>
|
||
<pre class="programlisting"> private void printEntries(String label, Iterator iterator)
|
||
{
|
||
<strong class="userinput"><code> System.out.println("\n--- " + label + " ---");
|
||
while (iterator.hasNext())
|
||
{
|
||
Map.Entry entry = (Map.Entry) iterator.next();
|
||
System.out.println(entry.getKey().toString());
|
||
System.out.println(entry.getValue().toString());
|
||
}</code></strong>
|
||
} </pre>
|
||
<p>
|
||
This is one of a small number of behavioral differences between
|
||
standard Java collections and stored collections. For a complete
|
||
list see
|
||
<a class="xref" href="UsingStoredCollections.html" title="Using Stored Collections">
|
||
Using Stored Collections
|
||
</a>.
|
||
</p>
|
||
<p>
|
||
The output of the example program is shown below.
|
||
</p>
|
||
<pre class="programlisting">Adding Suppliers
|
||
Adding Parts
|
||
Adding Shipments
|
||
|
||
--- Parts ---
|
||
PartKey: number=P1
|
||
PartData: name=Nut color=Red weight=[12.0 grams] city=London
|
||
PartKey: number=P2
|
||
PartData: name=Bolt color=Green weight=[17.0 grams] city=Paris
|
||
PartKey: number=P3
|
||
PartData: name=Screw color=Blue weight=[17.0 grams] city=Rome
|
||
PartKey: number=P4
|
||
PartData: name=Screw color=Red weight=[14.0 grams] city=London
|
||
PartKey: number=P5
|
||
PartData: name=Cam color=Blue weight=[12.0 grams] city=Paris
|
||
PartKey: number=P6
|
||
PartData: name=Cog color=Red weight=[19.0 grams] city=London
|
||
|
||
--- Suppliers ---
|
||
SupplierKey: number=S1
|
||
SupplierData: name=Smith status=20 city=London
|
||
SupplierKey: number=S2
|
||
SupplierData: name=Jones status=10 city=Paris
|
||
SupplierKey: number=S3
|
||
SupplierData: name=Blake status=30 city=Paris
|
||
SupplierKey: number=S4
|
||
SupplierData: name=Clark status=20 city=London
|
||
SupplierKey: number=S5
|
||
SupplierData: name=Adams status=30 city=Athens
|
||
|
||
--- Shipments ---
|
||
ShipmentKey: supplier=S1 part=P1
|
||
ShipmentData: quantity=300
|
||
ShipmentKey: supplier=S2 part=P1
|
||
ShipmentData: quantity=300
|
||
ShipmentKey: supplier=S1 part=P2
|
||
ShipmentData: quantity=200
|
||
ShipmentKey: supplier=S2 part=P2
|
||
ShipmentData: quantity=400
|
||
ShipmentKey: supplier=S3 part=P2
|
||
ShipmentData: quantity=200
|
||
ShipmentKey: supplier=S4 part=P2
|
||
ShipmentData: quantity=200
|
||
ShipmentKey: supplier=S1 part=P3
|
||
ShipmentData: quantity=400
|
||
ShipmentKey: supplier=S1 part=P4
|
||
ShipmentData: quantity=200
|
||
ShipmentKey: supplier=S4 part=P4
|
||
ShipmentData: quantity=300
|
||
ShipmentKey: supplier=S1 part=P5
|
||
ShipmentData: quantity=100
|
||
ShipmentKey: supplier=S4 part=P5
|
||
ShipmentData: quantity=400
|
||
ShipmentKey: supplier=S1 part=P6
|
||
ShipmentData: quantity=100 </pre>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="addingdatabaseitems.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="BasicProgram.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="handlingexceptions.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">
|
||
Adding Database Items
|
||
</td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top">
|
||
Handling Exceptions
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|